AN A-Z NATURAL HISTORY GUIDE

AMERICAN ANIMALS, PLANTS, MINERALS, HABITATS, LANDFORMS, PHENOMENA, STRUCTURES, CYCLES, TERMS AND CONCEPTS

Aardvark

Orycteropus afer

A strange name for a strange animal. Also called Ant bear and Anteater, the Aardvark is a badger-sized burrowing mammal of the grasslands of southern Africa, having a stocky, hairy body, large ears, a long tubular snout, and powerful digging claws. Not found in North America.

Abalone

Haliotidae

Fairly common along the Pacific coast, these large marine snails creep across rocks, propelled by a large muscular foot, and feed on algae and microscopic animals. Popular with collectors for their pearly, iridescent shells, abalones are also prized by gourmets for their tasty meat. The shell is perforated with a line of small holes along one edge, permitting the expulsion of wastes and the water that is used for breathing. During their first week of life, the tiny free-swimming larvae attach to rocks and other hard objects, and there they mature into adults up to 12 inches long. Although all species are edible, many people consider the red abalone a particular delicacy.

Abdomen

A large body cavity between the thorax (chest) and the pelvic cavity. A strong wall of muscle called the diaphragm, separates the abdomen from the thorax. But no structure separates the abdomen from the pelvic cavity.

Abdomen

Invertebrate term. Hind section of an insect's body; usually appears segmented. The abdomen is the part of the body behind the thorax of insects, crustaceans and certain other kinds of animals without backbones.

Abdominal

Does not refer to the legendary Abominable Snowman. See Abdomen.

Abominable Snowman

Also called Yeti. The Snowman is an obviously mythical creature said to live on Mount Everest and other mountains of the Himalaya range of Asia. Reports of such a creature have also come from remote parts of China and the Soviet Union. According to legend, the Abominable Snowman is a hairy beast with a large, apelike body and a face that resembles that of a human being. It supposedly has long arms that reach to its knees, and it is reported to walk erect on its thick legs. Legend says that the Snowman sometimes attacks villagers. There is no direct evidence that the Yeti exists, even though individuals have photographed “Snowman” tracks in the snows near Everest. In North America, similar reports describe a creature usually known as Bigfoot. See Bigfoot.

Acacia

Acacia

Found in tropical and subtropical regions all around the world, acacias are widespread members of the legume, or pea, family. Only 15 species are native to the United States, but many others have been cultivated successfully, particularly in California and Florida. Growing as either shrubs or small trees, acacias are a source of dyes, tannins, and a gum used in medicines, foods, and manufacturing. Their wood is used for everything from furniture to fence posts. The sweet acacia, a thorny shrub or small tree, is indigenous to Texas and cultivated elsewhere. It favors dry, sandy soils and produces bright yellow heads of tiny flowers in February and March. The fragrant blossoms are used in sachets and as a perfume ingredient. Another species, the catclaw acacia, grows in dense thickets in the deserts of the Southwest. Named for the armament of hooked spines on its branches, the catclaw is decorated with elongated spikes of creamy yellow flowers in early spring and intermittently throughout the summer. The Pima and Papago Indians made a meal, pinole, from its seeds and gathered the honey produced from its nectar.

Accidental

Not regularly occurring in an area; few records existing of sightings.

Accipiter

Short, rounded wings and long tails distinguish the accipiters from all other hawks. Agile woodland birds that alternately flap their wings and then glide, they are sometimes called bird hawks because of their predominant prey, although they feed on insects and small mammals as well. The three species found across most of North America are the foot-long sharp-shinned hawk; the medium-size Cooper's hawk; and the northern goshawk, larger than a crow and formidable enough to kill ducks and rabbits.

Acid rain

Acid rain is a generic term used for precipitation that contains an abnormally high concentration of sulfuric and nitric acid. These acids form in the atmosphere when industrial gas Admissions combine with water, and have negative impacts on the environment and human health. A by-product of automobile exhaust and the combustion of coal and oil in factories and power plants, acid rain has become a serious problem in many areas. It has made many lakes uninhabitable to fish, even in areas far from the sources of pollution. It has killed or damaged trees and crops. And it has corroded masonry buildings and other man-made structures. Acid rain is produced when nitrogen oxide and sulfur dioxide are released into the atmosphere. There they combine with water vapor to form nitric acid and sulfuric acid, resulting in rainfall that is far more acidic than normal precipitation. Emission control devices designed to remove pollutants from smokestacks are available. But they must be more widely used if the problem is to be controlled.

Action and Learning

Action relates to an action or activity, in this case one carried out to provide a particular environmental service to a community. Learning is the increased capacity of citizens to become more ecologically literate and competent.

Advisories Warnings Watches (Weather)

Agencies issue weather advisories, warnings and watches to inform people about current or developing weather. An "advisory" is a bulletin that informs people that actual or expected weather conditions may cause general inconvenience or concern, but do not pose a serious threat. A "watch" alerts people that conditions are favorable for the development of severe weather, while a "warning" tells them that severe or hazardous weather is occurring or highly probable.

Aestivation

An Animal Behavior term, this is dormancy to escape heat during the summer. It is equivalent to Hibernation in the winter. Mainly found in species living in areas such as deserts where drought and very high temperatures make the environment hostile. By becoming torpid in an enclosed and humid burrow, such Animals can conserve both energy and water. Dormancy observed in an animal during summer.

Agate

Valued for their swirling bands of color, agates have long been used in mosaics, jewelry, and other ornaments. The vivid colors for which they are prized, however, are not always the gift of nature; even the ancients knew that these porous stones could be dyed in order to intensify their natural hues. Agates are deposited slowly, layer by layer, in cavities in older rocks. Composed of almost pure silica, they are a type of quartz. Their colorful patterns are caused by minute quantities of iron and other mineral impurities that highlight the concentric bands. In the United States, gemstone-quality agates have been found in Oregon, Washington, and Idaho and around Lake Superior.

Agave

Sometimes known as century plants because they take so long to bloom (not a century, by any means, but often many decades), several species of agaves flourish from Virginia to California. Tolerant of hot, dry growing conditions, they are especially common in the parched deserts of the Southwest. Most agaves consist of a dense rosette of thick, spiny-edged, spearlike leaves up to several feet long. The flowering stalk that eventually emerges from among the leaves may grow to be 20 feet tall and is topped by clusters of tubelike flowers. The blooms are pollinated by long-tongued bats that sometimes hover in the air, hummingbird style, as they lap up the nectar. Some kinds of agave die after flowering, while others bloom year after year. In Mexico the sap and pulp of certain species are used to make the alcoholic drinks pulque, mescal, and tequila. Agaves also are cultivated for their fibers, called sisal and henequen, which are used to make thread and rope. In many areas they are also planted as ornamentals-a tribute to their dramatic beauty.

Aggression

An Animal Behavior term, this is a controversial term and is best used as a loose Categorization of attack and threat behavior but sometimes it is taken to include a much broader group of activities. A Cat attacking a Cause (predatory aggression), a Bird singing (a behavior that tends to repel rivals) and a Human speaking assertively, have all sometimes been described as aggressive. As the causes of these actions probably have little in common with fighting within a species, such broad usage is probably best avoided.

Agonistic behavior

An Animal Behavior term, this is considered to be any behavioral pattern associated with fighting and retreat, such as attack, escape, threat, defense and appeasement.

Ailanthus

Ailanthus altissima

Featured in the novel A Tree Grows in Brooklyn, the ailanthus is a common sight in cities all across the country. Since it easily endures poor soils and air pollution, it thrives where few other trees can grow. A native of the Orient imported to America in the 19th century, the ailanthus is also known as the tree of heaven, a reference to its speedy growth (as much as 10 feet a year) to heights of 60 feet or more. Its featherlike compound leaves are up to three feet long, giving the tree a luxuriant, somewhat tropical look. But its branches are easily broken and its male flowers give off a rank odor, discouraging its use as a street tree. Condemned by many as a rampant weed, the ailanthus nevertheless manages to sprout, unbidden, wherever the wind carries its papery, single-winged seeds.

Air

The air or atmosphere that surrounds the earth is one of the main components of our environment. The air we breathe is part of the mixture of gases-the atmosphere-that envelops the earth and sustains life. It consists of 78% nitrogen, 21 % oxygen, and minute traces of a variety of other gases, including about .03% carbon dioxide. Water vapor also is present in varying amounts, depending on temperature and location. And as any city dweller can attest, air is adrift with a host of microscopic particles, ranging from soot and dust to salt and plant spores. Scientists believe the atmosphere began to form billions of years ago as gases escaped from the earth's interior, mainly through volcanoes. This early atmosphere lacked oxygen, until green plants developed in the ocean and released that vital gas through photosynthesis.

Air pollution

Long recognized as a threat to human health and to the environment, air pollution is a worldwide problem. The contaminants that foul the air range from dust and soot to noxious fumes such as sulfur oxides and carbon monoxide. Among the major sources are emissions from motor vehicles, factories, and power plants. An especially pernicious form of pollution the dense, dark haze known as smog-results when smoke and other gases mix with water vapor in the air. If atmospheric conditions prevent its dispersal, the results can be disastrous. In Donora, Pennsylvania, in October 1948, for example, a slow-moving ridge of warm air hung over the town for days on end, trapping the pollutants from its many industrial smokestacks. By the time the air cleared, 20 people were dead and thousands more suffered serious illness. In recent decades significant strides have been made in cleaning up our nation's dirty air. With stricter emission standards, the installation of pollution-control devices, and other measures, we all will breathe more easily. But much remains to be done before the problem is solved completely.

Air quality

Scientists collect and analyze samples of air in different regions on a regular basis to determine pollutant levels. This information is not only used by decision-makers to pinpoint the sources of air pollution and determine strategies for reducing it, but also to produce daily air-quality forecasts that warn citizens when smog levels are high.

Albatross

The largest and perhaps the most highly adapted of all seabirds, albatrosses glide effortlessly over the waves on stiffly held, very long and narrow wings. Taking advantage of winds and small updrafts, they can remain aloft for hours on end with scarcely a beat of their wings. Indeed, these nomads of the open sea come ashore only to breed, usually on remote islands. Albatrosses live mainly in southern oceans, but a few species visit North American waters. Most often seen is the black-footed albatross, which nests in the central Pacific and appears off the west coast in summer and fall. Dusky brown, with a white face, it has a wingspan of nearly 7V2 feet. The Laysan albatross, with a wingspan slightly shorter than that of its relative, is white with a blackish back, tail, and wings and also is seen in summer off the Pacific coast. It nests in the Hawaiian Islands. In typical albatross fashion, both species feed on fish, squid, and other marine animals, and some willingly accept scraps thrown from passing ships.

Alder

Growing both as shrubs and small trees, alders are found mainly in northern temperate regions. Tolerant of moist conditions, these members of the birch family often grow in dense thickets in swamps and along streams. Although they are of little value to wildlife, the nitrogen-fixing bacteria that live in nodules on their roots play an important role in enriching the soil. Because of their growth habits and their ability to add nitrogen to the soil, alders are useful in preventing erosion and helping reestablish plant growth in fire-scorched areas. The largest North American species, the red alder, reaches heights of more than 100 feet. Reseeding quickly after fires and logging operations, it is the most important hardwood in the Pacific Northwest, where it is used for making both furniture and paper.

Alderfly

Living as adults in the vegetation near ponds and streams, alderflies are named for the trees in which they often congregate. An inch or less in length, these black or dark brown insects have long, threadlike antennae and two pairs of large smoky wings. The adults-sluggish fliers that apparently do not eat-live for only a few days and die soon after mating. The aquatic larvae, on the other hand, live for a year or more underwater, where they crawl along stones and feed actively on other small insects. They come ashore to pupate, burying themselves in the mud, and emerge the following spring for their brief life as mature alderflies.

Algae

These simplest of all plants-they have no true roots, stems, leaves, or flowers-are an extremely varied group. Algae range in size from microscopic single-celled organisms to the giant kelps, seaweeds that grow to lengths of 200 feet or more. They thrive on land, in fresh water, and in the sea and may be green, blue-green, red, or brown. All of them, however, contain green chlorophyll-the substance that enables plants, using sunlight for energy, to make their own food from carbon dioxide and water, a process called photosynthesis. Millions of single-celled algae form the filmy green growth sometimes seen on damp, shaded tree trunks, walls, and roofs. Other microscopic algae live in both fresh and salt water, where they may drift in huge numbers-a very important food source for other forms of life. Common freshwater algae include threadlike spirogyra, found in billowing cottony masses in the quiet water of ponds and ditches, and volvox, which consists of thousands of individuals grouped in spheres the size of pinheads. Diatoms, encased in microscopic glassy shells, are among the most abundant of the marine algae. More commonly seen are the larger types known as seaweeds. Some algae form remarkable associations with other living plants and animals. Lichens, for instance, are dual plants made up of both algae and fungi. Single-celled algae also live inside the tissue of reef-building corals and seem to playa role in the formation of the reef.
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Algae evolution

Close to 2.5 billion years ago, the earth's surface and atmosphere were stable enough to support primitive life. Single-cell organisms began to develop in the seas that covered the planet. Most of them were very simple single-cell bacteria that fed on chemicals in the ocean's waters.

A simple organism known as blue-green algae appeared and spread across the seas. Blue-green algae are still alive today. It was very important to the future of the planet because blue-green algae used sunlight and water to make food, and in the process, created oxygen. As the blue-green algae grew in the earth's seas, they began to fill the atmosphere with oxygen.

The oxygen blue-green algae produced made it possible for other types of organisms to develop. These organisms needed oxygen to carry out their life processes of growth, feeding, responding and reproducing. Unlike the blue-green algae, these organisms could not produce their own food. They needed oxygen to perform their life processes of growth, feeding, responding, and reproducing. In return, they produced CO2, which the algae needed to perform its life processes. A precise balance between plants and animals was established.

Alien

A species that is not native to a particular region but which has been introduced by man and has become naturalized. These imported species are a mixed blessing. Some species have been good additions to American ecosytems. Some species have created severe economic and environmental problems.

Alligator

Alligator mississippiensis

Living relics of the age of dinosaurs, alligators are our largest reptiles. American alligators grow up to 15 feet long and sometimes weigh more than 500 pounds. On land, they are awkward and slow, but in water they are agile swimmers. Their huge jaws and sharp teeth are used not to chew, but to catch and hold prey. Far from fussy feeders, alligators eat almost anything that walks, flies, or swims within their reach, including fish, small mammals, and waterfowl. In spring, bellowing by the males signals the onset of the mating season. The females lay dozens of eggs in large nesting mounds, cover them with vegetation, and guard them until the offspring hatch. Their sex is determined by the incubating temperature of the eggs. If they remain below 86°F, only females develop; if their temperature rises above 93°, all hatch as males. Alligators once were hunted to near extinction, but laws now protect them. In some parts of the Southeast the mighty reptiles again are lords of the lowland swamps and rivers.

Alligator lizard

Five species of alligator lizards are found in the western states, living in habitats as diverse as the humid forests of the Pacific Northwest and the dry grasslands of Arizona. Long-tailed, short-legged, and armored with bony plates beneath the skin, these foot-long reptiles look like miniature versions of their namesake. They all share one characteristic feature-a pleatlike fold of skin along each side of the body that expands after the animals eat and when the females are heavy with eggs.

Allogrooming

An Animal Behavior term, this is mutual grooming between Animals, especially common among primates and Birds. Allogrooming may assist in the care of the body surface because it is often directed to areas the individual cannot reach. Most often it is shown to mates. social partners and dominant individuals, and certainly also has the social function of cementing relationships between individuals.

Allopatric

Bird Biology Avian Conservation term.

Occurring in different places; usually refers to geographical separation of populations. The populations may exhibit divergence in behavior, morphology, or genetic composition.

Alluvial fan

Apron-shaped deposits of sand, gravel, and rock are a familiar sight at the foot of mountain slopes in arid regions. Known as alluvial fans, they are, in effect, deltas on dry land. During the torrential downpours that are characteristic of desert areas, tremendous amounts of debris are swept down normally dry streambeds. Dumped where the river slows down at the base of the mountain slope, the sediments accumulate as alluvial fans.

Alpine biome

Cold, snowy, windy. When you hear those words they make you think of mountains. In Latin the word for 'high mountain' is 'alpes'. That is where today's word alpine comes from.

Alpine biomes are found in the mountain regions all around the world. They are usually at an altitude of about 10,000 feet or more. The Alpine biome lies just below the snow line of a mountain. As you go up a mountain, you will travel through many biomes. In the North American Rocky Mountains you begin in a desert biome. As you climb you go through a deciduous forest biome, grassland biome, steppe biome, and taiga biome before you reach the cold Alpine biome.

In the summer average temperatures range from 40 to 60 degrees. In the winter the temperatures are below freezing. The winter season can last from October to May. The summer season may last from June to September. The temperatures in the Alpine biome can also change from warm to freezing in one day.

Because the severe climate of the Alpine biome, plants and animals have developed adaptations to those conditions. There are only about 200 species of Alpine plants. At high altitudes there is very little CO2, which plants need to carry on photosynthesis. Because of the cold and wind, most plants are small perennial groundcover plants which grow and reproduce slowly. They protect themselves from the cold and wind by hugging the ground. Taller plants or trees would soon get blown over and freeze. When plants die they don't decompose very quickly because of the cold. This makes for poor soil conditions. Most Alpine plants can grow in sandy and rocky soil. Plants have also adapted to the dry conditions of the Alpine biome. Plant books and catalogs warn you about over watering Alpine plants.

Alpine animals have to deal with two types of problems: the cold and too much high UV wavelengths. This is because there is less atmosphere to filter UV rays from the sun. There are only warm blooded animals in the Alpine biome, although there are insects. Alpine animals adapt to the cold by hibernating, migrating to lower, warmer areas, or insulating their bodies with layers of fat. Animals will also tend to have shorter legs, tails, and ears, in order to reduce heat loss. Alpine animals also have larger lungs, more blood cells and hemoglobin because of the increase of pressure and lack of oxygen at higher altitudes. This is also true for people who have lived on mountains for a long time.

Alpine meadow

Perched between forests below and snowy peaks above are the high-elevation alpine meadows of the northern Rockies and other western mountains. The meadows are best known for their annual floral displays: even while the ground remains dotted with snow and ice in spring and summer, they burst into bloom with acres of glacier lilies, bear grass, alpine buttercups, and dozens of other wildflowers. Ptarmigans and rosy finches are among the birds that forage there for seeds and insects, while marmots and ground squirrels are two of the meadows' more conspicuous mammals.

Altricial

An Animal Behavior term, this is used in describing those species in which the offspring are relatively helpless at birth and are kept for a period thereafter in a nest or other hiding place. It is the opposite of Precocial. Some birds and animals are born helpless, and hence completely dependent upon their parents. They will usually remain in the den or nest until they develop to an extent that they become partially independent.

Altruism

An Animal Behavior term, this means conferring a benefit on another individual at a cost to the individual behaving altruistically. In this general sense, altruism includes sharing food and producing warning calls. In these cases, however, the altruist may benefit if the help given is to relatives (as they share a proportion of the altruist's genes) or to social partners who will reciprocate later. Most apparent altruism comes into these Categories and so, strictly, is not altruism at all.

Alpine meadow

Perched between forests below and snowy peaks above are the high-elevation alpine meadows of the northern Rockies and other western mountains. The meadows are best known for their annual floral displays: even while the ground remains dotted with snow and ice in spring and summer, they burst into bloom with acres of glacier lilies, bear grass, alpine buttercups, and dozens of other wildflowers. Ptarmigans and rosy finches are among the birds that forage there for seeds and insects, while marmots and ground squirrels are two of the meadows' more conspicuous mammals.

Amanita

The ghostly white destroying angel and the greenish-yellow death cup are among the many amanita mushrooms that are poisonous. While a few kinds are edible, experts recommend that they all be avoided because of the potentially fatal consequences of a mistaken identification. Fortunately, the amanitas have a few telltale characteristics that make recognition fairly easy. Typically, the stem has a bulbous base surrounded by a fleshy cup and a collar of loose skin near its top. Some of the amanitas have brightly colored caps and make attractive accents on the forest floor. But in the case of these fungi, it is best to look and leave alone.

Amber

Glassy and golden brown, amber has been valued for its beauty since ancient times. Early Romans fashioned it into jewelry, believing that amulets of amber worn at the neck could prevent tonsillitis and goiter; the Greeks wore it as a talisman, claiming it was formed from tears shed by exotic birds. In fact, amber is the fossilized resin of now extinct coniferous trees that lived millions of years ago. Small insects and plants sometimes were trapped in the gummy resin and preserved there when it hardened into amber, providing a glimpse of life long ago. Most of the world's amber comes from the Baltic coast of Europe, but specimens have been uncovered in New Jersey and a few other eastern states.

American copper

Lycaena phlaeas

Only an inch across, this butterfly makes up for its lack of size with brilliance and bravado. Both of the American copper's fiery orange forewings are punctuated by several blackish spots, and the lower borders of the darker hind wings also are bedecked with orange and black. A common sight in the Northeast, this flying flash of color is an unlikely aggressor, chasing off other butterflies and even blitzing dogs and birds.

Ammonite

Some 200 million years ago, while dinosaurs still roamed the earth, ammonites lived in the shallow seas that covered vast areas of present-day North America. Now extinct, these mollusks had coiled, elaborately chambered shells much like those of their descendants, the nautiluses. Most species were a few inches or so in diameter, but a few were huge. One particularly large specimen unearthed from a shale bed in Wyoming was more than five feet in diameter.

Amphibian

Frogs, toads, and salamanders, the most familiar of the amphibians, belong to a well-named group: the word amphibious is derived from the Greek for "leading a double life." And that is what amphibians do. Most begin life in water, swimming and breathing like fish, and mature into four-legged, air-breathing adults. Frogs and toads undergo the most dramatic change, or metamorphosis, from egg to adult. The eggs, deposited in water, hatch into fishlike larvae called tadpoles, with gills for breathing and long tails for swimming. In time, four legs appear, the gills are replaced by lungs, and the tail shrinks to nothing, completing the transition from life in the water to life on land. As the tadpoles of salamanders mature, they too grow legs but keep their long tails. Some develop lungs, others breathe through their skins as adults, and still others retain their gills throughout life and never leave the water. All amphibians are scale less, moist skinned, and cold-blooded. In winter most hibernate underground. Then, in spring, they revive and return to the ponds and streams, where they mate and produce a new generation. Though not so commonly seen as frogs, salamanders actually are more numerous in North America than anywhere else. They are difficult to find because most are active only by night and fond of dark, damp hiding places. But a patient search under rocks or rotting logs in the spring and summer months should turn up a few of these shy and elusive creatures.

Amphiuma

Growing to a length of 30 inches or more and equipped with legs so tiny they are barely noticeable, these brown or grayish salamanders sometimes are mistaken for snakes or eels. Unlike most of their relatives, amphiumas have strong jaws and sharp teeth that enable them to bite fiercely if provoked. They hunt for snails, crayfish, frogs, and fish by night and hide themselves in muddy burrows during the day. The females lay strings of beadlike eggs near the water’s edge, then coil around them until they hatch some five months later. Amphimacer live in swamps, ponds, and drainage ditches in the Southeast, from Virginia to Florida and west to the lower Mississippi Valley.

Amplexus

An Animal Behavior term, this is the posture adopted by pairs of Frogs and Toads during the mating season, with the male riding on the back the female.

Anchovy

Traveling in enormous schools, throngs of these silvery little fish set the water shimmering. They are closely related to herrings and sardines, and like their relatives, they are of great commercial value. Vast numbers are caught annually for use as human food and fish bait, and for processing into fishmeal and fish oil. Feeding on minute plant and animal life called plankton, anchovies are also a vital link in oceanic food chains, for they serve as a major food source for larger predatory fish and seabirds. The kinds most commonly seen in American waters are the northern anchovy, found off the Pacific coast, and the bay anchovy of the Atlantic and the Gulf of Mexico. As short as an inch and a half, and rarely exceeding six inches in length, anchovies are slender silvery fish with a faint stripe along each side. Like most anchovies, both of these American species have large eyes and very large mouths, with the upper jaw protruding beyond the tip of the lower jaw.

Anemone

Anemone

As well known for their seed heads as for their flowers, the anemones have also been given the name of windflowers. Some say they earned this name because their delicate flowers seem to be blown open by breezes; others claim they are so called because their fluffy seeds are easily wafted away on the wind. Members of the buttercup family, the anemones have attractive cup-shaped flowers. (The "petals" are actually showy sepals.) They include many cultivated varieties grown as ornamentals and for the florist trade. A well-loved and widespread wild species is the dainty wood anemone, which bears solitary star like white flowers. In early spring its lovely blooms can be admired in woodlands and meadows across most of North America. Another, the lavender pasqueflower of the western plains, is so named because it blooms around Easter. Indians used to employ its crushed leaves to treat rheumatism and its flowers to stop nosebleeds. It has no medical uses today but is honored instead as the state flower of South Dakota.

Angler

Found in oceans around the world, anglerfish are notable for their unique method of capturing prey. A fleshy, often wormlike flap dangles from a spine on the angler's head and hangs in front of its face. Any fish attracted by this "bait" is quickly snapped up in the angler's huge, toothstudded jaws. So voracious are their appetites that some of the larger anglers have been known to swallow prey almost as big as themselves. The anglers' method of reproducing is as unusual as their feeding habits. By the time they are ready to breed, females are as much as 20 times the size of the stunted males. In some species, the males become permanently attached to their mates and serve only to fertilize their eggs. In other species, the males attach themselves to the females only during the breeding season, and otherwise are able to live independently. The best-known angler is the goosefish, a wide-mouthed monster with a fearsome array of teeth. Though its flesh is delicate and lobsterlike, it is usually considered too gruesome to display intact in fish markets. Its meat is sold under a variety of aliases, including monkfish, angler, and lobsterfish.

Anhinga

Anhinga anhinga

Because they often swim almost completely submerged, with only their heads and long, sinuous necks protruding from the water, anhingas are sometimes known as snakebirds. Their fan shaped tails account for another, less elegant common name-the water turkey. Large, blackish birds of southeastern swamps and marshes, anhingas are well adapted for fishing: they swim and dive easily in search of prey and impale their catch on their slender, sharply pointed bills. (They are, in fact, the only birds that do so; herons and other species with similar bills seize their prey rather than spearing it.) Anhingas then bring their catch to the surface, toss it in the air, and swallow it headfirst. Like their relatives the cormorants, anhingas have loose plumage that does not repel water, and so are often seen perched with their wings spread out to dry. But the easiest way to find them in the trackless swamps they inhabit is to watch the sky: they can be seen soaring gracefully on outstretched wings as they circle high above the treetops.

Animal

Nearly 2 million species of animals have been identified around the world, and their diversity is astonishing; they range from microscopic, single-celled organisms such as amoebas and paramecia to creatures as complex as human beings. Regardless of their size, however, all animals share one common characteristic. Unlike plants, they cannot manufacture their own food; they must instead get their nourishment by eating plants or other animals. Most animals share a number of other traits as well, characteristics related in part to the fact that they must actively seek food. A nervous system and sense organs, for instance, are essential for finding plants or prey. A means of locomotion enables animals to pursue or collect food and to avoid being eaten themselves. And a digestive system extracts nutrients and energy from whatever foods they eat. This diversity of feeding habits helps account for the tremendous variety of animal life. Cats, for example, are skilled predators equipped with muscles, claws, and teeth that would be useless to a nectar-feeding butterfly.

Despite their diversity, all animals are divided into two broad groups, those that have backbones, the vertebrates, and those that do not, the invertebrates. Insects are by far the most numerous animals in either category, with more than 800,000 species known to science.

Animal Behavior-Overview

To the casual observer, animals may seem to pass the time aimlessly-a bird sings from the treetops, a butterfly alights on a flower, a rabbit races across a meadow. But scientists have found that virtually all animal behavior has a purpose. The bird whose song seems so carefree is trying to attract a mate; the butterfly fluttering from flower to flower is searching for food; and the nimble rabbit is fleeing from a predator. Most animal behavior, in short, is tied directly or indirectly to life's most compelling requirement-staying alive.

Animal Behavior

Bluffing and battling

Animals often have to defend themselves against others of their own kind while competing for food, mates, and living space. The security of a home or territory is crucial for mating and rearing young, and each animal has its own way of marking its property and warning others to stay away. The male fox sprinkles urine on stones and trees that border its territory. Other foxes are well aware of these "keep out" signs, but if one should trespass, a conflict of some sort is likely to take place. Usually, though, the encounter is limited to bluffing and threatening until the intruder gives in and is sent on his way. Defense against predators is a different matter, because the fight, if it occurs, is usually a matter of life or death. Teeth, claws, acute senses, and even poisons are used by both predator and prey. Prey species may also defend themselves by running, hiding, or playing dead, or in the case of the armadillo or porcupine, presenting a platelike armor or a formidable array of sharp quills.

Animal Behavior

Animal language

Each animal species has its own language of sound, scent, or display through which it communicates with others of its kind. A male bird may repeat his song thousands of times a day to proclaim his territory or to court a female. And when not singing, birds use call notes to scold, beg for food, summon young, and keep the flock together. Sound is used by many animals: frogs croak, wolves howl, and elk bugle during the rutting season. Among insects, male mosquitoes locate females by the whirring sound of their wings. In the ocean, whales and porpoises have a sophisticated vocabulary of grunts, chirps, whistles, and clicks that scientists have spent years trying to decipher. Some animals use scent to communicate. The feathery antennae of the male moth can detect the scent of a female more than a mile away. Mammals such as deer and badgers use scent glands, urine, or feces to mark their territories. Like humans, some animals use facial expressions and body language to express themselves. Cats and dogs use their mouths and ears to show anger, contentment, or hunger. Members of a wolf pack greet the leader with a ceremonial nuzzle, and he in turn reminds them of his dominance with a gentle nip on the neck. Prairie dogs greet each other with a kiss. And bees do a complicated dance to announce the discovery of a new food source.

Animal Behavior

Rites of courtship

If animals failed to mate, their species would vanish. So the sometimes bizarre and complicated behavior associated with courtship plays a vital role in survival. In most cases, courtship is initiated by the males, many of which go through elaborate rituals to woo their object of desire. The fiddler crab waves an oversized claw at the female, as if to say, "Here I am!" Some male spiders, midgets compared to the females and in danger of being mistaken for prey, announce themselves with intricately choreographed dances; others pluck the female's web like a bass fiddle before coming too close. Some birds, such as hummingbirds, display dazzling colors, while others, like brown thrashers, entice mates with a repertoire of melodious songs. And some of the hawks perform dramatic aerial acrobatics, with pairs locking talons as they swoop through the air.

But seductive displays of color, movement, and song are not the only courting devices. In the ocean, many creatures rely on chemical lures to attract mates. Male oysters, for instance, announce their readiness to spawn by subtly changing the flavor of the water.

Animal Behavior

Learning VS. Instinct

While most animal behavior is instinctive rather than learned, many animals are undeniably able to acquire new skills through training. In the laboratory, rats have been taught to push levers, climb ladders, and negotiate mazes when rewarded with food. And such unusually intelligent animals as chimpanzees and dolphins have demonstrated an almost human ability to learn. In the wild, many young animals learn by imitating adults. During play they copy the hunting and killing maneuvers of their parents, and so develop the strength and timing they will need later in life. Bobcat kittens, for instance, regularly play at crouching, stalking, and ambushing mock prey, as do fox cubs. Still, clear-cut examples of learning are relatively rare in the animal world. For the most part, wild creatures are acting according to instincts or reflexes that have determined the behavior of their species for tens of generations. And such predetermined behavior, however mechanical or predictable, has served them well in the most crucial tasks of life-courtship, self-defense, communication, and ultimately, survival itself.

Animal Ecology

A habitat is any place where a particular animal or plant species lives. Examples of a habitat include a lake, a desert, or forest, or even a drop of water.

All habitats on Earth are part of the biosphere. Since the Earth is always changing, habitats are continually changing as well.

Descriptions of environments using temperature and rainfall are used to group habitats together. Habitats of similar climate and vegetation are called biomes. In different parts of the world, the same biome may contain different species, but will contain similar life forms. For example, trees are the dominant forms of the rain forest, no matter where the rainforest is located.

Animals, which live within a same-species group, and occupy an area at the same time, are part of a population. All members of the same population have certain traits in common. Populations of different plants and animals interact with each other, and together, these populations form communities. Plants and animals in a particular ecological community, or biome, must be adapted to the same living conditions so they can all survive in the same biome.

Many populations can live in the same area because each species fills a specific role in the community. This role is called a niche. What an animal eats, and where it eats are also part of its niche. Giraffes can live in the same area as gazelles because they eat different plants and don't compete with each other. Dung beetles bury the feces of these animals and lay their eggs in it. The hatching grubs feed on the feces. The buried feces also fertilize plants, which in turn feeds the gazelle and giraffe. Each plant and animal has its own niche in the ecological community, and is important in some way to the survival of the other.

Living organisms are usually classified as consumers (animals), producers (plants), or decomposers (fungi), depending on how they get their food. Consumers are, either herbivores, carnivores, or omnivores. Herbivores are called primary consumers because the feed directly on producers. Carnivores feed on other consumers. Omnivores eat both plants and animals. However, animals are seldom completely carnivorous or herbivorous. Some carnivores, such as bears, foxes, and the family cat or dog, will at times eat plants. Herbivores will sometimes eat small insects or grubs as well.

Animism

Biological Philosophy term. Seeing natural objects and phenomena as "animated" by personal spirits. Natural forces like thunder and lightning, streams, trees, the ocean, are given personal existence and treated as gods or demi-gods.

Anisogamy

An Animal Behavior term, this is the situation where germ cells (gametes) differ is size, as found in all higher Animals, the female producing relatively few large eggs and the male many times that number of much smaller sperm.

Annelid

A type of segmented worm.

Annual

Referring to an organism that completes its life cycle from birth or germination to death within a year.

The life spans of flowering plants differ dramatically. The shortest-lived are the annuals, such as corn and sunflowers, which germinate, blossom, set seed, and then die in a single growing season. The biennials, such as carrots and mullein, need two years to mature; they germinate and store food in their first year, then blossom and die in their second. Longest lived are the perennials, which survive for more than two years. Some perennials-peonies, for example-appear to die at season's end, but their underground structures survive to send up new shoots the following spring. Trees and shrubs, in contrast, have permanent woody stems that grow larger with each passing year. A plant that lives for a single growing season.

Annuli

Darkened rings which indicate periods of slower horn growth; can be counted to measure Animal's age.

Anole

Anolis carolinensis

Able to turn from green to brown, green anoles often are mistaken for chameleons. (The true chameleons are old-world lizards.) Males supplement their color by fanning a bright red flap of skin on the throat. Found in swamps and woodlands of the Southeast, these eight-inch climbers have special hooked toe pads used for clinging to branches and even scurrying up walls. Welcomed around homes, anoles earn their keep by feeding on flies and mosquitoes.

Ant

Thriving in almost every dry-land habitat from deserts and beaches to forests and human homes, ants are well known for their industrious ways. Whether exploring for food, toting burdens from place to place, or excavating tunnels, they seem to be constantly busy. Like honeybees, ants are highly social insects and live in colonies that may include thousands of individuals. A colony begins when a winged, fertile female, the future queen, mates in flight with a male. The male then dies, while the female sheds her wings and, in the seclusion of a small burrow, lays her first eggs. The vast majority of her offspring are sterile females, the worker ants whose labors keep the colony going. Eventually, however, some of the eggs develop into males and young queens that mate to form new colonies. The queen does not in any sense "rule" her colony; she just keeps laying eggs, year after year, for the rest of her life, which may last as long as two decades. Ants have a variety of lifestyles. Nomadic army ants, for instance, have no fixed colonies; they march across the land in military columns, feeding as they go. Fungus-growing ants, sometimes called parasol ants, carry pieces of leaf over their heads like umbrellas; they use the leaves to feed the fungi they cultivate as food. Dairying ants "milk" aphids for a sugary secretion called honeydew, and slave-making ants steal pupae from the nests of other species, then raise the kidnapped victims as slaves. Most ants are harmless to humans, but a few are destructive. Carpenter ants can damage buildings by tunneling in the wood. And the imported fire ant builds unsightly nest mounds in pasturelands in the Southeast and attacks livestock with its powerful sting.

Antelope

See Pronghorn

Antelope ground squirrel

Scampering across the desert floor, these frisky little rodents curve their short tail over the back, exposing the white underside. The resemblance to the white rump patch of a fleeing pronghorn antelope accounts for their name. Although antelope ground squirrels are well able to withstand the blistering heat of southwestern foothills and canyons, sometimes they are forced to retreat to their burrows or smear their heads with saliva in order to cool off. Active all year round, they spend their days hunting for fruits, seeds, and insects.

Antennae

Slender, paired sensory organs on the head of an insect or crustacean. Sometimes called feelers, antennae are the paired sense receptors protruding from the heads of a variety of creatures, such as insects, centipedes, crabs, and lobsters. They are sensitive to touch, taste, smell, and in some cases light, temperature, and moisture as well. To animals that possess them, they are as important as eyes and ears are to us. An ant's antennae, for instance, are in constant motion, tapping the ground like a blind person with a cane, pointing into the wind to receive odors, sampling food before it enters the mouth, and greeting other ants with a kind of hello. Depending on species, antennae may look like anything from threads or strings of beads to knobs or gracefully branching feathers. They are usually equipped with thousands of tiny hairs, pegs, or pits that serve as receptors. Bedbugs use their antennae to sense warm objects. The antennae of male mosquitoes can detect the sound of a female's wing beats a quarter of a mile away, while those of moths can sense a mate's odor up to a mile away. Some creatures use their antennae for other purposes as well. Fleas grasp each other with their antennae while mating, certain beetle larvae capture prey with them, and spiny lobsters use them as whips against would-be captors.

Anther

A pollen-containing structure in a flower, located on the end of the male reproductive structure, the stamen.

Antithesis

An Animal Behavior term, this is a principle proposed by Darwin that Animal signals with opposite messages were also opposite in form. For instance, he contrasted a hostile Dog, with erect posture and tail and head held high, with a friendly one, crouching low with its tail between its legs.

Anthropomorphism

Biological Philosophy term. Seeing animals or the world itself as having human characteristics, particularly as having feelings and motives like those of human beings. Everything is like us. See Pathetic fallacy.

Anthropocentrism

Biological Philosophy term. Seeing the universe as centering on humankind, so that everything in the universe is for human beings. Everything is for us.

Antlered

Majestically crowning the heads of deer, moose, elk, caribou, and reindeer, antlers serve both as ornaments and as weapons-primarily among males competing with each other during the mating season. Though they are sometimes used to fight off natural enemies such as wolves, their main purpose is to assert dominance, by means of threats and clashes, over other males of the same species. Antlers first appear when the animal is one or two years old, and are shed and replaced annually. They begin growing in early summer from knobs on the skull and consist of dense connective tissue that later hardens into bone. At first they are covered by a thin, hairy skin called velvet, which allows blood to nourish the developing antlers. As the fall mating season approaches, the velvet dries out, becomes loose, and is scraped off by the animal. In late winter the antlers fall off. They begin growing again in early summer, and the cycle repeats itself. Horns-the headgear of bison, cattle, goats, and other animals-are different from antlers. Both are bony inside, but horns have a hard outer covering similar in composition to fingernails and lack the many spikes and branches that antlers have. Also, horns are not shed but remain on the animal throughout its lifetime.

Antlers

Bony structures that grow from short pedestals on the skull of certain ungulates and are shed annually. During their development the antlers are covered with a hairy skin called velvet which has a rich supply of blood vessels and nerves. Antlers grow from the tips rather than the base (like horns). As the season progresses the antlers become ossified or boney. This ossification finally cuts off the blood vessels and nerves killing the skin and making the antler itchy. This causes the Animal to rub the antlers which removes the skin and exposes the bony surface which has become shiny by the rubbing. Antlers of mature Animals tend to be large and ornate in relation to the Animal's body size. Antlers grow during the summer season and are fully developed by the fall. They are used by the males to assert dominance over other males during courtship rituals in the fall. By December many Animals start shedding their antlers. Shedding is caused by the reabsorption of some of the basal bone which weakens the joint so that the antler falls off if it is knocked.

Ant lion

A wily hunter, the ant lion traps unsuspecting prey in a self-made sandy lair. By moving around in circles in dry sandy soil and throwing sand grains to the side, the little creature, also known as the doodlebug, digs a funnel-shaped pit about two inches wide and one inch deep. Burying itself at the bottom, it lies in wait with only its long pincerlike jaws protruding. When an ant walks by, loose sand at the edge of the pit gives way and more is hurled up by the ant lion, causing the ant to lose its footing and tumble to the bottom. The ant lion then seizes its victim in its jaws, sucks out its juices, and tosses the empty carcass aside. In all, some 60 species of these curious creatures inhabit sandy areas throughout the United States, especially in drier sections of the South. Some, rather than building sand traps, ambush their prey from behind rocks. But whatever their habits, all ant lions are the larvae of delicate flying insects that resemble damselflies.

Aperture

Biology term. The opening of a snail's shell.

Aphid

Seldom more than an eighth of an inch long, aphids are soft-bodied insects that suck sap from plants. They are often known as plant lice because of the damage they do to crops, not only by drinking the sap but also by spreading diseases. Ladybird beetles and their larvae are among the many insect enemies that help keep aphid numbers in check. Some kinds, however, are protected by ants, which feed on honeydew, a sweet, sticky substance excreted by the aphids. The typical aphid's seasonal cycle begins in spring with eggs that have wintered on trees and shrubs. When the eggs hatch, only females are produced, and they in turn give birth only to females. Several generations are born over the course of the summer, with each aphid producing up to 50 daughters in her two or three weeks of life. Finally in the autumn some males are produced. They mate with females, who lay fertilized eggs that can survive the winter and so start the cycle anew the following year.

Appeasement

An Animal Behavior term, this is behavior which inhibits attack in situations where Animals cannot escape or, as during courtship, where it is advantageous for them to do so. Often opposite in form (see the term Antithesis), as well as in the message conveyed, from Threat Displays. Thus, Gulls hide their beaks when appeasing, and then show them in threat. Other appeasing postures derive from juvenile behavior and, in Monkeys, from sexual presentation posture of females. (see the term Lordosis)

Appetitive behavior

An Animal Behavior term, this is used to describe the active searching behavior shown by Animals seeking a goal and is contrasted with the Consummatory Behavior they show when they reach it. When hungry or thirsty, a Rat will explore actively until it finds food or water. Females of many species also become more active when in heat and this makes them more likely to come into contact with males.

Apple

Malus

No one who smells wild apple trees in bloom can ever forget their sweet perfume-George Washington planted some in the shrubbery at Mount Vernon just so he could savor their fragrance. Several species of these wildlings grow throughout the eastern half of the country and up the Pacific Coast from northern California to Alaska. All of our native varieties of wild apples are crab apples, which are relatives of the larger, domesticated apples grown in orchards. Our wild apples come into flower later than the orchard trees, with blossoms ranging from shell pink to pure white, depending on the species. All bear similar fruits, however: about an inch across, they are sweetly scented, hard, and usually a glossy yellow-green. Despite their appetizing aroma, they are too sour to eat out of hand (though deer, black bears, and ruffed grouse relish them). Pioneers made cider and an orange-red jelly from wild crab apples; they also used the trees as understock on which to graft the eating apples they imported from Europe. Nowadays the wild crab apples are more often planted as ornamentals.

Aquatic insects

Ponds and streams are home to an array of aquatic insects, both immature and adult. A few, such as black fly larvae, live attached to the bottom, but most move about in one way or another. Agile water striders skitter across the surface on long, slender legs. Also seen on the surface are large groups of whirligig beetles, which give the appearance of dancing in all directions at once. Back swimmers and water boatmen use their long, oarlike legs to paddle through the water, while dragonfly nymphs dart from place to place by forcing water from their bodies in a kind of jet propulsion. And caddisfly larvae drag along their own self-made mobile homes-neatly camouflaged tubelike cases made of sticks, bits of stone, or leaves. Like their counterparts on dry land, aquatic insects must be able to breathe, and they do so in a variety of ways. The nymphs of dragonflies, damselflies, and mayflies have gills that enable them to absorb oxygen dissolved in the water. The larvae of mosquitoes, in contrast, are snorkelers; they breathe through tiny tubes that reach up to the surface. Still others are like scuba divers, taking along their own oxygen supply; water boatmen, back swimmers, and many diving beetles carry bubbles of air next to their bodies whenever they descend to the depths. Feeding methods are equally diverse. Among the plant eaters are water boatmen, which scrape algae from underwater surfaces. Some of the caddisfly larvae spin silken nets that strain bits of food from the passing current. And many aquatic insects are predators. Dragonfly nymphs have hinged lower jaws that snap out to snatch passing prey, and giant water bugs use their powerful front legs to seize fish and tadpoles twice their size. Thanks to these and other adaptations, aquatic insects are able to thrive in fresh water nearly everywhere.

Aquatic plants

Growing in the water of ponds, swamps, and marshes, aquatic plants have developed a number of strategies for coping with their habitat. Different kinds, for example, are adapted for survival in water of different depths, thus taking advantage of every bit of living space. Plants such as cattails, anchored in mud near the water's edge, and arrowheads, growing in the shallowest water just offshore, are the most like land plants; their roots may be wet, but their leaves are raised out of the water and exposed directly to the sun. Water lilies and pondweeds grow in somewhat deeper water; long stems permit their leaves to float on the surface, faceup to the sun. At still greater depths are plants that grow completely underwater, such as the bladderworts and water milfoil. Finally, there are plants that have lost all connection with the bottom, such as duckweeds, water hyacinths, and even a few ferns; they float freely on the surface, dangling their roots below. The plants that live underwater typically have lacy or strap-shaped leaves-shapes that maximize the surface exposed to sunlight and which are also resilient, preventing damage from any movement of the water. Some of the emergent plants, such as many pondweeds, have bladelike leaves at or above the water's surface and lacy or strap like leaves below. The lacy leaves and stems of underwater plants allow them to absorb oxygen, carbon dioxide, and dissolved nutrients directly from the water. Thus the roots of these plants serve mainly to anchor them in place. Many aquatics have air pockets between the tissues of their stems and leaves, which helps keep them floating. In the case of the water hyacinth, air pockets in the swollen stem serve as pontoons that keep the entire plant afloat. Aquatic plants also rely on water as a medium for dispersal. Some colonize by simply drifting along the surface. Others, such as water lilies, have floating seeds. Sweet flag often spreads by means of broken bits of root that grow into new plants, and waterweed does so with bits of the plant itself.

Aquifer

Layers of porous rock, such as sandstone, retain water that seeps into them from the surface. Resting on impermeable rock layers that prevent the water from flowing any deeper into the earth, these formations, known as aquifers, are capable of holding tremendous quantities of water and serve as natural underground reservoirs. Indeed, wells drilled into aquifers are the primary water source in many areas.

Arboreal

Tree-dwelling.

Arborvitae

Thuja

Slow-growing and long-lived, arborvitaes are handsome conical evergreen trees with fanlike sprays of branchlets sheathed in scaly foliage. Some say that their name, which means tree-of life, refers to their longevity. Others claim the name was provided by the 16th-century French explorer Jacques Cartier; while wintering in Canada, he and his crew were saved from scurvy by a vitamin-rich tea brewed from the tree.

Two species of arborvitae are native to North America. The giant arborvitae, also known as western red cedar, grows in moist soils in the mountains of the Pacific Northwest. Sometimes reaching heights of 200 feet, it has coarse, lightweight wood that is nearly impervious to insects and decay. Indians used it for making canoes, and it still is unexcelled for shingles and siding. Smaller but extremely hardy, the eastern arborvitae, or northern white cedar, is found in swampy areas from Maine to North Carolina. Its wood is valued for poles, fence posts, and lumber, and an oil distilled from its twigs has been used for medicinal purposes.

Arete

The rugged beauty of the Rockies, Cascades, and other glaciated mountains is enhanced by sharp-edged ridges called aretes. They were formed by the continued erosion of adjacent cirques-steep-sided, bowllike, glacier-carved amphitheaters. Glacial erosion enlarged the abutting cirques until finally they were separated only by the narrow, knife-edged wall of rock.

Armadillo

Dasypus novemcinctus

Looking more like a scaly lizard than a furry mammal, the nine-banded armadillo trots about in search of insects, digging them out of the ground or scraping them from leaf litter with its stout claws. The creature, 2 V2 feet long when fully grown, has little to fear from most predators, for its body, head, and tail are encased in hard, bony plates. Its name, bestowed by the Spanish conquistadores, means, "little armored one." In fact, armadillos occasionally defend themselves by curling up into armor-plated balls, but more often they flee to their burrows or dig a new one on the spot. The young are born in spring, with each female always producing a litter of identical quadruplets. The babies are soft shelled at birth, but the bony plates quickly harden, and with eyes already open, the young can walk within hours. Once found only west of the Mississippi, in Texas and neighboring states, armadillos in this century have greatly expanded their range. Nowadays these comical-looking creatures can be seen all the way east to Florida.

Arrowhead

Sagitta ria

Handsome aquatic plants, arrowheads are distinguished by their three-petaled white flowers borne in whorls of three. The commonest species, broad-leaved arrowhead, has extremely long, arrowhead-shaped leaves. But other kinds have leaves that are oval or even strap like, with no resemblance to arrowheads at all. The plants' potato like tubers, once favored foods of many Indian peoples, are responsible for such alternate names as water nut and duck potato.

Arroyo

Steep-sided, flat-bottomed channels are among the characteristic landforms of arid regions, where rainfall is scant and evaporation rapid. Known in the Southwest as arroyos or dry washes, they are the beds of ephemeral streams. Water rushes briefly, often torrentially, down the channels after desert downpours, and then, usually within hours, the streams dry up again. In parts of the Southwest, rain is so infrequent that the arroyos remain dry for most of the year.

Artesian well

Naturally pressurized, artesian wells can produce spectacular jets of water, much like the oil spurting from a gusher. They occur in places where a downward-sloping water-bearing rock layer (an aquifer) is sandwiched between two impermeable rock layers. Rainfall soaks into the upper end of the aquifer, resulting in tremendous water pressure at lower levels. If a well is drilled into the aquifer, this pressure causes water to flow to the surface. Whether drilled by man or flowing naturally through fissures in the earth, artesian wells and springs are important water sources over parts of the Great Plains and in many other areas.

Ash

Fraxinus

Popular shade and timber trees, ashes of several kinds grow throughout the United States. Most are tall, sturdy trees that typically bear featherlike compound leaves in opposite pairs. The trees also produce one-seeded fruits with single, elongated, papery wings that catch the wind. The most common and valuable of the 16 North American species is white ash. Its tough, pliant wood, ideal for baseball bats and other sporting equipment, is also used for tool handles and cabinetmaking. Herbalists and American Indians believed the tree had medicinal properties: tea made from its bark was recommended for a variety of ailments, and its seeds were valued as an appetite stimulant and fever remedy. Blue ash, another species with both decorative and practical uses, is named for the dye derived from its inner bark. A fast-growing, long-lived tree, it can be found in the limestone soils of the Midwest. Much more familiar is green ash, which takes its name from the color of its twigs. The most widely distributed of all the ashes, green ash thrives in moist soils along streams. It is especially abundant in the Mississippi Valley, where its seeds are an important food for quail, turkey, and rodents. Another common species, the black ash, also favors damp places and is named for its dark, almost black, buds. Like some of the other ashes, its wood is often split into strips for weaving into baskets and chair seats.

Aspen

Every breeze makes the aspens come to life with quaking foliage, for their leaves, suspended on long, ribbon like stems, are set to trembling by even the slightest movement of the air. In spring and summer the leaves shimmer with a shiny green on top and a paler gray-green on their undersides, and in the fall they have a luminous golden glow. The aspens' bark, smooth and pale, is often marred with deep black scars- the remnants of claw marks left by passing bears. The trees also are attractive to beavers, which eat the soft inner bark and use the trunks and branches when building their dams and lodges. Foresters classify the fast-growing aspens as "pioneer" trees, since they are among the first to return to abandoned fields and areas scorched by fire. Soft-wooded and brittle, they are of little commercial value but play an important role in anchoring the soil until other trees can reestablish themselves. Only two species of aspens grow in North America. The quaking aspen is common all across the West and Northeast; its taller relative, bigtooth aspen, is found only in the Northeast.

Assemblage

Bird Biology Avian Conservation term.

A set of organisms whose pattern of organization (with respect to competition, predation, mutualism, etc.) is unknown.

Association

Bird Biology Avian Conservation term.

A group of species living in the same place at the same time.

Assortative mating

An Animal Behavior term, this is used mating in which an individual chooses a mate non-randomly in relation to its own characteristics. If positive, the mate chosen is like itself, if negative, it is unlike itself.

Aster

Aster

Taking their name from the Greek word for star, asters do indeed shine brightly, especially in the fall. Although some kinds begin to bloom as early as July or August, the brightest displays of these blue-, white-, or purple-flowered perennials come in September and October. Because the peak of bloom often occurs around the feast of St. Michael, on September 29, our ancestors used to call them Michaelmas daisies.

Asters are found around the world, with more than 100 species native to North America. Almost every state boasts 20 to 30 different kinds, though telling one species from another can be a challenge even for the specialist. Adaptability is one reason for their success: purple New York asters, for instance, can survive even in salt marshes, while others, such as the white heath aster, prefer the parched western plains. Among the most beautiful of all is the New England aster, which, despite its name, flourishes as far south as the Carolinas and westward beyond the Mississippi. Growing to heights of six feet or more, it is covered with masses of two-inch pink to brilliant purple flowers that are true stars of the autumn.

Atlas

Bird Biology Avian Conservation term.

The result of a comprehensive survey of a large geographical area that maps the occurrence (or occurrence and relative abundance) of species in subdivisions of that area. An atlas is usually based on a grid of fixed intervals of distance or degrees latitude and longitude. It is restricted to a particular season of the year, usually the breeding season.

Atmosphere

Compared to the size of the earth, the atmosphere-the layer of air surrounding our planet-is but a thin mantle. Indeed, 99 percent of the air is concentrated within just 20 miles of the earth's surface. Far from uniform, the atmosphere consists of concentric envelopes of air that differ in temperature and composition. The lowest layer, the troposphere, contains about 80 percent of the world's air. Ranging in thickness from 6 to 10 miles, it is the arena in which winds and clouds make up what we call weather. Air temperature in the troposphere decreases with altitude until it reaches a low of about -70OP. Extending up for another 20 miles above the troposphere is the stratosphere, where the temperature rises again to about 32°. Here the sun's rays react with oxygen to form the ozone layer, which serves as a barrier protecting life on earth from damage by the sun's ultraviolet radiation. Higher still is the mesosphere, also 20 miles thick, where temperatures rise and then fall again. Next, some 400 miles high, is the ionosphere, where the sun's rays bombard what little air there is, heating it to more than 1000° and producing electrically charged particles called ions. This ion layer reflects radio waves, enabling us to "bounce" signals around the world. Beyond the ionosphere and extending for thousands of miles into space is the exosphere. There the air molecules are so few and far between that they rarely collide with each other; sometimes they even escape the earth's gravity altogether and drift off into outer space.

Atmospheric science (Science and Technology)

Atmospheric science is the study of the atmosphere, hydrosphere, cryosphere and related environments.

Attention

An Animal Behavior term, this is used to describe a state in which an Animal is more responsive to one aspect of its environment that to others. Experiments have shown that Animals may attend to and learn about some features of a situation and ignore others which are less relevant to them.

Auk

Found only in northern oceans, the 22 species of auks are stocky seabirds that stand upright like penguins. All members of the family are expert divers that use their short wings both for flying and as flippers for swimming in pursuit of fish, shrimp, and other prey. Most auks dress in basic black and white, but during the nesting season a few sport white or yellow plumes on their heads, and puffins are decorated with large, colorful bills. Auks range in size from the 6-inch least auklet of the Bering Sea to the 19-inch thick-billed murre. The giant of the family was the flightless great auk of the North Atlantic; extinct since 1844, it stood 30 inches tall. Auks spend most of the year at sea and come to land only to breed on rocky coasts or offshore islands. Some nest in burrows, others on rocky ledges; the marbled murrelet of the Pacific Northwest sometimes nests in trees. With their seafaring way of life, flipperlike wings, black-and-white plumage, and erect posture, auks are the northern counterparts of the Southern Hemisphere's penguins.

Aurora borealis

Assuming a variety of forms, the sky spectaculars known as the aurora borealis may appear as an eerie grayish glow, as flashing, fanlike bands of green, or even as a dazzling array of multicolored pleats of light draped across the heavens. Also known as the northern lights, the displays are brightest and most dramatic in the far north but are sometimes visible in the lower 48 states. They occur most frequently at times of heavy sunspot activity and are caused by charged particles from the sun hurtling toward the earth's magnetic poles. High in the atmosphere, these particles collide with molecules of air, releasing energy in the form of light. The same spectacular phenomenon takes place near the South Pole, where it is referred to as the aurora australis, or southern lights.

Autumn

Autumn (also known as Fall) is one of the four temperate seasons. It is the transition from Summer into Winter. In America, autumn is the season during which most crops are harvested and trees lose their leaves. It is also the season where days rapidly get shorter and cooler, the nights rapidly get longer, and of gradually increasing precipitation in some parts of the world. Astronomically, some Western countries consider autumn to begin with the September equinox in the Northern hemisphere and the June solstice in the Southern hemisphere. Such conventions are by no means universal, however. Meteorologists count the entire months of March, April and May in the Southern hemisphere, and September, October and November in the Northern hemisphere as autumn.Although the days begin to shorten after the Summer equinox, it is usually in September (Northern Hemisphere) or March (Southern Hemisphere) when twilight becomes noticeably shorter and the change is more abrupt in comparison with the more lingering ones of summer. Autumn is often defined as the start of the school year, since they usually begin in early September or early March. Either definition, as with those of the seasons generally, is somewhat flawed because it assumes that the seasons are all of the same length, and begin and end at the same time throughout the temperate zone of each hemisphere.

Many ancient civilizations computed the years by autumns, noting Autumn's association with the transition from warm to cold weather, and its related status as the season of the primary change from Summer into Winter, i.e., a New Year. This view has dominated in many themes and popular images. In Western cultures, personifications of Autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Most ancient cultures featured autumnal celebrations of the harvest, often the most important on their calendars. Still extant echoes of these celebrations are found in the late-Autumn festivals and holidays. One holiday with its roots as a full moon harvest festival is that of "tabernacles" (huts wherein the harvest was processed and which later gained religious significance), the many North American Indian festivals tied to harvest of autumnally ripe foods gathered in the wild, the Chinese had similar celebrations, as did many others. The predominant mood of these autumnal celebrations is a gladness for the fruits of the earth mixed with a certain melancholy linked to the imminence of harsh weather. Remembrance of ancestors is also a common theme.

Avalanche

The sudden, thundering slide of snow and ice down a mountainside is among nature's most terrifying spectacles. Called an avalanche, it can be triggered by the vibrations from a loud noise or the melting of packed snow by spring rains. Many avalanches occur after heavy snowfalls, when a slick surface develops between the new precipitation and the older snow. In some cases the old snow begins to form dense crystals beneath the new, causing the mass of snow to sweep downhill as if on ball bearings. The cascade of snow sweeps along rocks, soil, trees-anything in its path. Wet avalanches, formed of dense, slushy snow, are treacherous due to their enormous weight and their tendency to freeze upon impact. But dry avalanches, consisting of airborne, powdery snow, are the most devastating-sometimes racing down mountains at over 100 miles per hour. Avalanches are a serious danger to skiers, climbers, buildings, and anything else standing in their way. In order to avert disaster, they often are triggered intentionally at opportune moments, letting the snow slide when it can do the least damage.

Avalanche lily

See Dogtooth violet.

Avens

Geum

Unlike their showy cousins the roses, the avens are rather modest wildflowers. Their blooms, usually an inch or so across, come in yellow, orange, or white. Nodding from stalks one to four feet tall, the flowers of many species mature into burrlike fruits equipped with hooks that hitch a ride by clinging to clothing or to the fur of animals. The long-plumed avens, in contrast, produce fruits with long wispy hairs; reminiscent of feather dusters, they have inspired such colorful alternative names as prairie smoke and old man's whiskers.

Though the various kinds of avens differ in the habitats they prefer and in their seasons of bloom, all share one characteristic-a thick, aromatic root. Indians and colonists boiled the root in water, then added milk and sugar to make a chocolate-flavored drink. Home-brewed ale was laced with avens root, both for the spicy zest it imparted and because it kept the beer from souring. The root was also mixed with wine to produce a cure-all tonic that, as one 19th-century herbalist put it, "restores to health the most shattered and enfeebled constitutions."

Avocet

Recurvirostra americana

Boldly patterned in black and white, American avocets are long-legged, duck-sized shorebirds with slender, strikingly upcurved bills. They are found mainly in the West; where they inhabit marshes and shallow lakes, but occasionally summer on brackish lagoons along the southern Atlantic coast. Avocets use their upcurved bills to forage in a special way that enables them to take food other shorebirds miss. Sweeping their bills back and forth just beneath the water's surface, they catch tiny crustaceans, aquatic insects, and drifting seeds, located with their acute sense of touch. During the breeding season avocets lay three or four eggs in a shallow depression in sand or on firm mud near the water's edge. They provide little in the way of a nest lining, but if the water level rises, the birds quickly build up the nest with sticks or any other debris they can find in order to keep the eggs from being flooded. Often several pairs nest in loose colonies and will come to each other's defense by mobbing any predator that comes too near. Both male and female share in tending the eggs; the male does most of the incubating during the first week, and then the female takes over. The young are downy at hatching and, with their tiny webbed feet, manage to begin diving and swimming within a matter of hours.

Awn

A bristle found in flowers of many grasses.

Axil

The angle where upper surface of a leaf meets the stem on a plant.

Azalea

Rhododendron

Found in a kaleidoscope of brilliant colors, wild azaleas, like their cultivated cousins, are prized for their showy flowers. Often among the first to bloom in spring, these beautiful shrubs add splashes of white, pink, yellow, orange, red, and even lavender to the woodland environments that they prefer. Some of the native azaleas are known as wild honeysuckle, and their funnel-shaped flowers, with long, protruding stamens, do resemble the blossoms of that familiar vine. One pink-flowered species, the Florida pinxter, even mimics the honeysuckle's perfume. Unlike their relatives, the evergreen rhododendrons, which retain their elegant foliage all year round, most azaleas shed their leaves in winter. The only species native to the Pacific Coast is the western azalea, a colorful shrub that flourishes from southern Oregon to southern California. Eastern North America, on the other hand, offers a wider variety of wild azaleas than any other region of the world, with a total of 18 different species.

Back swimmer

Swimming upside down in freshwater ponds and streams and using their long hind legs as oars, back swimmers look very much like tiny rowboats. They often are seen just below the surface and can remain underwater for hours on end because, like scuba divers, they carry along their own supply of oxygen-a bubble of air trapped among hairs on the body. Although they are only half an inch long, back swimmers are fierce predators, willing to attack small fish and tadpoles as well as insect prey. Piercing their victims with their sharp beaks, they suck out the body fluids. They also can pierce a human finger if handled carelessly, causing a painful sting.

Bacteria

Probably the most widespread of living things, bacteria are also the most abundant. A spoonful of garden soil may contain 100 billion of these Single-celled microscopic organisms. Able to survive almost everywhere on earth, some kinds live in the steaming water of hot springs, while others thrive on glacial ice.

Bacteria are responsible for a variety of diseases, such as cholera, tuberculosis, tetanus, and typhoid fever. In plants they cause many kinds of blights and wilts. They are, however, crucial to the existence of all other forms of life. Many benign bacteria inhabit the intestines of animals, helping to digest food and supplying essential vitamins. Others speed the process of decay, recycling nutrients and making them available once again to plants. Still others convert nitrogen from the air into a form that plants can use. Some are even used to prepare foods, including yogurt, certain cheeses, and sauerkraut. Without the ubiquitous bacteria, life as we know it could not exist on earth.

Badger

Taxidea taxus

Found in deserts and grasslands from Ohio to the Far West, badgers are chunky, short-legged members of the weasel family. They grow to about two feet long and can weigh as much as 25 pounds. Except for black feet and black-and white facial markings, their coarse fur is yellowish gray and once was used for making brushes.

Active mostly by night, badgers hunt all year round, although they stay underground in their burrows during the severest winter weather. Their sturdy front claws enable them to dig rapidly-so fast, in fact, that these digging dynamos can escape predators by excavating a burrow right on the spot. Their food consists mainly of small mammals such as mice and ground squirrels, but birds and insects are also taken. It has been reported that badgers may actually form special hunting partnerships with coyotes. The coyote uses its keen sense of smell to locate an underground rodent, the badger digs the animal out, and the two then share the meal.

Mating occurs in summer or early fall, and up to five young are born the following spring on a bed of dry grass in the den where the mother has spent the winter. They are weaned in about six weeks but remain with the mother for several months before setting out on their own.

Badlands

Sharp, toothlike ridges and steep, V-shaped gullies etched into barren, semiarid hills make for "bad lands to cross." And that is exactly how Indians and fur traders long ago described the rugged, nearly impassable terrain covering a vast stretch of southwestern South Dakota. Found in several other places on the Great Plains, these moonscapes were formed by flash floods that stripped away surface soil and vegetation, then gnawed away at layers of weak, easily eroded rock. Our most extensive and scenic badlands area, encompassing hundreds of square miles of spectacular, multicolored cliffs, has been preserved in Badlands National Park in South Dakota.

Bait shyness

An Animal Behavior term, this is used to describe the failure of pest Animals to eat poison put out for them. This may stem partly from neophobia and partly from the avoidance Animals show for foods that have previously made them sick.

Balance of Nature

Biological Philosophy term. The idea that nature, undisturbed by human beings, achieves an ideal balance of different species, that, until it is disturbed, it remains in balance, and that it returns to that state after the disturbance. This is connected to the notion, left over from the time of belief in The Great Chain of Being, that every creature has its place in the harmonious workings of nature and is well adapted to its niche. The mythic notion of constancy survived into a more scientific age, because ecologists were unconsciously applying to ecosystems the physicists' and mathematicians' notions of the stability of mechanical systems. See Carrying Capacity.

Bald cypress

Taxodium distichum

Unlike most conifers, this handsome relative of California's giant redwood is deciduous: in autumn the bald cypress sheds its feathery foliage and remains bald throughout the winter. Equally unusual are its knees, twisted knobs of wood that rise from the roots and stand three or four feet above the surface of swamps, where the tree grows best. Botanists speculate that these strange protuberances may supply air to the bald cypress's waterlogged roots, or perhaps they help to stabilize it on its muddy bed. A characteristic tree of southern wetlands, the bald cypress is typically festooned with silvery clumps of Spanish moss. Common from Florida to eastern Texas, it also ranges as far north as Delaware and up the Mississippi Valley to southern Indiana. The largest tree in swamps throughout its range, it sometimes reaches a height of 150 feet, with a diameter of 12 feet near the base of its swollen, buttressed trunk. Not surprisingly, the wood of this swamp dweller is extraordinarily resistant to decay. Sometimes known as the "wood eternal," bald cypress is valued for uses ranging from greenhouse construction to railroad ties.

Baneberry

Actaea

Clusters of attractive white or crimson berries crown the knee-high stalks of baneberries. But as their name suggests, the pea-sized fruits of these widespread woodland perennials are poisonous. Mice and ruffed grouse eat them with no ill effect, but they can be fatal to humans. Pretty, too, but harmless, puffs of feathery white flowers top the plants from midsummer into fall. The blossoms make the baneberries an appealing choice for woodland gardens and shady spots in rockeries. In many areas the white-fruited baneberries are called doll's eyes because their glossy, ivory colored berries, each marked with a single black spot, seem to gaze up like the eyes of an old-fashioned china doll. Since they also look as if they could be strung on a thread, the plants are known as white beads and necklaceweed as well.

Barberry

Berberis

Attractive throughout the year, the common barberry produces dangling clusters of yellow bell-shaped flowers in the spring. Throughout the summer it wears a cloak of dense green foliage that turns to red in fall. Then it drops its leaves to expose an array of bright red berries that remain on the shrub well into winter. The barberry was imported from Europe in colonial times. Because of its fierce armament of spines, farmers planted it in hedges to protect their fields, and early settlers used its yellow sap for dye and made jellies from the berries. Ironically, this plant is now recognized as an enemy of agriculture. Because it serves as an alternate host for black stem rust, a fungal disease that attacks wheat, oats, rye, and barley, it has been the target of repeated attempts at eradication. In 1726 the colony of Connecticut passed a law calling for its elimination, and now most grain-producing states prohibit its cultivation. Not all the barberries are a bane, however. The Japanese barberry, a popular ornamental, is completely immune to black stem rust.

Bark

The appearance of its bark gives each tree a distinctive signature-so much so, in fact, that experts can identify some trees by their bark alone. Unmistakable, for instance, are the mottled, flaky patterns on sycamore bark and the vertically peeling skin of the shagbark hickory. Bark acquires its telltale textures and patterns because trees, as they grow, become too big for their skins, causing the bark to give way under pressure. And each species has its own way of splitting, peeling, flaking, or shredding on the surface as new bark is added underneath. Botanists distinguish between two layers of bark-the tree's visible outer skin and a soft, thin layer of inner bark. The inner bark is made up of living cells that transport sugars from one part of the tree to another; the much thicker outer bark is composed of dead cork cells that protect the delicate inner tissue. Outer bark must be waterproof to prevent dehydration and tough enough to protect the tree against insects and disease, as well as sun, wind, rain, and ice. For some trees, especially in arid western forests, bark may also serve as fireproofing. Ponderosa pines, for instance, often go unscathed in forest fires thanks to their two-inch armor of corky bark, and the thick reddish bark of the giant sequoias is virtually impervious to flame.

Bark beetle

Sometimes called engraver beetles, these small black or brown cylindrical insects and their larvae dig intricately patterned networks of tunnels beneath the bark of hickories, pines, firs, and many other kinds of trees. The adults first excavate brood galleries, with the females laying eggs at intervals along their lengths. When the eggs hatch, the larvae dig tunnels that branch out in distinctive patterns. After transforming into adults, the beetles emerge from holes at the ends of their tunnels. Some species of bark beetles live only on dead wood, while others attack living trees. Among the most destructive are the elm bark beetles, which transmit Dutch elm disease. The insects themselves do little damage, but they carry a fungus that blocks the elms' water- and sap transporting vessels, causing the trees to die.

Barnacle

Firmly attached to piers, boats, driftwood, seaside rocks, and even whales, barnacles seem as immovable and eternal as the sea itself. Once thought to be cousins of shellfish, they actually are more closely related to lobsters and crabs. They begin life as free-swimming larvae, then glue themselves to underwater surfaces by means of a powerful self-made cement. After forming their limestone shells, barnacles remain fixed to the same spot for the rest of their lives. Only their feathery legs ever protrude from the shell; swaying in the water, they sweep food into the creature's mouth. At low tide, clusters of goose barnacles, looking much like the heads of geese on long, leathery necks, can be seen attached to log pilings. The other familiar type, acorn barnacles, resemble tiny volcanoes and usually encrust rocks. One species of acorn barnacle, found near Puget Sound in Washington, grows to the size of a layer cake and is prized as food.

Barn owl

Tyto alba

Truly creatures of the night, common bam owls spend the day sleeping in hollow trees or hidden among dense foliage. At dusk they venture out, flying silently with mothlike wing beats, to hunt for mice and voles. Aided by facial feathers arranged to channel sound into the ears, their hearing is so acute that the birds can locate and capture prey even in total darkness. As their name implies, bam owls often nest in barns or other buildings, but they also use natural cavities. A clutch consists of anywhere from 3 to 11 eggs, depending on the availability of prey. Since incubation begins as soon as the first egg is laid, each brood includes young of several sizes. If food is scarce, it is the younger nestlings that starve, leaving the older and more aggressive offspring to perpetuate the species. Although bam owls are usually secretive, during the breeding season they proclaim their presence with loud bill snapping during courtship flights. And, as if to announce their coming of age, the young hiss and squeal noisily just before leaving the nest to set out on their own.

Barometric pressure

We live at the bottom of an ocean of air extending many miles into the sky. And the weight of all that air pressing down on us, called barometric pressure, is constantly changing, becoming heavier or lighter depending on the density of the air above us at any given moment. One device that is commonly used to measure atmospheric pressure is the mercury barometer. It does so by balancing the weight of the air with the weight of a column of mercury in a calibrated vertical tube. The top end of the tube is sealed, creating a vacuum, while the bottom end is open, allowing some of the mercury to spill out into a cup exposed to the pressure of the air. When atmospheric pressure rises, the mercury is forced higher into the tube; when it falls, the mercury drops. On the average, air pressure at sea level is 14.7 pounds per square inch, the equivalent of about 30 inches of mercury. A rising or falling barometer indicates impending changes in the weather. Low pressure is associated with clouds and storms, and high pressure with fair skies. Barometric pressure also decreases at higher elevations because less air is pressing down from above.

Barracuda

Sphyraena

It would be hard to mistake a barracuda for any other fish. Torpedo-shaped, with large knifelike teeth and a protruding lower jaw, these fearsome hunters roam warm coastal seas and occasionally venture into deeper water offshore. As they skirt the shallows in search of prey, barracudas are frequently attracted by the glint of moving objects. Many fishermen, reeling in their lines, have seen the steely flash of a barracuda as it slashes at their catch. Divers and swimmers also may be startled by these insistent marauders, though attacks on humans are rare. The Pacific barracuda and the great barracuda, the commonest species, are both fast, voracious predators. Found off the Atlantic and Gulf coasts, great barracudas are the largest of the group, occasionally reaching 6 feet in length. While they are sometimes caught for food, they often carry a toxin that has been known to cause fatal poisoning. Not all barracudas, however, are poisonous; Pacific barracudas, which range from Alaska to California, are a popular food fish on the West Coast.

Barrier island

In the shallow water along some seacoasts, waves and currents deposit long narrow ridges of sand called barrier islands. Standing as buffers between the mainland and the open sea, they are backed by quiet lagoons. Padre Island in the Gulf of Mexico and Hatteras Island, North Carolina, are well-known barrier islands. Though often anchored by vegetation, barrier islands are constantly battered by winds and water; some last only a few years, others a few thousand.

Basalt

Dark and fine-grained, basalt is the most common of all volcanic rocks. It forms when lava rich in iron and magnesium oozes through fissures in the earth's crust and solidifies on the surface. The mineral content of the lava causes the rock's dark color, and rapid cooling on the earth's surface results in its fine texture. Basaltic lava may pile up in the form of volcanoes or create lateral fissure flows that flood vast areas.

Basswood Tilia

When our several species of basswoods come into bloom in early summer, they are enveloped in fragrance and abuzz with the humming of hundreds of honeybees. The trees, in fact, often are called bee trees, since their plentiful nectar produces an especially delicious honey. Also known as lindens and limes, basswoods are popular ornamental and shade trees. Because they are relatively unbothered by diseases or air pollution, they are a familiar sight along city streets in many parts of the country. The trees' fibrous inner bark was traditionally used for making rope, and the soft, white, easily worked wood is excellent for carving. Animals such as rabbits and deer eat both the buds and twigs, while birds and squirrels feed on the dangling clusters of pea-sized fruits.

Bauxite

Named for Les Baux, France, where it was first discovered, bauxite is the ore from which most aluminum is made. It comes in various forms, which may be as soft as dirt or as hard as rock, and its mottled surface is often dotted with pealike spheres. The color also varies; depending on the presence of impurities in the ore, it can range from brown or red to pink or ivory. When wet, soft bauxite gives off a strong smell of fresh earth or clay. Composed mainly of aluminum hydroxide, bauxite deposits are found near the earth's surface and are formed by the weathering of aluminum-rich rocks. The ore is mined with earth movers and dynamite, then shipped to processing plants, where it is refined and smelted into aluminum. Though a number of states contain deposits, most of the bauxite mined in this country comes from Arkansas.

Bayberry

Myrica

Shrubs or small trees that bear clusters of small grayish fruits covered with an aromatic wax, bayberries are also known as wax myrtles and candleberries. The wax can be extracted by boiling the berries in water and has long been used for making scented candles, soap, and sealing wax. The resinous, leathery leaves are sometimes brewed into a tea that herbal healers have traditionally recommended for a variety of illnesses, and the bark of some species is used in a medicine prescribed to ease swelling. The northern bayberry, a shrubby species, is found in the northeastern states, mainly in sandy seaside areas. The southern bayberry, often growing to tree size, ranges from New Jersey south and west to eastern Texas. The Pacific bayberry, yet another well-known species, has dense, shiny evergreen leaves and thrives along the coast from Washington to southern California. Like all the bayberries, its fruits are eaten by myrtle warblers and several other birds.

Bayou

Derived from a Choctaw Indian word meaning stream, bayou is a term applied to some sections of swampy wetland in the Gulf Coast region, especially in Louisiana, Mississippi, and Texas. Often occupying abandoned river channels or oxbow lakes, bayous are filled with shallow, slow-moving, or even stagnant water. Bald cypress trees rise from the sluggish waters, where river otters, amphibians, alligators, and other wildlife reside. Bayou Lafourche, southwest of New Orleans, is among the most extensive of these characteristic southern swamplands.

Bear

Ursus

Of America's three kinds of bears-black bears; brown, or grizzly, bears; and polar bears-the most familiar and most widely distributed are black bears. Our smallest species, averaging about 300 pounds, they inhabit forests and mountainous areas across much of North America. Despite their name, their color varies from cinnamon to black, with a white race found in far western Canada.

The brown, or grizzly, bears once flourished throughout the western half of the continent, but today they are confined to Alaska, western Canada, and wilderness areas south of the Canadian border in the Rocky Mountains. Up to 9 feet from snout to tail and weighing more than 1,600 pounds, Alaskan brown bears are the world's largest flesh-eating land mammals.

The great white polar bears, weighing as much as 1,000 pounds, seldom venture far south of the Arctic Ocean. Accomplished swimmers, they are well adapted for hunting seals on frigid ice floes. Like all the bears, they are very dangerous when threatened or alarmed.

Bears feed on almost anything that is edible and are as fond of berries, roots, and leaves as they are of rodents, fish, and carrion. In the fall they begin to gorge on rich foods in preparation for their long winter sleep. While bears are not true hibernators, they spend the colder months sleeping in dens dug in hillsides, under trees, or in other protected spots. The females give birth to their young in these snug winter nests. The cubs-usually twins-are tiny, blind, and helpless at birth and remain with their mothers for a year or more.

Bearberry

Arctostaphylos uva-ursi

A ground-hugging evergreen shrub with leathery, oval leaves, bearberry ranges across much of North America, forming dense carpets over barren, sandy soils. Clusters of tiny pink or white urn-shaped flowers adorn its branches in spring, and it is decorated in winter with brilliant red berries eaten by birds and bears. Though rather bland and mealy, the fruits are nourishing and were consumed by native Americans, who also mixed the dried leaves with tobacco for smoking. Recommended by herbalists for many ailments, the leaves do in fact contain an astringent that is effective in treating problems of the urinary tract.

Beardtongue

Penstemon

Named for the tuft of colored "whiskers" on the flowers' tonguelike fifth stamen, beard tongues are attractive wildflowers found in most of North America. The trumpet-shaped blossoms may be tiny or up to two inches long; they come in a rainbow of hues, enlivening grasslands and deserts with welcome splashes of color. Some, such as mat beardtongue, are low growers, but most are upright, robust plants topped with clusters of flowers. A large and complex group, the beardtongues are hard to identify precisely, challenging even the experts.

Bear grass

Xerophyllum tenax

Unmistakable and unforgettable, bear grass produces handsome, rounded clusters of creamy white, starlike flowers atop sturdy stalks up to six feet tall. Stands of them, swaying in the breeze, are a common sight in open woodlands and alpine meadows on many northwestern mountains. A closely related species, turkey beard, grows in dry, sandy areas, such as pine barrens, in some of the eastern states. Tufts of long, grasslike leaves, normally tough and unpalatable, grow from the base of the plant. In spring, while still young and tender, they are eaten by bears-hence the name bear grass. Other names include basket grass and squaw grass, alluding to the fact that Indians wove the leaves into clothing and baskets.

Beaver

Castor canadensis

The master builders among North American mammals, beavers were busy erecting their complex dams and lodges while early humans still lived in caves. Propped up by their scaly, paddle-shaped tails, these animal engineers use their chisel like teeth to cut down aspens, willows, and other trees. (The pointed stumps they leave behind are unmistakable signs of their presence.) The logs are then used to dam a stream, creating a shallow pond in which the beavers build a dome-shaped lodge of branches, rocks, and mud. One family, including a pair of adults and several offspring, lives in each lodge. By day they stay inside; at dusk they leave through an underwater exit to cut down more trees, feed on the tender bark, and store branches on the bottom of the pond to serve as a winter food supply. Growing to three to four feet in length and weighing as much as 60 pounds, beavers are our largest rodents. The hind feet are webbed for swimming underwater, where beavers may remain for as long as 15 minutes at a time. At the first sign of danger, an alarmed beaver warns its fellows by slapping the water with its tail as it dives to safety. By the late 19th century, beavers had been trapped to near extinction for their lustrous brown fur. Now protected by law, they have made a dramatic comeback in recent years and are found all across the continent. Some people even consider them a nuisance when their dams flood roads or cropland. But many more praise beavers as water conservationists that also create living space for other animals and plants.

Bedrock

The solid rock which lies buried beneath soil, sand, or gravel (but which in some areas stands exposed at the earth's surface) is known as bedrock. While the type of rock differs from place to place, bedrock is found everywhere and helps determine the contours of the landscape.

Bedstraw

Galium

Sweet-smelling plants that often grow in sprawling mats, bedstraws have a long and varied history of use. According to one legend, the Virgin Mary laid a thick cushion of bedstraw in the manger at Bethlehem. American colonists used the plant as a mattress stuffing, and herbalists have prescribed bedstraws for everything from fading freckles to eliminating kidney stones. Many kinds of bedstraws grow throughout the United States, preferring moist woods and meadows. Most have bristly stems, produce clusters of small white flowers, and bear whorls of four to eight lance-shaped leaves. Cleavers, the best-known species, is named for the prickly little hooks that line its stems and fruits, catching onto anything they touch. Its roasted seeds serve as a coffee substitute, and its vitamin-rich shoots can be cooked for a nourishing vegetable. Another widespread species, yellow bedstraw, grows up to three feet tall and produces long dense heads of bright yellow flowers. Cheese makers traditionally used its leaves and stems to curdle milk, and dyes are extracted from its roots and flowers.

Bee

Of more than 3,500 kinds of bees found in North America, only the well-known honeybees and bumblebees are social insects that live and raise their young in large, rigidly organized colonies. The vast majority are solitary species that lay their eggs in nests provisioned with pollen and nectar and then leave their young to fend for themselves. In contrast to the elaborate, multichambered wax combs of honeybees, the nests of most of the solitary bees are tunnels bored into soil, twigs, logs, and similar places. The tunnel typically is divided into a series of chambers, with a single egg laid on a pollen ball in each cell. A few parasitic species, s1.lch as cuckoo bees, deposit their eggs in the nests of others. Bumblebees, like honeybees, build multiple brood cells of wax, usually in underground chambers such as abandoned mouse nests. Among the most useful of all insects, bees playa vital role in pollinating plants. As they fly from flower to flower gathering pollen and nectar, pollen grains stick to the hairs on their bodies and then rub off on the next flowers they visit, thus fertilizing them. The bees also actively collect pollen for use as food, both for themselves and for their young. They derive added nourishment by inserting their long, tonguelike mouthparts deep inside blossoms and sucking out nectar.

Bee balm

Monarda didyma

In midsummer, the brilliant red blossoms of bee balm are often abuzz with bumblebees. Ruby throated hummingbirds also come to sip the nectar deep in its clusters of tubular flowers. Growing up to five feet tall with fragrant opposite leaves, bee balm is a member of the mint family. Oswego Indians were known to brew a tea from its refreshingly scented leaves, a practice that colonists imitated when real tea became scarce at the time of the Revolutionary War. Still known as Oswego tea in many areas, this beautiful wildflower has a preference for moist, partly shaded soil. It flourishes throughout the eastern part of the country and is widely cultivated as an ornamental.

Beech

Fagus grandifolia

Soaring to heights of 100 feet or more, with a trunk as much as 4 feet thick, the American beech is one of our most magnificent woodland trees. All too often, however, its trunk is disfigured with unsightly scars; its distinctive smooth gray bark seems to be irresistible to vandals, whose whittled initials can mar the tree's unfurrowed bole for decades. Luckily, the beech's bark is not its only attraction. The oval leaves with sawtooth margins have a beautifully silky texture when they first open in spring and, after turning yellow in the fall, often remain on the tree throughout the winter. Its nuts, encased in spiny burs, provide food for a wide variety of wildlife, including foxes, bears, deer, and many kinds of birds. Nutritious and sweet-tasting, they also are enjoyed by humans, whether eaten raw or cooked, or ground as a coffee substitute. Once common across much of eastern North America, the beech in earlier times was often doomed to immediate destruction. Realizing that its presence was a sign of deep, fertile soil, pioneers hacked down beech groves wherever they found them and converted the land to fields for growing crops.

Beechdrops

Epifagus virginiana

Growing just 5 to 16 inches tall beneath their giant host, the beech tree, beechdrops are modest parasites that seem all stems and very little else. From August to October, however, dainty white tubular blossoms striped with purple appear along the upper parts of their slender brownish stalks. Along the lower stems, budlike, self-pollinating flowers produce an abundance of seeds. Although they depend upon beech roots to survive, their host is not harmed.

Beetle

Totaling about 300,000 species, beetles form the largest group of animals in the world, outnumbering all the fish, amphibians, reptiles, birds, and mammals combined. Their extraordinary success stems in part from their great adaptability. Found in nearly every habitat except oceans, they live in the soil, burrow in wood and other plant tissue, and also inhabit freshwater ponds and streams. One species is even capable of tunneling into the lead sheathing of telephone cables. Almost all can fly, though they are rather unskilled compared to other insects. Beetles go through a complete metamorphosis: beginning life as soft-bodied larvae, usually called grubs, they pass through a pupal stage and emerge as hard-bodied adults. The larvae of some species are quite active, moving about in search of prey; others live in the soil, where they feed on roots and other plant parts.

The stiff, shieldlike front wings of adult beetles protect the abdomen and the delicate hind wings, which do the flying. Thus armored, they can burrow into the ground or force their way under logs and stones without injuring their bodies or tearing their wings. Another key to the beetles' success is their chewing mouthparts, which allow them to eat many kinds of food. Most are vegetarians, but some are predators, and still others are scavengers, feeding on everything from dung to clothing fibers. Some, such as the weevils, are very destructive, causing millions of dollars in damage each year to crops and stored foods. Others, such as the ladybird beetles, are highly beneficial, preying on aphids and other insects that are harmful to plants and man.

Behaviorism

An Animal Behavior term, this is used to refer to the school of psychology founded by J. B. Watson, which rejected introspection and stressed the importance of objective observation. Their studies were largely concerned with experiments on learning carried out in highly controlled and simplified laboratory situations.

Bell

A pendant of hair-covered skin that hangs from under the throat of an Animal, e.g., the Moose.

Bellflower

Campanula

Nodding on slender stalks, the delicately flared blossoms of most of the bellflowers look like dainty pastel church bells. Two familiar domestic varieties, which have graced garden plots since colonial days, are Canterbury bells and harebells, also known as bluebells of Scotland. While most of the bellflowers are blue or lavender, Canterbury bells come in pink and white as well. Common wild species include the southern harebell, with clusters of tiny blue bells, and the tall bellflower, with blooms that are starshaped rather than bell-like.

Benthic

Meaning to be found on the floor of lakes, ponds, oceans and other bodies of water.

Berry

Fleshy fruit containing several seeds.

Berry

See Fruit.

Beryl

The radiant emerald and the blue-green aquamarine, two highly prized gems, both are forms of beryl, a mineral found in many parts of North America. Pure beryl crystals are colorless, but most contain impurities, which result in a splendid variety of colors, ranging from red and yellow to blue and green. Not all beryl crystals are of gemstone quality, however; industrial grade beryl is mined for beryllium, an extremely strong, light, versatile metal used by the aerospace industry and in nuclear reactors. Beryl crystals, which are six-sided and very hard, are usually found in granite pegmatite. This coarse-grained rock cools so slowly within the earth that it often produces crystals of enormous size. One stupendous example, unearthed from the Black Hills of South Dakota, was a beryl crystal that weighed 100 tons.

Biennial

A plant that takes two years to complete its life cycle.

Biennial

See Annual.

Bigeye

Small reddish fish with large glassy eyes, bigeyes are found in warmer waters off both the Atlantic and Pacific coasts. Also known as catalufas, they are nocturnal hunters that feed on shrimp, crabs, and other fish. The glasseye snapper bright red with a covering of rough scales-is found from New Jersey to the Gulf of Mexico. The equally colorful popeye catalufa is a well-known Pacific species. Although bigeyes are relatively common, most members of the family are too small to be of commercial value.

Bigfoot

Bigfoot is supposedly a humanlike creature said to live in the Pacific Northwest. Bigfoot has been reported most often in the mountains of California, Oregon, and Washington, and of British Columbia in Canada. Canadians call it Sasquatch. Bigfoot stories resemble those about the Abdominal Snowman, a hairy beast said to live in the Himalaya. Hundreds of people have reported seeing the Bigfoot or its footprints. They describe the creature as standing from 7 to 10 feet tall and weighing more than 500 pounds. Like an ape, it has thick fur, long arms, powerful shoulders, and a short neck. It supposedly walks like a human being and leaves footprints that measure about 16 inches long and about 6 inches wide. Evidence of the Bigfoot’s existence has not been sufficient to convince most scientists. Many scientists believe that some of the evidence, which includes footprints and photographs, has been faked. Bigfoot is apparently similar to the Abominable Snowman, which is also called Yeti. The Snowman is also an obviously mythical creature said to live on Mount Everest and other mountains of the Himalaya range of Asia. Reports of such a creature have also come from remote parts of China and the Soviet Union. According to legend, the Abominable Snowman is a hairy beast with a large, apelike body and a face that resembles that of a human being. It supposedly has long arms that reach to its knees, and it is reported to walk erect on its thick legs. Legend says that the Snowman sometimes attacks villagers. There is no direct evidence that the Yeti exists, even though individuals have photographed “Snowman” tracks in the snows near Everest. See Abominable Snowman.

Bighorn

Ovis canadensis

The Bighorn is a species of wild mountain sheep found only in North America. Male Bighorn sheep have massive horns that curve backward from the forehead, down and then forward. The horns may measure more than 4 feet long, with a circumference of up to about 17 inches at the base. Female Bighorn have very short horns that are only slightly curved. Bighorns are also called Mountain sheep. They live in mountains from east-central British Columbia in Canada to Baja California in northwestern Mexico. Bighorns that inhabit the slopes of the Rocky Mountains and Sierra Nevada are dark grayish-brown in color. Those that live farther south in the mountains of the desert have coats of pale buff.

All Bighorns are creamy-white on the lower parts of their bodies, with patches of creamy-white on their rumps. The size of Bighorns varies, depending on their sex and the regions in which they live. The rams (males) generally are much larger than the ewes (females). In the northern mountains, Bighorn rams may stand up to 3 ½ feet high at the shoulder and may weigh up to 300 pounds. Ewes in this region typically weigh less than 160 pounds. In the desert mountains, rams rarely weigh more than 200 pounds and most ewes weigh less than 120 pounds.

Male Bighorn usually live in groups of 2 to 15 animals. Females and young live in separate groups, usually of 5 to 30 animals. During the mating season, rams often engage in long, spectacular fights. In these battles, which may last for hours, two or more rams repeatedly charge at one another and fiercely crash their horns together. Typically, the male with the largest horns wins.

Ewes bear one lamb about 175 days after mating. Male Bighorn reach maturity at about 7 to 8 years of age. Females mature at about age 4. Bighorns feed on grasses and low shrubs. Their chief enemies include Wolves, Coyotes, and Mountain lions. Bighorns also are endangered by diseases of livestock and by the spread of industrial developments, which have destroyed much of the animal’s habitat. See also Dall Sheep and Stone Sheep.

Billfish

Marlins, sailfish, spearfish-all the members of the billfish family--are prized by sport fishermen, not only for their large size but also for the spectacular battles they wage when hooked. Surging from the water, they leap and violently twist about as they struggle to break free. All are recognizable by their bills, long, swordlike extensions of their upper jaws. (In contrast to the flattened swords of swordfish, which belong to a separate family, billfish bills are rounded in cross section.) Rapid swimmers, some of the billfish have been clocked at speeds of 60 miles an hour. Knifing through schools of mackerel or herring, they stun their prey by thrashing about with their bills, then swallow their victims before they are able to regain their senses. Although they use their bills mainly to stun rather than stab, billfish have occasionally been known to pierce the sides of sharks, whales, and even wooden boats. All the billfish have long dorsal fins, but those of the silvery blue sailfish-very high in relation to the diameter of their bodies-are big and dramatic enough to suggest the great sails of clipper ships. Slender, efficient swimmers, they fold their sails against their bodies when racing through the water. Blue marlin are the heaviest billfish, sometimes weighing more than a ton. Spearfish, less common than marlin and sailfish, are smaller and have relatively short bills. Whatever their size or shape, though, billfish make coveted trophies and are often seen decorating the walls of seaside restaurants.

Biodiversity

The variety of life forms, the ecological roles they perform, and the genetic diversity they contain. The variety from molecular, population, and interspecific levels up to the heterogeneity of ecosystems and landscapes. The variety of organisms found within a specified geographic region. The variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur.

Biogeography

The study of the geographic distributions of organisms, both past and present.

Biological assessment

A document prepared for the Section 7 process to determine whether a proposed major construction activity under the authority of a Federal action agency is likely to adversely affect listed species, proposed species, or designated critical habitat.

Biological opinion

A document that is the product of formal consultation, stating the opinion of the Service on whether or not a Federal action is likely to jeopardize the continued existence of listed species or result in the destruction or adverse modification of critical habitat.

Biological reproduction

Biological reproduction is the process by which new individual organisms are produced. Reproduction is a fundamental feature of all known organisms and each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: Asexual and Sexual. In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to this process. Sexual reproduction requires the involvement of two individuals, typically one of each gender. Normal human reproduction is a common example of sexual reproduction. In general, more-complex organisms reproduce sexually while simpler, usually unicellular, organisms reproduce asexually.

Biological species concept

The idea that species are groups of natural populations that are reproductively isolated from other such groups.

Bioluminescence

An Animal Behavior term, this is used to describe the production of light by Plants and Animals. Bioluminescence may be used in visual displays or, as in some deep-sea Fish, to help in food searching in dark surroundings.

Biomarker

The variation, induced by a substance foreign to the body, in cellular or biochemical components or processes, structures, or functions that is measurable in a biological system or sample.

Biome

An ecosystem usually identified in terms of characteristic forms of vegetation. A biome is the type of habitat in certain places, like mountain tops, deserts, and tropical forests, and is determined by the climate of the place. A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. The climate and geography of a region determines what type of biome can exist in that region. Major biomes include deserts, forests, grasslands, tundra, and several types of aquatic environments. Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.

All living things are closely related to their environment. Any change in one part of an environment, like an increase or decrease of a species of animal or plant, causes a ripple effect of change in through other parts of the environment.

The earth includes a huge variety of living things, from complex plants and animals to very simple, one-celled organisms. But large or small, simple or complex, no organism lives alone. Each depends in some way on other living and nonliving things in its surroundings.

Biosphere

The global realm of all living things.

Biotechnology (Health)

The term used to describe a collection of technologies that use living organisms to create improved products and processes. The primary use of biotechnology from a health perspective is in the development of new medicines, or biopharmaceuticals.

Biotechnology

The term used to describe a collection of technologies that use living organisms to create improved products and processes. These technologies are being used to develop new medicines, to improve yields from fish stocks, forest growth and agricultural crops, to promote energy production from biological sources, to improve treatment of liquid effluents, and to assist in cleanup of wastes and the environment.

Birch

Betula

The bark of the birches is their best-known feature, and rightly so, for it is their most striking characteristic. The smooth, chalky white bark of paper birches is the most familiar, but the bark of other species is equally distinctive. It varies from the silvery yellow of yellow birches to the salmon-pink of young river birches and the shiny, deep mahogany of mature sweet birches. It usually has a papery texture, peeling from the trunk in thin, pliable strips. Twelve species of these handsome trees range far and wide across North America. The cold tolerant paper birch grows north to the edge of the Arctic tundra, while the river birch flourishes as far south as Louisiana. Widespread in the west is the water birch, named for its fondness for damp soils. Another species, the gray birch, thrives on soils too poor for most other hardwoods; in New England, stands of this so called "poverty birch" almost always mark the worn-out fields of abandoned farms. All birches are pioneer trees. Producing tiny, winged seeds so light that they can drift for miles on the wind, the birches are among the first trees to colonize land that has been stripped by fire or logging. In a relatively short time, thick stands of fast-growing, colorful birches hide the scars of man's misuse while protecting the soil against erosion.

Bird

Warm-blooded, feathered, egg-laying vertebrates that have a beak and wings, and are usually able to fly. Unique among all animals in having feathers, birds are the most widespread and numerous land-dwelling vertebrates. Of the roughly 9,100 species of birds in the world, about 850 have been found in North America and some 650 of these nest here regularly. The number of individual birds in North America has been estimated at 5 to 6 billion. Among the most abundant species are the redwinged blackbird, the European starling, and the common grackle, each probably numbering more than 100 million. Runners-up include the American robin, the yellow-rumped warbler, the song sparrow, and the brown-headed cowbird. Among the rarest are the whooping crane and Kirtland's warbler, each with a population of less than 200. The ivory-billed woodpecker and Bachman's warbler, if not already extinct, are even rarer. Our tallest bird, the whooping crane, stands almost five feet high. The record wingspan, at nine feet seven inches, belongs to the endangered California condor. The heaviest is the male trumpeter swan, which weighs as much as 38 pounds, while the smallest is the Calliope hummingbird, at 2314 inches long and weighing only a fraction of an ounce. Except for the extinct great auk, all North American birds known in historic times have been capable of flight. Indeed, flight is one of the characteristic features of birds, and many of their adaptations are related to this ability. Chief among these are feathers, which, being light and strong, serve the needs of flight very well. The large feathers of the outer wing propel the bird through the air, and the curved flight feathers of the inner wing provide lift. Those of the tail aid in steering by acting as a rudder, while the feathers of the body, known as contour feathers, form a smooth surface that offers little drag, or resistance, to the flow of air. Feathers also provide insulation, important for animals that must maintain high body heat and conserve energy to meet the demands of flying. Other adaptations for flight include an internal system of air sacs that lower the ratio of weight to volume. The air sacs also allow oxygen rich air to pass through the lungs during both inhalation and exhalation, another way of meeting the energy demands of flight. Eggs that develop rapidly and are incubated outside the body also contribute to weight reduction. The reproductive system, moreover, is active and enlarged only during the nesting season; after breeding it shrinks drastically both in size and weight. In addition, birds have a rigid skeleton, which provides a solid base for the powerful breast muscles that drive the wings. Some of the bones are hollow and so help to reduce weight. Finally, birds are equipped with senses- including large, keen eyes- that allow them to operate skillfully in the air. Birds have many different flight styles, from the effortless gliding and soaring of vultures, hawks, and eagles to the hovering flight of hummingbirds. Petrels, shearwaters, and albatrosses take advantage of subtle air currents over the ocean, conserving energy by riding on small updrafts over the waves, just as larger birds make use of updrafts over open country or mountainsides. Woodpeckers, starlings, and finches fold their wings during flight, which results in a bounding flight style. Finally, many birds fly with steady, powerful wing beats, often in wedge-shaped formations that allow each bird to ride on the turbulence of the one in front of it. Flight in many cases is important in obtaining food. Swallows, swifts, and night jars capture insects in midair, and hummingbirds use their hovering abilities to get at the nectar in flowers. Hawks and eagles soar over vast areas searching for prey, and flycatchers dart out from perches to snap up passing insects. The bills of birds reflect their methods of foraging and so show many adaptations. Hawks and owls use their hooked bills for tearing flesh. The conical bills of finches, sparrows, grosbeaks, and buntings are ideal for crushing seeds. Hummingbirds and some sandpipers use their long, slender bills for probing, while the bills of flamingos and many kinds of ducks are specially formed for filtering food from water. The fish catching herons, the anhinga, and the northern gannet, in turn, have spear-shaped bills, and woodpeckers have chisel like bills that are ideal for hacking holes in tree trunks. A number of other birds such as crows and jays, noted for their varied diets, have all-purpose bills. Habitats are varied, too, for no other group of animals has been so successful in reaching and adapting to so many different environments. From the highest mountain peaks to expanses of ocean thousands of miles from any coastline, birds have found ways of obtaining sufficient food and, in many cases, of nesting. Except for fish, the vertebrate that lives closest to the North Pole in winter is the common raven, which ranges all the way to northern Greenland and the islands of the Canadian Arctic. Many species make their home in America's harshest deserts, and even the most barren salt flats have their pairs of snowy plovers. Because birds are conspicuous and attractive, concern for their well being has always been important in conservation movements. They are easy to see and count, and any drop in their populations is easily detected. Birds thus provide an early warning system, often the first indication we have that something is wrong with the environment. Declines in ospreys, bald eagles, and peregrine falcons provided a clue that DDT and similar chemicals, all of them potentially harmful to humans, were building to dangerous levels in wetlands. As a result of this research with birds, these chemicals are now controlled or banned. Today, declines in migrant songbirds in North America's woodlands signal the destruction of the tropical rain forests where these species spend the winter. Birds thus are not merely conspicuous and beautiful. They are valuable allies in our efforts to save our planet.

Birding (Recreation)

Bird-watching is a popular hobby. Many birders assist organizations in monitoring bird populations through annual counts.

Bison

Bison bison

When Europeans first reached North America, bison by the tens of millions roamed the continent. Most lived on the Great Plains, where several tribes of Native Americans hunted them for meat. Their hides were used for clothing and shelter, and their horn and bone for utensils. Buffalo, as these magnificent grazers are sometimes called, are unmistakable-with their huge, horned head, massive neck, and high, humped shoulders. A thick, dark, shaggy cape of hair, often matted and mudcaked, hangs from the head, neck, and forelegs. Bulls stand about six feet tall at the shoulder and can weigh more than a ton, while cows average about 900 pounds. During most of the year, cows and calves live in family groups, but bulls join them during the summer to compete for harems that range from 10 to as many as 70 cows. Slaughtered for sport, food, and as part of a campaign to subdue the Native Americans, the bison were eventually reduced to near extinction. By 1890, fewer than 1,000 of the animals had survived. Now protected in parks and reserves, bison number about 50,000 and are a treasured part of our natural heritage.

Bittern

At home amid the reeds and cattails of freshwater and brackish marshes, American bitterns are skilled camouflage artists whose streaky brown plumage helps them blend into their surroundings. Whenever they sense danger, these masters of deception all but disappear by stretching their necks and long bills skyward, mimicking the vegetation. They even waver gently when breezes ripple the reeds. American bitterns, at two to three feet long, are the larger of the two North American species, which are related to the lankier, longer necked herons. Thanks to their bellowing springtime calls, they are also known as thunder-pumpers and bog bulls. Their smaller cousins, least bitterns, are only about one foot long and utter a more subdued cooing note. Both species build clumsy nests on the ground near water and lay clutches of three to five eggs. They feed on a wide variety of aquatic animals, including fish, frogs, tadpoles, and insects. Though sometimes seen flying low over marshlands, these secretive birds seldom fly any great distances except during migration.

Bitterroot

Lewisia rediviva

Though it grows only three inches tall, bitterroot nevertheless makes a bright display on arid western mountain slopes from late April into July, for each plant produces a virtual bouquet of spectacular pink to whitish blooms. Native Americans no doubt admired the show, but they did not pick the flowers. They harvested the thick fleshy roots instead and, after paring away the bitter red bark, roasted them like potatoes or boiled them in soups and stews.

Bittersweet

Celastrus

Many people cherish bittersweet as a highlight of the autumn landscape, for it is then that the orange husks of its showy fruits burst open to reveal the bright red seeds within. They may look inviting, but despite the plant's name, bittersweet fruits are not edible. Two species of these twining vines are common across much of the United States. The native American bittersweet thrives in moist, shady spots from Quebec to North Carolina and west to New Mexico. It rambles happily over stone walls and fences, and up shrubs and trees to a height of 60 feet. The other kind, oriental bittersweet, has escaped from gardens and become naturalized along the eastern seaboard. Its fruits are similar to those of the American species, but the clusters are smaller and hidden among the foliage.

Bivalve

A mollusk whose shell comprises two halves.

Black bass Micropterus

Several species of freshwater bass, known collectively as black bass, are native to cooler streams in eastern North America. Unrelated to striped bass or the sea bass, they are members of the sunfish family-and most are just as pugnacious as their smaller kin. Because they are such strong, tenacious fighters, the two best-known species-largemouth bass and smallmouth bass-have been introduced into lakes and rivers all across the country. They are in fact among the most popular of our freshwater game fish; armies of anglers try to deceive them with a seemingly endless array of artificial lures. Largemouth bass may grow to three feet in length and weigh more than 20 pounds-twice the size of smallmouth bass. Even so, the two fish are often mistaken for one another since their coloring-olive above with silvery undersides-is so similar. The best distinguishing feature is the mouth, which on largemouth bass extends back beyond the eye. During the heat of the day, bass stay in deeper water, swimming among the rocks and preying on crustaceans and small fish. In the evening, they move into the shallows to feed on insects and other creatures near the water's edge.

Blackberry

Rubus

It seems only fair that wild fruits as delectable as those of the blackberries should be well-guarded, hidden among thickets of thorny canes. Blackberries, though, are a tangle in more ways than one. Botanists argue endlessly about the number of species there are-one count runs to 122. They probably will never agree, since blackberries cross easily with their close relatives the raspberries and dewberries to produce a continual stream of new hybrids. The denizens of field and forest do not worry about the scientific status of the fruit; they are too busy eating it. Animals from chipmunks to grizzly bears rely on blackberries as a major part of their summer diet. Some of these foragers even view the thorns as an asset- many small birds rely on them as protection for their nests.

Blackbird

Of the five kinds of blackbirds found in North America, the best known and most widely distributed are red-winged blackbirds (or redwings), named for the males' bright red wing patches, bordered with a band of yellow. Nesting in marshes across most of North America, the males stake out their breeding territories with a con-ka-ree call familiar to many as one of the earliest signs of spring. In winter, the redwings and other blackbirds gather in such enormous flocks (sometimes numbering in the millions) that they threaten crops and even destroy the trees on which they roost. Tricolored blackbirds resemble redwings, but the males' wing patches have a white border. They are found only in California and Oregon and live year-round in huge, dense colonies. Yellow-headed blackbirds, ranging from the Great Lakes to the Pacific, often breed in the same marshes as redwings. But the two do not compete for living space, since yellow-headed blackbirds tend to nest over deeper water. The other two species, rusty blackbirds and Brewer's blackbirds, lack any patches of red or yellow. Both nest in trees or shrubs near water; the rusty prefers conifers in northern forests and bogs, while the Brewer's often breeds in western towns and parks. The females of all the blackbirds, drab compared to the males, take charge of nest building and incubation. They fashion sturdy, cupshaped nests, firmly anchored to reeds, bulrushes, or branches, and lay an average of four to six eggs. In most cases, the males have more than one mate.

Black fly

Simulium

Only about an eighth of an inch long, humpbacked black flies nevertheless are determined aggressors; attacking man and beast alike, they can inflict painful, sometimes bloody, bites. Their yearly cycle begins in early summer, when adult females lay masses of eggs in fast-flowing streams and rivers. The wormlike larvae attach themselves to rocks by means of sucking disks on the ends of their bodies, and they filter bits of food from the water flowing past. Sometimes the larvae are so numerous that their densely packed bodies look like mossy mats on the rocks. Eventually encasing themselves in cocoons, the legless wrigglers are transformed into adult flies that go swarming through the north woods- much to the dismay of summer campers. Common examples of these noxious pests are the Adirondack black fly, the buffalo gnat, and the white-stockinged black fly.

Black rat

Rattus rattus

Along with its cousin the Norway rat, this aggressive, adaptable rodent has been man's uninvited companion for centuries. The two rats, both immigrants from the Old World, are similar in appearance, but black rats have longer tails, larger ears, more-pointed noses, and darker fur. Unlike the more widely distributed Norway rat, black rats in the United States are restricted mainly to the southern states and seaport cities. Living in or near buildings, they reproduce rapidly and feed by night, usually on human food supplies. Good climbers that like to nest above ground, black rats tend to occupy the upper floors of buildings, while Norway rats prefer ground floors, basements, and sewers. Both species carry diseases, but the black rat is especially notorious for its role in bringing the bubonic plague to medieval Europe.

Black widow spider

Latrodectus mactans

The most poisonous spider in North America, the female black widow produces a powerful venom that causes severe pain and occasionally even death. Shiny black, she is easily recognized by the red hourglass-shaped mark on the underside of her pea-sized abdomen. (The harmless male is less than half the size of the female.) Although the black widow spider ranges across much of the country, it is most common in the south and is usually found in damp, dark places. It earned its name from the female's habit of eating the male after mating, despite the fact that such cannibalism also is practiced by many other kinds of spiders.

Bladderwort

Utricularia

Carnivorous plants with no roots and, in some species, no true leaves, the bladderworts grow in swamps and ponds, where they feed on small animal life. Scattered among the stems and leaves are tiny bladders that function as traps. A watertight door seals the bladder's entrance, and glands pump out any water inside to create a partial vacuum. When an animal touches trigger hairs on the door, the seal breaks and a stream of water rushes in, along with the hapless prey.

Blazing star

Liatris

The nomadic Indians of the northern plains used to wait anxiously each year for the late summer blossoming of the blazing stars. They knew that the appearance of the purplish spikes of thistlelike flower heads, also called gayfeathers, coincided with the ripening of the corn in the fields of neighboring tribes and so marked the beginning of a time of feasting. Though blazing stars of several species grow as far east as the Atlantic Coast, these hardy perennials are uniquely suited to life on the prairie. One kind, for instance, sends its roots a yard or more into the soil during its first season of growth, making the modest above-ground seedling almost invulnerable to drought.

Bleeding heart

Dicentra

Set amid lacy, finely cut foliage, the pink, heartshaped blossoms of the eastern and western wild bleeding hearts look for all the world like old-fashioned valentines. Just as descriptively named are their near relatives: Dutchman's breeches, which resembles trousers hung out on a line to dry, and the western steer's head, which looks uncannily like a skull with horns. But beware; despite their charm, several of these plants are also known as staggerweed because of the stupefying effect their toxic foliage has on unwary deer and cattle.

Blenny

Living in tidepools and other shallow waters, blennies are a diverse group of small, slender marine fish. Most are only a few inches long, with a spiny back fin extending from head to tail, and many have branched tentacles and "hairs" on their heads. Some of them, known as the scaled blennies, are predators, while the scaleless combtooth blennies use their teeth to scrape algae from rocks and coral. Some of the blennies use their two front fins as limbs for crawling along the bottom and can even pull themselves out of the water to bask on spray soaked rocks.

Blizzard

Although any heavy snowstorm is commonly called a blizzard, in its strict sense the term refers to a storm with abundant snowfall, wind speeds of 35 miles an hour or more, and temperatures of 20°F or less. Large, dunelike drifts usually form, blocking roads and piling up around buildings, and strong gusts sometimes blow so much snow through the air that visibility is reduced to just a few feet. While storms of this kind most often occur on the northern Great Plains, the most famous blizzard of all blasted the northeast from March 11 to March 14, 1888. Winds during the Blizzard of '88 gusted to 85 miles an hour, and the temperature dropped to zero. In some places snow fell for 48 hours, and in New York City it reached a record depth of 20.9 inches. More than 400 people lost their lives as a result of the storm. The Blizzard of '88 was fed by moisture from the Atlantic Ocean, but the Great Lakes spawn blizzards, too. One of the worst in modern times struck Buffalo, New York, on January 28, 1977. Driven by 70-mile-an-hour winds, snow fell for three days and, with nearly 3 feet of snow already on the ground, drifts reached heights of 30 feet. The death toll was 29, including several people who were trapped in stranded cars.

Bloodroot

Sanguinaria canadensis

Cherished as a harbinger of spring, bloodroot is among the first flowers to appear in eastern woodlands. Its blossoms, pure white or pinkish, are each borne singly at the end of a stem, with the stalk enfolded in a large blue-green leaf. In 1612, Captain John Smith, leader of the Jamestown settlement, commented on bloodroot, noting that it bore a root "the bignesse of a finger and as red as blood." The color was in the sap, which Indians throughout the plant's range, from New Brunswick to Florida and west to Oklahoma, used as a dye to paint their faces, clothes, and weapons. In more recent times, scientists found that an extract of the root helps control dental plaque, and it is the basis of a toothpaste and oral rinse now offered for sale.

Blowhole

When tides are high and seas strong, spectacular fountains of spray can sometimes be seen shooting through vents in the cliffs along rocky shores. The openings, called blowholes, are gaps in the roofs of caves carved by the steady assault of battering waves. At high tide the ocean rushes into the caves, and successive surges force jets of water up through the blowholes.

Bluebell Mertensia

Of the many bluebells native to the United States, most inhabit high meadows and rocky slopes on our western mountains. Far more familiar to most of us is an adaptable lowland species, the Virginia bluebell, which flourishes in woodlands and wet fields from New York to Minnesota and south to Alabama. Also widely cultivated in gardens, the Virginia bluebell is a seasonal treat that shows its colors only briefly. Bursting from the soil as a tightly wrapped, bluish clump of leaves on the first warm days of spring, it unfurls its foliage and sends up stalks topped by clusters of pinkish buds that open to porcelain blue, bell-shaped flowers. Then, in just a few weeks, the whole plant withers and hides underground until the following spring.

Bluebird

Sialia

With their bright blue feathers and cheerful songs, our three species of bluebirds are a welcome presence in fields and gardens across the country. The most widespread, ranging from the Atlantic Coast to the Rocky Mountains, is the eastern bluebird, which has a rust-colored breast and throat. The western bluebird, similar in appearance but reddish on its back as well, lives only in the Far West. And the all-blue mountain bluebird prefers the higher elevations of western mountains. Bluebirds feed primarily on insects in summer and berries in fall and winter. Scanning the ground from fence posts or other perches, they dart down and pounce on insect prey. The mountain bluebird uses a more aerial technique; it often catches insects on the wing or, hovering in midair, drops down to snatch insects it has spotted on the ground. Found mainly in areas with scattered trees, all three bluebirds are hole nesters. They commonly take over abandoned woodpecker nests, but the mountain bluebird sometimes chooses rocky crevices as well. Like most hole nesters, they willingly accept bird houses. In many areas the bluebirds have declined in numbers. Biologists believe this is due in part to human activities. But the main factor seems to be competition with other hole-nesting birds, especially those two imported aliens, the house sparrow and the starling.

Bluebonnet

Lupinus

The much-beloved symbol of Texas, these wild lupines are expansive as only Texans can be, their spikes of clear blue blossoms mirror the sky for miles along Texas highways from spring into early summer. (Of the four species of bluebonnets found in Texas, the official state flower is the little Lupinus subcarnosus.) A simple device helps these prairie wildflowers succeed in the difficult southwestern climate: their seeds have such a hard coat that they can lie dormant through years of drought and sprout only when rainfall returns. Early settlers called the bluebonnets "buffalo clover," and in fact, they are related to the clovers. Like other legumes, they take nitrogen from the air and fix it in the soil. So this Texas wildflower enriches the land even while cloaking it in beauty.

Blue cohosh

Caulophyllum thalictroides

Named for the bluish cast of its foliage, blue cohosh is a deceptive plant: what appears to be three separate leaves is actually a single, very complex compound leaf attached to the main stem. And the clusters of blue berries borne by the three- to four-foot-tall wildflowers are not really berries at all, but seeds. Each greenishyellow flower produces exactly two, which swell to burst free from the enveloping fruit by midsummer. At one time the blue cohosh's root was used by Indian women. Taken as a tea, this "papoose root" helped to hasten childbirth.

Bluefish

Pomatomus saltatrix

Prized by commercial fishermen as popular tablefare and by anglers as game, bluefish are formidable ocean predators that grow up to four feet long and weigh as much as 20 pounds. The blue-backed, silvery-sided carnivores travel in large schools and swiftly track down and attack other schooling fish such as menhaden, mackerel, herring, and even smaller bluefish. Bluefish are found off the Atlantic coast, where they travel toward Florida in winter and north again in summer, following the movements of their favorite prey. Slicing easily through flesh with their razor-sharp teeth, these frantic feeders often eat until full and then continue the slaughter, leaving a floating trail of blood and fish parts in their wake. On forays inshore, they have been known to nip bathers caught amid their prey. The young, sometimes called tailors or snappers, begin life in estuaries and bays. Forming schools at an early age, they soon begin to hone their predatory skills on shrimp, anchovies, and other small prey.

Blue moon

A genuine rarity in the night sky, a blue moon occurs only when smoke and dust particles form a layer in the air. The dusty air screens out all colors except blue from sunlight. And since moonlight is actually reflected sunlight, the moon at such times takes on a bluish cast.

Boa

Compared to their awesome tropical relatives, North America's two native boas are small, rather mild-mannered snakes. Like all constrictors, however, they coil tightly around their prey until it suffocates, then swallow the victim whole. The 18-inch rubber boa of the Far West looks and feels like rubber. It is also called the two headed snake because its blunt tail looks much like its head; when threatened, it rolls up in a ball and, hiding its head inside, lifts its tail toward its attacker. The three-foot rosy boa, with brown to reddish stripes, lives in deserts of the Southwest. Both snakes feed on rodents but also climb small trees in search of nesting birds.

Bobcat

Felis rufus

The most widespread of our wildcats, bobcats are at home in a broad range of habitats; these versatile hunters are found from western chaparral and deserts to eastern forests and southern swamps. In general appearance they resemble tawny, oversized tabby cats with prominent, tufted ears. The "bob" in their name refers to their short tails, a feature shared with their close relative the 1ynx. Masters of the slow stalk, bobcats can also playa waiting game, crouching motionless before pouncing on prey. Scavengers in lean times, they much prefer fresh red meat. Cottontail rabbits are a favorite prey, supplemented by squirrels and mice. At about 20 pounds, bobcats are small compared to mountain lions; even so, they can kill deer many times their size.

Adult bobcats are solitary and seldom meet except to mate, which is done with much loud caterwauling. Reared in dens in rocky crevices, caves, or hollow trees, even as kittens they display the instincts of hunters.

Bobolink

Dolichonyx oryzivorus

In their flight south for the winter, bobolinks travel from the northern United States and Canada all the way to Argentina, a marathon of some 5,000 miles. Their flight note-a metallic sounding pink-can be heard by night as the migrant flocks pass overhead. In the past, hordes of southbound bobolinks descended on the once abundant rice fields of the Carolinas, where the so-called ricebirds were slaughtered as pests. In the summer, bobolinks settle in open grasslands, where they feed on insects and seeds. The males, black except for a tawny nape and white on the wings and back, court their mates with a delightful bubbling song as they flutter through the air.

Bobwhite

See Quail.

Body whorl

The last whorl of the spire of a snail.

Bog

Often thought of as bleak and even threatening places, bogs are actually rich and highly specialized environments. In North America, most bogs are relics of the last Ice Age. As the glaciers retreated, they left chunks of ice buried in rocky debris; when the ice melted, steep-sided ponds were formed and later filled by rain and snow. Too poor in oxygen and nutrients to support most kinds of life, these pockets of moisture offer ideal havens for sphagnum moss. This primitive plant needs no soil, only water, to thrive, and once established, it forms a floating mat that gradually spreads across the surface of the pond. As the mat slowly thickens, it deposits a substantial layer of dead, compressed organic material-peat-on the bottom of the pond.

Because both peat and sphagnum are acidic, bogs can support only acid-tolerant plants. Larch, black spruce, and white cedar typically take root in the moss around the bog's margin; cranberries, bog rosemary, and labrador tea spring up on the floating sphagnum mat itself; and water lilies hold sway in the open water at the center. Many plants that cannot compete on dry land find a haven in bogs, which are excellent places to hunt for the rare lady slippers and white-fringed orchids. And carnivorous plants, which live on insects, thrive on the sphagnum mat. Few fish can survive in the oxygen-poor waters, but frogs, ducks, moose, wolves, and lynx all take refuge in the remote fastness of bogs.

Bonefish

Albula vulpes

Up to three feet long with deeply forked tails, slender, silvery bonefish are found along both the Atlantic and Pacific coasts. They can often be seen as they probe shallows near the shore, nudging the sandy bottom with their snouts in search of shellfish, worms, and other food. Bonefish are a great favorite with anglers because of the vigorous fight they wage on the hook. But after losing the tug-of-war, they usually are tossed back alive, since their flesh is filled with so many bones.

Boneset

Eupatorium perfoliatum

Tall, robust, and crowned with fuzzy, flattopped flower heads, boneset is a familiar sight in the East when it blooms, from late summer into autumn. A white-flowered herb that favors damp meadows, it was recommended by pioneer herbalists for the treatment of fevers and similar ailments. Feverwort, ague-weed, and sweating plant-other old names for boneset- all testify to its medicinal reputation. Even the name boneset refers not to its virtues in healing broken bones, but in curing "breakbone fever," a type of influenza. As recently as 1900, country people still used the plant as a cough and cold remedy, and every farm had a bunch of bone set hanging up to dry in the attic or woodshed.

Borage

Borago officinalis

Ever since ancient times, it has been claimed that this sprawling annual herb could drive away sadness and make men merry. And almost certainly it did when taken as traditionally recommended - in a tankard of wine. Though hairy, the young leaves are rich in vitamin C and, with their cucumberlike flavor, make a tasty addition to salads. Bees are attracted to the plant's flowers-five-pointed stars of blue or purple that produce a generous supply of nectar.

Boundary

The edge between different habitat types. If distinctive, a boundary can be considered a separate edge habitat or ecotone. Boundaries that are readily crossed by an organism are called permeable, those that are crossed reluctantly are called semipermeable, and those that are not crossed are called impermeable.

Bowfin

Amia calva

Often called living fossils, bowfins are the sole survivors of a once widespread family of prehistoric fish. And they demonstrate their survival skills even today: by gulping air at the surface, bowfins thrive in sluggish, oxygen-poor water that few other fish can tolerate. Up to 30 inches long, they are mottled green with a dark spot near the tail and a long fin down the back. Also known as dogfish, grindles, and mudfish, bowfins are found in quiet, plant-choked lakes and streams across most of eastern North America.

Boxfish

A built-in suit of armor-bony plates fused into a protective case-gives boxfish their name. Also called trunkfish, these chunky residents of temperate and tropical seas move about sluggishly, propelled by fins and tail that poke through openings in the rigid case. Boxfish are easily approached by divers as they putter around seagrass beds and coral reefs. Some, such as the smooth trunkfish of the Atlantic coast, use a water-pistol technique to feed: they shoot a stream of water from the mouth, aiming it at the sandy bottom to dislodge small worms and crustaceans that might otherwise remain hidden. Certain species contain a toxin that, if released in an aquarium, can kill every other animal in the tank. Indeed, the boxfish itself sometimes succumbs to its own poison.

Box turtle

Terrapene

When box turtles sense danger, they not only retract their head, legs, and feet like other turtles, but close up their shells as well. A hinge divides the underside into two halves that can be folded up against the rim of the upper shell, sealing the creature in so snugly that not even a knife blade can be inserted between the shells.

Found only in North America, box turtles are five to eight inches long, with yellow or orange markings on their dark backs. They are more at home on land than in water, with the eastern box turtle living in woodlands and meadows and its western cousin preferring the prairies of the south central states. Active by day, box turtles cool off on hot afternoons by soaking in puddles or resting in mounds of damp leaves. In winter, these expert diggers can hibernate as deep as four feet below the ground. If removed from their home territories, box turtles can find their way back using the sun as a navigational aid. But if left alone, they spend their entire lives on just a few acres. And their lives are long indeed; box turtles have been known to survive for more than a century.

Brachiopod

Known mainly by their fossil remains, brachiopods flourished hundreds of millions of years ago when much of North America was covered by shallow seas. Some 30,000 fossil species have been found in sedimentary rocks throughout the country, and a few kinds still survive today. Encased in two saucerlike shells, brachiopods are also called lamp shells because of their fancied resemblance to ancient Roman lamps. Most species live attached to the sea floor by an upright fleshy stalk, relying on movement of the water to bring them food.

Bract

A small leaflike or scalelike structure beneath a flower.

Braided stream

Networks of interlaced channels that repeatedly divide and then rejoin each other, braided streams create striking patterns of land and water. They tend to form where wide, shallow, slow-moving rivers become choked with sediment, forcing the water to find new paths as constantly shifting sandbars block the channel. Melting glaciers, which release huge amounts of eroded debris, frequently produce intricate braided streams, with rivulets of meltwater weaving across one another. Farther downstream, if the slope becomes steeper, the numerous diverging smaller streams often reunite into a single main channel.

Breccia

Formed of coarse, angular rock fragments that have been naturally cemented together, breccias resemble gravelly, manmade concrete. Although they can be produced by any geologic process that breaks up existing rocks, they most commonly result when rock debris- from a landslide, for instance-is dumped in a valley and buried beneath additional layers of sediment. Eventually the rock fragments are compacted and cemented together as smaller grains fill the gaps between them. The very similar sedimentary rocks called conglomerates are made up of pebbles that have been rounded and worn through long transport by streams, rather than the sharp, angular fragments found in breccias.

Breeding Bird Atlas

Bird Biology Avian Conservation term.

See Atlas.

Breeding Bird Census (BBC)

Bird Biology Avian Conservation term.

A census program in North America that uses the spot-mapping method during the breeding season.

Breeding Bird Survey (BBS)

Bird Biology Avian Conservation term.

A cooperative program of the U.S. Fish and Wildlife Service and the Canadian Wildlife Service for monitoring population changes in North American breeding birds by using point counts along roads.

Breeding dispersal

Movement of individuals that have reproduced between successive breeding sites.

Brittle star

With five spiny arms radiating from a small central body, brittle stars resemble their relatives the sea stars, or starfish. Unlike sea stars, however, brittle stars have arms that are long, thin, and flexible, with a snakelike appearance that has prompted their alternate name, serpent stars. The arms are used for moving across the sea floor and for passing food to the mouth, which is located on the underside of the inch wide central body. If an arm is grasped, the creature escapes by allowing it to snap off; hence the name brittle star. Later a new arm grows in place of the lost one. Congregating by the thousands on the deep ocean floor, brittle stars also live in shallower waters along the Atlantic, Pacific, and Gulf coasts. Since they prefer to stay hidden under rocks, in seaweed, or buried in sand, these retiring little invertebrates are seldom seen.

Broad-leaved trees

Oak, beech, ash, hickory, maple-these and other broad-leaved species are the trees that dominate our temperate forests. The secret of their success is the efficiency of their foliage, for leaves are factories that use energy from the sun to manufacture sugars. And since the typical broad-leaved tree boasts four times the leaf surface of a comparable needle-leaved tree such as a pine, the broad-leaved tree is a much more effective solar collector. In addition, most broadleaved trees are deciduous- that is, in contrast to the evergreen conifers; they shed their leaves each fall. This not only protects them from winter cold but also keeps them from drying out, since moisture is easily lost from the broad leaves. The two classes of trees also differ in their methods of reproduction. Broad-leaved trees are flowering plants that enclose their seeds in fruits, while the needle-leaved trees bear their seeds naked and unprotected in cones.

Bromeliad

Spanish moss drooping from the branches of a live oak in the Deep South may not seem to have much in common with pineapples on the greengrocer's shelf. Yet both are members of the same strange plant family-the bromeliads. Some 15 species of these tropical and subtropical plants are native to the continental United States, where they range from coastal Virginia south to Florida and west to Texas. Most of our bromeliads, like Spanish moss, are epiphytes, plants that cling to the branches of trees and shrubs. Their roots never touch the ground, but instead serve mainly to attach the plant to its host. Unlike the dangling threads of Spanish moss, most of our native bromeliads form rosettes of stiff, upright leaves with cuplike bases that collect water. And in contrast to the minute flowers of Spanish moss, most bear conspicuous, brightly colored flower stalks. Not all bromeliads are tree dwellers. Some make their homes more conventionally on the ground-the pineapple, though originally native to Brazil, grows so well in Hawaii's volcanic soils that it has escaped from plantations and run wild through the Kona region.

Brood parasitism

An Animal Behavior term, this means the system in which the young are raised by individuals that are not their parents. Usually, as in the Brown-headed cowbird or European cuckoo, the hosts are of a different species and all young of the parasite species are raised in this way. Brood parasitism may also occur within a species, some females laying eggs in the nests of others.

Brood parasitism (interspecific)

Bird Biology Avian Conservation term.

The laying of eggs by an individual of one species in nests of other species with subsequent care for the parasite young provided by the hosts.

Brown creeper

Certhia americana

Camouflaged by its barklike, streaked, and spotted plumage, the brown creeper is a small and inconspicuous bird that spirals up tree trunks in search of food. Held in place by sharp claws and a stiff, proplike tail, it uses its slender, curved bill to probe for insects and spiders hidden in crevices in the bark. The brown creeper usually begins foraging at the foot of a tree, works its way up the trunk, and then swoops down to the base of the next tree. When alarmed, it spreads its wings and flattens its body against the tree, making itself almost invisible. Brown creepers depend on bark not only for food and concealment, but for their homes as well. Nests are occasionally built in cavities but most often are hidden behind loose strips of bark. Although their usual call is a single lisping note, in the nesting season brown creepers deliver a melodic song more like that of a warbler.

Bryozoan

Commonly known as moss animals because of the plantlike appearance of many species, bryozoans are tiny invertebrates that live in colonies encrusting rocks, shells, boat bottoms, and other surfaces in both salt and fresh water. Each member is encased in a protective capsule, hard in many species but jellylike in others, and each case has an opening through which the animal extends its tentacles to capture food. The colonies assume a variety of forms. Some resemble seaweed fronds and become dry and brittle when washed up on shore; others grow in bushy tufts on coastal rocks. One freshwater species forms spongelike mats; another lives in colonies that look like strings of snail eggs.

Bovids

The common term for the family of Animals named Bovidae, which includes hoofed Animals that have horns which are never shed and are not branched. Horns are present on both sexes. This group includes the Wildlife species bighorn and thinhorn sheep and mountain goat, and the domestic species cattle, sheep and goats.

Browser

An Animal that feeds on leaves, twigs or shoots.

Brow tine

Projection on an antler.

Bryozoan

Commonly known as moss animals because of the plantlike appearance of many species, bryozoans are tiny invertebrates that live in colonies encrusting rocks, shells, boat bottoms, and other surfaces in both salt and fresh water. Each member is encased in a protective capsule, hard in many species but jellylike in others, and each case has an opening through which the animal extends its tentacles to capture food. The colonies assume a variety of forms. Some resemble seaweed fronds and become dry and brittle when washed up on shore; others grow in bushy tufts on coastal rocks. One freshwater species forms spongelike mats; another lives in colonies that look like strings of snail eggs.

Buckeye

Aesculus

Ohio claims one species of buckeye as its symbol, but in fact these American relatives of the imported horse chestnut range east to Pennsylvania, south to Florida, and west to Texas, with a California representative as well. One of the great beauties of late spring, buckeyes bear upright clusters of white, yellow, cream, or even pink flowers. The blooms are followed by thickhulled burs that split in early summer to disgorge large, fleshy seeds with coats like polished mahogany. These may look like chestnuts, but they are bitter to the taste and poisonous. Resourceful Indians, however, still managed to get a meal from the buckeyes by pulverizing the seeds and leaching out the poison.

Buffalo

See Bison.

Buffalo grass

Buchloe dactyloides

Only two to six inches tall, buffalo grass forms a fine, dense, gray-green turf that spreads across portions of the Great Plains like a natural lawn. Indeed, it once covered such vast expanses from Minnesota to Montana and south to Texas and New Mexico that the whole region was known as the short grass prairie.

As the name suggests, buffalo grass was a favorite food of our native bison and furnished herds of millions with nourishing winter forage. The grass was nearly as important to the pioneers who went west to tame the plains. They used blocks of the thick, durable turf to build their snug sod houses. Virtually immune to insects and disease, buffalo grass tolerates extremes of temperature and needs little water. For these reasons it is winning new popularity in the plains states as a lowmaintenance lawn.

Bug

While all insects are commonly referred to as bugs, the term actually applies to just one group-the true bugs. More than 40,000 species of these insects are found worldwide, with some 4,500 of them living in North America. They range from tiny bedbugs to the giant water bugs, aquatic insects that sometimes are more than two inches long. A few characteristics distinguish the true bugs from other insects. Almost all have two pairs of wings. The forewings are thick and leathery near the base and thin and membranous near the tip; the hind wings, used for flying, are completely membranous. Unlike the many insects that bite and chew, bugs have beaklike mouthparts, which they use to pierce the skin of plants or animals and then suck out the juices. In addition, bugs undergo an incomplete metamorphosis. The young, called nymphs, molt several times and develop into adults without passing through a pupal or resting stage-quite different from the complete metamorphosis of beetles.

Bulb

A fleshy, underground structure found in certain plants and comprising leaf bases and next year's bud.

Bulbil

A small, bulblike structure.

Bulk Water Removal (Water)

The removal and transfer of water out of its basin of origin by human-made diversions (e.g., canals), tanker ships or trucks, and pipelines. Such removals have the potential, directly or cumulatively, to harm the health of a drainage basin.

Bullfrog

Rana catesbeiana

Named for their loud, deep-throated croaks, bullfrogs live in the shallows of permanent bodies of fresh water across most of the continent. Up to eight inches long with smooth, greenish brown backs, tan bellies, and powerful hind legs, they are our largest frogs. On spring nights, males shatter the stillness with their booming mating call, a resounding jug-a-rum. While the notes may be jarring to human ears, they attract female bullfrogs in large numbers. After mating, the females lay clusters of as many as 20,000 eggs and attach them to underwater vegetation. The eggs hatch into tadpoles, which, depending on the climate, take one to three years to develop into adults. Hunting mostly by night, bullfrogs prey on insects and other small animals. They can be caught quite easily if dazzled by the beam of a flashlight, and will often "play dead," only to spring back to life and escape at the first opportunity. Many are captured in the wild and raised commercially both for their tasty leg meat and for use as laboratory animals.

Bullhead

See Catfish.

Bullsnake Pituophis melanoleucus

At five to nine feet in length, bullsnakes are among the largest snakes in North America. Their massive bodies are yellow or tannish, marked with dark blotches. Though harmless to man, they can make a tremendous fuss when disturbed, vibrating their tails like rattlesnakes and hissing loudly. Larger specimens even make snorting sounds like those of a bull-hence their name. Powerful constrictors, bullsnakes feed mainly on gophers, rats, and mice and so are protected by farmers in both barn and field. Known in the West as gopher snakes, they are called pine snakes in the East.

Bunting

A number of small, plump, finchlike birds with stout, seed-crushing bills are known as buntings. Some, related to cardinals and grosbeaks, are brilliantly colored. The others, more closely akin to sparrows, wear more somber hues. The brightly tinted buntings are birds of brushy areas. The females, tan or greenish, build their nests well hidden in thickets, while the males flaunt their colors as they sing from conspicuous perches. The male indigo bunting, a rich metallic blue, is one of the few birds that fill the air with song at midday; it performs its recitals well into August. Another, the lazuli bunting, is bright turquoise with orange on the breast. But the most brilliant of all-some call it our most beautiful bird-is the painted bunting. A dazzling patchwork of red, blue, and green, the painted bunting used to be called the nonpareil- French for "unequaled." The drabber buntings prefer open country and nest on the ground. The well-named snow buntings, mainly white with dramatic black accents, winter in the northern states and move about in flocks. In spring they head north for the arctic tundra, where males help the females rear their young. Males of the lark buntings, in stark contrast to snow buntings, are almost completely black, except for a large white patch on each wing. Birds of the Great Plains, they gather in enormous flocks in winter, roaming about in search of seeds.

Burdock

Arctium

Coarse, invasive weeds up to eight feet tall with large, rhubarb like leaves and clusters of purplish, thistle like flowers, burdocks thrive in fields and pastures across much of North America. Two factors have guaranteed their spread despite all efforts to eradicate them: the vigor with which they thrust their thick taproots into the earth (even through compacted, uncultivated soil), and their finesse as hitchhikers. Each bur of 10 to 25 seeds is surrounded by a stubble of tiny hooks that cling tenaciously to any passerby. Tangled in the fur of animals, the seed heads may ride for weeks and miles before dropping off to colonize new territory-and so ensure the burdocks' success.

Bur reed

Sparganium

Well-known to both bird watchers and duck hunters, these freshwater marsh plants are much favored by migratory waterfowl. The long, ribbonlike leaves of the bur reeds, which may rise shoulder high above the water, furnish ducks and other animals with cover in which to hide and nest, while the tough, spiky seed balls serve as an important food source. The plants, in turn, are benefited by the birds; migrating ducks sow the partially digested seeds of bur reeds at stops all along their route.

Burying beetle

Nicrophorus

The undertakers of the insect world, burying beetles specialize in the interment of dead mice, voles, birds, and other small animals. Usually less than an inch long, these glossy black insects with orange-red markings first locate a dead animal with their sense of smell. A mating pair then teams up to push it to soft ground, where the beetles burrow beneath the carcass until it sinks a few inches below the surface. After the pair has covered the body with soil, the female lays eggs on the corpse, which becomes both larder and nursery for the offspring. Burying beetles are also called sexton beetles, recalling the fact that in the past the duties of church sextons included the digging of graves.

Bushtit

Psaltriparus minimus

Tiny, grayish birds with stubby bills and long tails, bushtits spend most of the year in flocks of 20 or more birds, traveling through brushy woodlands in the West. Twittering, acrobatic fliers, the birds call constantly to one another with soft lisping notes as they dart among small trees and shrubs foraging for insects.

Their nest, built over a period of weeks, is a hanging, baglike structure made of twigs, moss, and lichens and held together with spiderwebs. Both members of a pair build the nest, incubate the eggs, and tend the young. Bushtits often raise more than one brood per year, with the young from the previous clutch remaining to help with the new arrivals.

Buteo

Well-equipped for hours of soaring, buteos are hawks with broad, rounded wings and fanshaped tails. Their effortless flight lets them scan vast areas of countryside for prey and migrate for long distances by riding on rising currents of warm air. Found throughout North America, many of the buteos-such as the red-tailed, the rough-legged, and Swainson's hawks-prefer open country, while the broad-winged and the red-shouldered hawks frequent wooded areas.

Butte

Flat-topped and steep-sided, the towering red sandstone buttes of Monument Valley on the Utah-Arizona border are familiar to many as the scenery in western films. One tall, slender butte known as the Totem Pole has the same dimensions as the Washington Monument; at sunset it casts a shadow that extends for miles across the desert floor. Nearby are two massive stumps called the Elephant's Feet, which look like the fossil remains of some ancient behemoth. The buttes are the lonely remnants of a vanished plateau that once stood high above the present valley floor. Attacked by wind and water for countless centuries, most of the rock has long since been worn away. Only the slender, scattered buttes, protected by erosion-resistant caps, remain standing today.

Butter-and-eggs

Linaria vulgaris

Also known as toadflax, these charming wildflowers look so much like their cultivated cousins, the snapdragons, that admirers sometimes transplant them into their gardens. Up to three feet tall and topped with jaunty spikes of flowers, butter-and-eggs thrives in fields and on roadsides throughout most of North America. Each pale yellow blossom has an orange lobe on its lower lip that both marks and blocks the entrance to its nectar supply. Since the sweet liquor is hidden at the end of a long spur, only long-tongued insects, such as bumblebees, can get at it. After drinking their fill, they emerge from the blossom thoroughly dusted with pollen, ready to fertilize the next plant they visit.

Buttercup

Ranunculus

Shiny yellow five-petaled buttercups are a conspicuous sight throughout the country, adding a bright splash of color wherever they spring up. Also called crowfoot because of the shape of their leaves, these wildflowers are fond of moist areas, and a few kinds even grow in water. One species, the tall buttercup, is a favorite with children, who hold the blossoms under each other's chin in a test that supposedly reveals their fondness for butter. Water crowfoot, which grows underwater, sends up creamy white blossoms that unfold above the surface. Despite their innocent appearance, some buttercups contain an acrid, toxic juice that can cause dizziness and even death in livestock. Fortunately, most grazers eat buttercups only as a last resort. Once having tasted the weeds, however, farm animals sometimes develop a perverse liking for it and return repeatedly for more, even after suffering from its ill effects. The juice of some kinds, while not as dangerous to humans, can blister the skin.

Butterfish

Silvery, schooling ocean fish with high, thin bodies that from the side seem almost round, butterfish look a bit like shiny, oversized silver dollars. (Some, in fact, are known as dollarfish.) Six to 12 inches long, with tiny mouths and deeply forked tails, they live in temperate to tropical waters along the Atlantic and Pacific coasts. Among the more common species are harvestfish, found in Atlantic waters, and the Pacific pompano; both are valued as food fish. Showing a marked tendency to seek shelter beneath floating objects, young butterfish often take up residence under the bells of jellyfish. One, the man-of-war fish, lives relatively unscathed amid the poisonous stinging tentacles of the notorious Portuguese man-of-war. When grown, however, butterfish abandon the protection of their floating, jellylike umbrellas and travel in schools.

Butterfly

Among the most beautiful members of the insect world are the butterflies. Together with moths, they make up the order Lepidoptera, from the Greek lepus, meaning scale, and pteron, meaning wing. The order is well named, for butterflies and moths are distinguished from all other insects by the minute scales that cover their wings. The differences between butterflies and moths are usually conspicuous. Butterflies ordinarily fly by day and are brightly colored, while moths have dull colors and fly by night. Butterflies tend to rest with the wings folded up over their backs, and moths rest with the wings fanned out. There are, however, notable exceptions to these "rules," and the only sure way to recognize a butterfly is by examining its antennae. Butterfly antennae have a knob at the tip; on moths they are feathery or finely pointed. Nearly 700 species of butterflies are found in North America, and they vary widely in shape, color, and ornamentation. Some, such as the skippers, are dull, stocky, and mothlike in appearance. The checkerspots and fritillaries, in contrast, have elaborate, boldly colored wing patterns in orange, yellow, and black. The blues, coppers, and metalmarks not only are colorful but have an iridescent glow. The buckeyes, pearly eyes, and satyrs are ornamented with eyespot patterns- prominent black spots or colored concentric circles on the wings. Other butterflies are known for the unusual shapes of their wings. The anglewings have jagged, irregularly shaped wings. Swallowtails and daggerwings have daggerlike extensions on their hind wings, while the hairstreaks have thinner, more hairlike "tails." The particles of "dust" that rub off the wings of a captured butterfly or moth are actually tiny scales. Arranged like shingles on a roof, they account for the variety of colors and patterns on butterfly wings. In some species the scales are colored by pigments. In others, they are grooved in such a way that the play of light on their surfaces produces the effect of color. The iridescence on the wings of blues and coppers is caused in this way, and their metallic glint is accentuated by a thin film of oil on the scales. Wing scales also playa role in the mating of butterflies, which rely on scent to attract and locate the opposite sex. Glands at the base of some scales produce a distinctive aroma, which is diffused through tufts of very fine hairs at the tips of the scales. As if to confirm his amorous intentions, a male sometimes brushes these hairs over the antennae of the female. The patterns on butterflies' wings play a significant role in their survival. Many have wings that so closely mimic the leaves, twigs, or bark they rest on that they are nearly invisible to predators. Wings with eyespots and other patterns mislead predators, encouraging them to bite in nonvital areas. And bright colors, though conspicuous, often startle would-be predators or deter them in other ways. The brightly colored monarch, for instance, is highly toxic. Once a predator learns this, through trial and error, it will leave the monarch alone. The nontoxic viceroy, nearly identical in appearance to the monarch, survives by capitalizing on mistaken identity. In the course of its life, a butterfly undergoes a complete metamorphosis, drastically changing in form and appearance. The four stages in its life cycle consist of the egg; the caterpillar, or larva; the chrysalis, or pupa; and finally the adult butterfly, or imago.

The adult female lays a few to several hundred sticky eggs: depositing them on the leaves or stems of plants best suited to the food needs of the caterpillars. Some butterflies lay their eggs singly, others in chains or large clusters. The shapes of the eggs, which are best observed with a magnifying glass, vary with the species; some are simple, smooth spheres, while others have unusual shapes and may be elaborately ornamented, with fluted, ribbed, or pitted surfaces. Unless the egg is meant to survive the winter, as in some species, the caterpillar normally hatches within a week and begins gorging on food. During the larval stage the caterpillar must eat as much as it can to sustain it through the noneating pupal stage. To avoid being eaten themselves, many caterpillars are well camouflaged, and those that are not are often conspicuously colored, relying on their unpleasant taste or an armor of spines to make them difficult for predators to swallow. After about a month of eating and several molts to accommodate its increasing size, the caterpillar settles into a suitable spot to pupate. It may hang from a plant by a silken thread, attach itself to a stem with a girdle of silk, or remain on the ground. After a few days the caterpillar's skin shrivels and is cast off, leaving the chrysalis, or pupa. The outside of the chrysalis, though usually blending in with its surroundings, also shows the rudimentary outlines of the developing butterfly's wings, eyes, and legs. Eventually the chrysalis splits open, and the adult insect pulls itself free, climbing onto a twig or leaf to rest while its wings expand and dry. Soon it flies off to begin life as an adult butterfly, a life that will last an average of two weeks but may continue for many months. The adult butterfly survives on plant nectar, which it drinks through its long, tubelike tongue, or proboscis. The nectar provides the energy needed for flight and for the butterfly's last and most important function: reproduction. Once a male and female of the same species have found each other, they begin an aerial courtship that involves elaborately choreographed movements such as fluttering, diving, and spiraling. Mating itself begins on a branch or other perch and may continue in the air. Finally, some days after mating, the female lays her eggs, and the complex and astonishing life cycle of the butterfly begins all over again.

Cabbage butterfly Artogeia rapae Common in fields and gardens across the country, cabbage butterflies are serious agricultural pests whose larvae feed on cabbage, mustard, cauliflower, and other crop plants. Accidentally introduced to North America in the 1860's, they have since become the most common butterfly in many areas; they can even be seen fluttering over the scattered patches of greenery in cities. Not the most colorful of their kind, cabbage butterflies have white forewings tipped with black. Dark spots, one on the male and two on the female, dot the wings near the bottom edge. The caterpillars, which hatch from eggs laid on plant leaves, are bright green with yellow stripes.

Butterflyfish

Like butterflies in a flower garden, these dainty, disc-shaped fish flash with bright colors as they flutter across reefs of rock or coral. Though they prefer shallow tropical seas, a few hardy species venture as far north as New England. Many, like the foureye butterflyfish, have dark bands that mask the eyes and dummy "eyespots" toward the rear of the body; would-be predators mistake tail for head and lunge at the less vulnerable end of the fish. With tiny, pouting mouths lined with bristly teeth, butterflyfish feed on coral polyps, tubeworms, and algae. The longsnout butterflyfish of Florida can insert its slender nose between the spines of sea urchins to extract prey. Other species are living vacuum cleaners, nibbling parasites from the skins of infested fish.

Butterwort

Pinguicula

Lying flat on the ground, the butterworts' rosettes of greenish-yellow leaves glisten in the summer sun. Their sheen results from drops of liquid secreted by glands on the upper surfaces. This sticky secretion gives the leaves a greasy feel; hence the name butterwort. It also serves a vital purpose: it transforms the leaves into a kind of natural flypaper designed to trap any small insects that land on them. The leaves then secrete a digestive juice, extracting nitrogen and other vital nutrients from their prey. Found in bogs and other damp places, the carnivorous butterworts make a lovely display from spring into summer as they wave their colorful, spurred blooms atop delicate stems.

Buttonbush

Cephalanthus occidentalis

Although it is fairly widespread across the country, few people know this handsome shrub, for buttonbush hides in swamps and along the drowned margins of ponds and streams. At summer's end, however, a rich aroma reveals its presence; it is then that the buttonbush bears its creamy, sunburst-shaped, richly fragrant flower heads, which provide a welcome feast of nectar for bees and other insects. The name buttonbush derives from the spherical seed heads, up to an inch across, that follow. Hanging from the barren branches all winter long, they look a bit like buttons dangling from a tattered coat.

Cactus

Characterized by fleshy stems and an armament of spines, the cacti are a richly varied plant family. Of the 2,000 species included in the group, all but 1 are native to the New World, and some 1,200 are indigenous to North America alone. They range from the tiny, buttonlike peyote to the sentinel-like saguaro, which grows up to 60 feet tall. The most notable common characteristics of the cacti are their many adaptations for surviving drought. Their bodies are filled with soft, porous tissue that absorbs water and holds it like a sponge, allowing them to store moisture in wet periods for use through the ensuing dry seasons. Some of the cacti are ribbed with accordion-like pleats that enable them to expand as they fill with water. To minimize the amount of moisture lost by evaporation through the skin, most cacti produce no leaves and have a waxy, waterproof outer covering. Even their shapes - globes, cylinders, and barrels-help guard against dehydration, since they are the forms that allow for the greatest volume with the least surface area. When the rare rain does fall, some of the cacti respond by sending out shallow networks of hairlike roots to tap the moisture, then shed the new growth when the soil dries. The cacti's spines also play a vital role in survival. More than mere protection against grazers, they cast enough shadow to help shade the plants and keep them cool. (The layer of air trapped under the spines may be 20°F cooler than the outside air temperature.) By slowing the circulation of air, the spines also help minimize the drying effect of wind. In some cases, they even function as water collectors; moisture from fog or light rains condenses on downcurved spines, gradually collecting into drops that fall directly on the roots.

Caddisfly

Found in ponds and streams across most of the country, caddisfly larvae are freshwater aquanauts. Those of some species tend silken nets that they spin to entrap food, but many others move about in search of their meals, secure in the protection of mobile homes that they build around their own bodies. The cases are usually tubular, with only the larva's head and legs projecting from one end. Building materials, held together by silk or glue, range from sand grains to plant stalks and pieces of shell. As they approach maturity, the caddisworms seal up their cases and pupate inside. Eventually they are transformed into delicate, winged, mothlike insects of the night.

Caldera

Far different from the small craters found atop volcanic mountains, calderas are huge circular depressions that result when a volcano completely destroys itself. They usually are formed when an extraordinarily violent eruption spews out so much lava that the magma chamber beneath the volcano becomes empty, causing the top of the mountain to collapse into itself. A well-known relic of such an event is Crater Lake in the Cascade Mountains of Oregon. The six mile-wide expanse of water fills a caldera left behind by the titanic explosion of Mt. Mazama, an ancient volcano. Almost 2,000 feet deep, Crater Lake is the deepest in the United States. Only Wizard Island, a small volcano rising above the water's surface, gives a hint of the fiery mountain that once stood where the lake is now.

California poppy

Eschscholzia californica

In late April, when the hillsides of southern California blaze with countless millions of these golden blossoms, it is easy to understand why early explorers sometimes called the area "the land of fire." Borne one to a stem atop mounds of finely cut, blue-gray foliage, the cup-shaped flowers of the California poppy usually have four petals and range in color from brilliant yellow to deep orange. The elongated pods that follow the bloom explode when they mature, scattering seeds for several feet. The official flower of California, this delightful native poppy is at its best there. But it is widely cultivated as a garden flower as well and has established itself in the wild as far afield as Australia.

Camas

Camassia

Before the arrival of white settlers in the West, these showy members of the lily family were so plentiful that their starchy bulbs were a staple food of several Indian tribes. Five species of camas flourished in damp meadows throughout much of the West, with one, the wild hyacinth, found as far East as Pennsylvania. Explorers described vast expanses of starry blue, white, and purple blossoms clustered atop wandlike stems that rose two to three feet from tufts of grassy leaves. Nowadays the common camas, or quamash, sometimes still colors whole meadows, but the other camases have been wiped out in many areas, the result of overgrazing and cultivation of the land.

Camouflage

Whether hunters or hunted, many animals make use of camouflage to escape enemies or deceive prey. In most cases they rely on color or pattern to blend into their surroundings, but shape and posture can also play a role. The green snakes, for instance, all but disappear as they slither through the grass, and the mottled brown woodcock is nearly invisible on the forest floor. Fawns, brown and spotted, are inconspicuous in sun-dappled woodlands, while on open beaches plover chicks, as well as the eggs from which they hatch, are colored like the sand and pebbles around them. Another form of deception, called countershading, is practiced by animals with dark backs and light undersides. When seen from above, the dark backs of fish such as bass and mackerel blend in with the dark water; when seen from below, their light bellies are indistinguishable from the sunlit surface. Many birds with dark backs and white breasts wear a similar disguise. Other animals actually change color to match their surroundings. Flounders and the chameleon-like anoles, for example, change to blend with their backgrounds when they move from one place to another. Ptarmigans, ermines, and snowshoe hares, in contrast, change color with the seasons. During the summer they wear dark, earth-colored feathers or fur. But in winter, their warm-weather colors are replaced by suits as white as snow. In the insect world, many grasshoppers, katydids, mantids, and others are as green as the plants they rest on, and moths and caterpillars often are patterned like dead leaves, bark, or other vegetation. But the real professionals in the camouflage act are the ones that pose as inedible objects. Walkingstick insects are easily mistaken for twigs, and many of the treehoppers look exactly like thorns.

Camouflaged

An Animal Behavior term, this is used to describe color and patterns of Animals which blend with their background, thereby minimizing the risk of predation or, in the case of predators, enabling undetected approach to prey.

Campion

Lychnis

Hardy members of the carnation family, campions are most commonly found in cool northern regions. The white campion, however, ranges as far south as South Carolina. Opening only at night, its inch-wide blossoms are white, making them more visible to the moths on which they depend for pollination. Its day-blooming relatives, such as red campion and ragged-robin, have more-colorful flowers in shades of red and pink. The name campion is also applied to a number of catchflies, similar wildflowers that belong to another genus.

Endangered and Threatened species term.

Plants and animals that have been studied and the U.S. Fish & Wildlife Service has concluded that they should be proposed for addition to the Federal endangered and threatened species list. These species have formerly been referred to as category 1 candidate species. From the February 28, 1996 Federal Register, page 7597: "those species for which the Service has on file sufficient information on biological vulnerability and threat(s) to support issuance of a proposed rule to list but issuance of the proposed rule is precluded."

- A term no longer in use, having been replaced by the term "candidate species" which uses the same definition.

- A term no longer in use. Previously referred to species for which the Service had some indication that listing as threatened or endangered might be warranted, but there were insufficient data available to justify a proposal to list them.

- A term no longer in use. Previously referred to species which once were category 1 or 2 candidate species, but for which subsequent data indicated that listing as threatened or endangered was not appropriate.

Canine

The domestic dog and its wild, meat-eating relatives, such as wolves, coyotes, and foxes, are all canines. Common characteristics of the wild canines are long, pointed snouts, triangular ears, and bushy tails. Lean, muscular, and longlegged, they are good runners, well suited for the pursuit of prey. They also are intelligent animals, with keen senses of hearing and smell.

Cannibalism

An Animal Behavior term, this describe eating members of an Animal's own species. It has been reported in many species but is relatively uncommon, except in Animals subjected to stress or high population density.

Canyon

A mile deep in places, the Grand Canyon in northern Arizona covers an area the size of Delaware. From the rim, the river that created the awesome abyss can barely be seen. Snaking across the bottom of the gorge, however, the Colorado River continues to slice downward through the rock. Its power to erode is evident in the river's muddy water, which has been carrying away tons of silt, sand, and gravel for some 20 million years. The river was not the only agent involved in deepening the canyon, however. At the same time that it was cutting downward, upheavals of the earth's crust were raising the Colorado Plateau through which the river had to carve its pathway to the ocean. In the process, layers of rock representing a billion years of geologic time have been exposed. The stepped appearance of the canyon walls results from the fact that the different kinds of rock vary in their ability to withstand erosion. Although the many canyons carved into the brightly colored rocks of the Colorado Plateau are among the most beautiful, canyons are common throughout the West. They occur in arid regions where rivers deepen gorges faster than their steep sides can be reduced by weathering.

Cap

A structure seen in fungi under which spore-bearing structures, usually gills or pores, are suspended. The top of a mushroom.

Capsule

A structure within which seeds are formed in flowering plants and spores develop in mosses and liverworts.

Capture-recapture method

A procedure involving the distinctive marking of individuals and their subsequent recapture (or sighting) to estimate population size and other population parameters.

Caracara

Polyborus plancus

Large, dark, long-legged, and long-necked, with a distinctive black crown and red, naked face, the crested caracara looks and behaves somewhat like a vulture, although in fact it is related to the falcons. It gets its name from its harsh, cackling cry and makes its home on open scrublands in Florida, coastal Texas, and southern Arizona and New Mexico. In flight this splendid bird can be identified by its long, broad wings with conspicuous white patches. It is more commonly seen on the ground, however, walking in a regal manner or feeding, alongside vultures, on carrion. A brash bully that is not above stealing food from vultures, the caracara also captures frogs, lizards, and other small prey.

Carapace

The hard, upper surface of a crustacean's shell. Protecting the bodies of creatures as diverse as crabs, insects, and turtles, an animal's carapace is a rigid case covering all or part of its back. On turtles, the carapace is the domed upper shell and is composed of a bony layer overlain by hard, horny plates. The carapace of insects and crustaceans, such as crabs and shrimp, is made of a tough, waterproof substance known as chitin. As with turtles, this enveloping armor protects the animals from predators and prevents moisture loss. But it has another function as well: whereas turtles have an internal skeleton of bones, the carapace of insects and crustaceans serves as part of their external skeleton.

Cardinal

Cardinalis cardinalis

Bright crimson plumage and a regal crest make the northern cardinal unique and unmistakable. Its stout, cone-shaped bill identifies the bird as a seedeater, and indeed the cardinal is a familiar sight at feeders everywhere east of the Great Plains as well as in parts of the Southwest. Originally confined to the southern states, the nonmigratory cardinal is gradually expanding its range northward into Canada. Aggressively territorial, cardinals sing with a variety of loud, clear whistles. Females, though more subdued in color than the males, have the same distinctive crest and are just as vocal. Nesting in shrubs and thickets, the birds often raise more than one brood a year, with the male caring for the young while the female begins the next brood.

The pyrrhuloxia, a close relative of the northern cardinal, lives in desert scrub in the Southwest. Also known as the Texas cardinal and the parrot-bill, it is mostly gray, with a few prominent patches of red, but nevertheless looks much like its more brightly colored cousin. Both the male and female share in building a tidy, cup-shaped nest in thorny desert scrub, where they raise just one brood each year.

Cardinalfish

Found near coral reefs in warm or tropical seas, most cardinalfish, true to their name, are vivid red. Despite their bright color, however, the tiny fish - most are just one to four inches long - are often difficult to spot. During the day they elude predators by hiding in crevices, caves, burrows, and even in or on other animals. Some species, for instance, dwell among the spines of sea urchins, the tentacles of sea anemones, and between the valves of certain clams. Brownish rather than red, the sponge cardinalfish lives in tube sponges, while the conchfish inhabits the snaillike shell of queen conchs. At night, the cardinalfish emerge from their hiding places and hunt for small prey.

Caribou

Rangifer tarandus

Like their old-world relatives, the reindeer, caribou are stocky deer of the Far North, with the biggest males weighing as much as 700 pounds. In contrast to most other deer, both sexes have many-branched antlers, though the males' are much larger. Big round hooves ease their passage as they roam across bogs, snow, and soggy tundra. The hollow outer hairs of their coats keep them warm and help make them buoyant (caribou are excellent swimmers), while dense underfur insulates them. Two races of caribou are found in North America. Woodland caribou live year-round in northern evergreen forests across much of Canada. Barren ground caribou, on the other hand, are migratory and travel in herds that sometimes number in the tens of thousands. They winter in forests just south of the tree line and in spring head north for the Arctic tundra, a journey of up to 800 miles. Following the same routes year after year, they feed along the way on grasses, sedges, and the abundant lichens known as reindeer moss. Calves born on the trek follow their mothers when just hours old.

At summer's end, the herds turn south again. Males battle with each other during the autumn mating season, with the winners establishing and jealously guarding harems. The herds then spend the lean winter months in the forest, browsing on willow and dwarf birch and pawing through the snow with their sharp-edged hooves to reach buried lichens.

Carnivore

To the taxonomist, the term carnivore refers to land-dwelling mammals in the large order that includes such diverse creatures as dogs, cats, weasels, and bears. But in a broader sense the word can be applied to any animal - from birds and fish to reptiles and insects-that feeds on other animals. Herbivores, in contrast, are animals that feed mainly on plants, while omnivores eat both plant and animal matter. Carnivores have adapted to capturing and eating food in a variety of ways. Hawks and owls, for instance, are equipped with hooked, flesh-tearing beaks, while the specially hinged jaws of snakes enable them to swallow their prey whole. Other animals, such as cats, rely on agility and speed to outmaneuver their victims.

Carnivorous

A carnivorous creature is any mainly or exclusively meat-eating organism; alternatively. a member of the order Carnivora, many of whose members are carnivores.

Carnivorous plants

More than 40 species of carnivorous plants are native to the United States, and like their hundreds of relatives around the world, they all thrive on adversity. Although they manufacture most of their food in their leaves just as other plants do, their ability to trap and digest insects and similar prey has enabled them to flourish in habitats where few other flowering plants are able to survive. Most carnivorous plants live in bogs or swamps, where the highly acidic soil lacks vital mineral nutrients and so is too poor to support most vegetation. The carnivores are able to flourish in such places because of the extra nitrogen, phosphorus, and trace elements they derive from their animal prey. In general, carnivorous plants are of two kinds: those with active traps and those with passive ones. The best known of the active trappers is the Venus flytrap, which has specially adapted leaves that snap shut like bear traps on unwary insects. Passive traps are used by the pitcher plants, which drown their prey in pools of liquid, and by the sundews and butterworts, which secrete sticky fluid on their leaves, turning them into a kind of natural flypaper. The aquatic bladderworts consume any small animals that are sucked into their bladderlike underwater traps. Because of their unique adaptation to one kind of environment, many carnivorous plants have severely limited ranges. The Venus flytrap, for example, occurs naturally in only one small area of North and South Carolina. On richer soils, few of the carnivores can compete with less specialized but more vigorous plants.

Carp

Cyprinus carpio

Hardy and adaptable fish, carp thrive in almost any freshwater environment, from weed-infested lakes and rivers to polluted ponds and backwaters. Asian natives, they were introduced to North America from Europe, where they are commonly cultivated for food. Many think the introduction was a mistake, however, because carp frequently displace more desirable fish. Since they feed by rooting on the muddy bottom for small animals and plants, they often destroy the eggs of other species, as well as the vegetation that the young fish need for cover. Carp are stout-bodied fish with short, fleshy whiskers near the mouth. Their large, coarse scales are dark on the back and tinged with bronze on the sides. Although they average about 15 inches in the wild, carp raised in captivity may grow to 3 feet and live for 40 years. Some anglers value carp for sport. The fish are normally caught with rod and reel, but when large numbers are found in shallow water, carp are sometimes shot with bow and arrow.

Carpal

Bird Biology Avian Ecology term. The area on a bird's wing corresponding to the "wrist" joint.

Carrying Capacity

The constant number that, left to itself, a natural population will achieve in a given ecosystem. The idea there is a constant number is, according to some ecologists, an unwarranted assumption. See Balance of Nature. The maximum number of individuals that can use a given area of habitat without degrading the habitat and without causing social stresses that result in population reduction.

Caste

An Animal Behavior term, this is used to described individual members of a species which are adapted to perform a particular task, both by their structure and their behavior. Usually applied only to social Insects such as Honeybees and Termites.

Catalpa

Catalpa

Lush and green, with large, heart-shaped leaves throughout the summer, catalpas have an exotic, almost tropical look. But the trees are at their best when covered with big, upright clusters of showy white flowers in late spring and early summer-a time when few other trees are in bloom. Attractive and fast-growing, they have been valued as shade and ornamental trees ever since 19th-century settlers began planting them in parks and gardens. As a result, both of our native species-the northern catalpa, which was once confined to a small area of the Midwest, and the southern catalpa, once found only near the Gulf Coast-now are common in all but the coldest states. The trees also are known as Indian beans because of the long beanlike pods that develop after the flowering season. Turning brown, they hang on the trees all winter long before splitting open and shedding their seeds the following spring. The leaves of the northern species are fed upon by caterpillars of the catalpa sphinx moth. Green and horned, the larvae eventually mature into colorful and convincing mimics of the hummingbird.

Catastrophe

An event that causes sudden decreases of population size or the entire elimination of subpopulations.

Catastrophism

Biological Philosophy term. One side of a nineteenth-century geological argument about the forces that have shaped the earth. Catastrophism proposes that the earth was shaped by sudden, cataclysmic upheavals (such as the "Flood" or "Deluge" of Noah in the Bible) and that the laws of nature in the periods between these cataclysms are not the same, that is, "uniform." The issue is this: if the laws are not uniform, we cannot really see back beyond the last major cataclysm and so cannot reliably talk about millions of years in the past. Compare Uniformitarianism.

Catbird

Oumetella carolinensis

An uncanny, catlike mewing announces the presence of the gray catbird even before the black-capped, slate-gray bird itself emerges from the underbrush where it usually hides. Like its close relative the mockingbird, the catbird is a talented mimic. Its renderings are not as varied or as accurate as the mockingbird's, but its often melodious, sometimes squeaky phrases clearly suggest the songs of other species. Breeding across most of North America from southern Canada to the Gulf States, the catbird is a friendly creature that is welcomed in suburban yards and gardens. Both males and females incubate the four to six shiny, greenish-blue eggs in a cuplike nest of twigs. In spring, the catbird feeds almost exclusively on insects and provides a valuable service by eating the destructive caterpillars of the gypsy moth.

Catchfly

Silene

Widespread members of the pink or carnation family, the catchflies are so called because crawling insects sometimes get caught in the sticky hairs on their stems. Unlike the carnivorous plants, however, the catchflies do not consume insects as food. The stickiness instead serves as a barrier that prevents crawling insects from pilfering the flowers' sweet nectar, which is reserved for the flying insects that distribute pollen. Known by a variety of names, some of the catchflies are called campions because of their resemblance to their near relatives, the true campions, while still others are called pinks.

Caterpillar

A larval stage of a butterfly or moth. The wormlike larvae of butterflies and moths, caterpillars got their name from a word meaning "hairy cat"-and many are hairy indeed. The wooly bear, the larva of the Isabella tiger moth, has a thick coat of black hair with an orange band on its midsection that supposedly predicts the length of winter. Such bristly surfaces discourage predators; some caterpillars further protect themselves by secreting irritants from special glands. Smooth-skinned caterpillars include the inchworm, which moves by alternately hunching and stretching its body, and the striped larva of the monarch butterfly.

Catfish

Whiskerlike feelers, or barbels, around their mouths give the catfish their name. Living on the bottoms of lakes, ponds, and slow-moving streams, they use the taste- and touch-sensitive feelers to help locate their food, which includes fish, insect larvae, crustaceans, and a wide variety of other creatures. Catfish have no scales, but some of their fins are armed with sharp spines that can cause painful injuries. The most abundant of the North American catfish are the bullheads. Popular with anglers, they average 10 inches in length but can grow much bigger. The largest American species, the blue catfish of the Mississippi River system, grows to five feet and weighs as much as I50 pounds. The channel catfish, slender by comparison, reaches four feet but weighs only 30 pounds. Popular as food fish, catfish are raised on commercial fish farms in the South.

Catkin

A flowering structure of certain trees and shrubs. Found on a variety of deciduous trees and shrubs, from willows to oaks and birches, catkins are flower clusters pared down to the bare essentials. On pussy willows they are the small silvery tufts that stand erect like furry candle flames, signaling winter's end; on hickories they dangle like long, fuzzy pendants, each one containing dozens of individual flowers along its length. Because most depend on the wind for pollination, these tiny flowers lack petals and sepals-any structures that might impede air circulation. And most catkins appear in early spring, while the branches are still bare. Often the male (pollen-producing) and female (seedproducing) flowers are borne on separate catkins and sometimes on separate plants.

Cattail

Typha

The tall, sturdy stalks with cigar-shaped tips that give cattails their name are a common sight in marshlands all across the continent. Shooting upward in the spring, they wave the cattail's densely packed flowers aloft where the wind can catch their pollen and carry it far and wide. A single flower head may produce more than 140,000 seeds, each of them equipped with its own parachute of down to help it sail away to new territory. If a seed lands on well-watered soil, it can develop in a single season into a patch of cattails 10 feet across.

Cattails have been used in remarkably varied ways. Indians and pioneers wove the leaves into baskets and chair seats, and cattail fluff once served as stuffing for quilts and mattresses. The pollen makes a tasty flour substitute, and the cooked roots are as nutritious as rice.

Caudal fin

The tail fin of a fish.

Causation

An Animal Behavior term describing the immediate causes of behavior and the mechanisms by which they act. Studies of causation investigate factors such as how external stimuli and internal factors, such as hormones, affect behavior and the neural structures involved in its production.

Cave

Festooned with iciclelike stalactites, rosettes of mineral crystals, and other exotic formations, caves encompass some of North America's most fascinating scenery. Usually found in areas underlain by thick layers of limestone, they are formed when slightly acid water seeps through cracks in the soluble rock and dissolves ever larger openings. Caves sometimes develop into complex systems of rooms and winding passageways, which can be many miles long and extend deep into the earth's interior. Among the best known of these hidden underground worlds is Carlsbad Caverns in New Mexico. Its "Big Room" covers 14 acres and has a ceiling that, at its highest, could accommodate a 30-story building. Once filled with moving water, the chambers at Carlsbad eventually were raised above the water table and now are relatively dry. Kentucky also is riddled with caves. The largest, Mammoth Cave, has miles of interconnecting rooms linked by twisting passageways. With streams still running through its lowest levels, this remarkable cave system continues to grow. Missouri, too, is pitted with hundreds of caverns. One of them, the labyrinthine Mark Twain Cave near Hannibal, was made famous by Twain's novel Tom Sawyer.

Cave animals

Though dark and mysterious, caves nevertheless are home for a rich variety of animal life. Owls roost by day in crevices near the entrances, while phoebes and swallows build mud nests on the walls. Pack rats nest on the floor, venturing outside at night to forage and look for objects to add to their collections of debris. Deeper inside the cave are the permanent residents, including fish, crayfish, salamanders, spiders, and beetles. In their world of perpetual night, high humidity, and nearly constant cool temperatures, these creatures have developed a number of special adaptations. Many fish have lost all pigmentation and are as white as alabaster. Most cave fish are blind as well, with mere traces of eyes, or none at all; highly developed senses of touch, smell, and hearing compensate for their lack of vision. Many of the crayfish, salamanders, millipedes, and other creatures of the cave also are colorless and blind. The best known of all cave dwellers are bats, which roost in the caves by day and emerge at night to feed on insects. The roosting bats often are so numerous that they form a dense canopy across the ceiling. And when they leave at dusk, they come out in huge clouds that darken the sky. Carlsbad Caverns in New Mexico were discovered by a cowboy who spotted a cloud of bats. Bracken Cave in Texas, another notable roost, is home to an estimated 20 million bats.

Cecropia moth

Hyalophora cecropia

Often seen fluttering near bright lights, the cecropia moth is popular with collectors. Its velvety brown wings, with a span of about five inches, are brightly patterned with white and reddish bands and spots. The adults do not eat, but the larvae-green, with spiny red, yellow, and bluish tubercles-feast on the leaves of many trees and shrubs. Found in cities, suburbs, and rural areas, cecropia moths range from the Atlantic Coast to the Great Plains.

Cedar

The coniferous evergreen that the ancient Greeks called kedros was made famous by King Solomon, who used its timber for the temple at Jerusalem. He chose the cedar for its reddish, aromatic, rot-resistant lumber. While the true cedars are old-world species, a number of our native evergreen trees have similar wood and were dubbed cedars by the early settlers. This has resulted in a great deal of botanical confusion. The eastern red cedar and southern red cedar, for example, are actually junipers, and the western red cedar, also known as giant arborvitae, is really a thuja. The Atlantic white cedar belongs to yet another genus. Adding to the confusion, a rare tree native to Florida, a relative of the yews, is called stinking cedar because its leaves release a fetid odor when bruised. This use of the word cedar for so many conifers illustrates how misleading common plant names can be. For although all our cedars are evergreens with durable, aromatic wood, none are closely related to Solomon's tree.

Celandine

Chelidonium majus

One of the earliest spring wildflowers in the northeast, celandine unfurls its bright green, deeply cleft foliage before the last snow melts, and opens its small, four-petaled yellow flowers by late April or early May. Farther south the plant is virtually evergreen, especially when it grows in a sheltered spot at the foot of a sundrenched wall. A member of the poppy family, celandine has orange sap that oozes from any cut stems. And as with many of the poppies, the sap has been used medicinally, though in this case to clear the eyes, not cloud the senses.

Census (noun)

Bird Biology Avian Conservation term.

A count of all individuals in a specified area over a specified time interval.

Census (verb)

Bird Biology Avian Conservation term.

The act or process of counting all individuals within a specified area and estimating density or a total population for that area.

Census efficiency

Bird Biology Avian Conservation term.

Proportion of actual population density that is assessed by a census.

Centipede

Unlike some of their tropical relatives, which can be as much as a foot long, our centipedes are rarely more than an inch in length. Even so, they are agile predators that run down insects, spiders, and earthworms. Though their name suggests that centipedes have 100 legs, the actual number varies from fewer than 40 to more than 340. One pair of legs is located on each body segment; they walk by moving the legs in neatly coordinated, rhythmical waves. Centipedes hide in dark, damp places under rocks, logs, and in leaf litter during the day and come out at night to hunt. They use their long, sensitive antennae to locate prey, and then paralyze it with their poison claws. Although most species are harmless to humans, some of the larger southern centipedes can inflict painful bites.

Century plant

See Agave.

Cephalopod

Squid, cuttlefish, octopuses, and the nautiluses all are cephalopods. Their name, from the Greek for "head-feet," refers to the fact that their grasping armlike tentacles grow out from the head. Like clams and snails, cephalopods are mollusks, but only the nautiluses have external shells. Cuttlefish and squid have only rudimentary shells imbedded in their bodies, and the octopuses have no shells at all. Among the most extraordinary features of the cephalopods are their "camera" eyes, with lenses that can be focused, like human eyes-an asset in capturing prey. Highly mobile, the cephalopods are jet propelled, moving about by expelling water through a muscular siphon in their bodies.

Cephalothorax

The fused head and thorax found in spiders.

Cerci

The paired appendages at the hind end of an insect's body.

Cervid

The common term for the family of Animals named Cervidae, which includes hoofed Mammals that have antlers. They are all ruminants. These include Deer, Elk, Moose, and Caribou.

Chaining

An Animal Behavior term describing sequences of behavior in which actions occur in a series, each one leading to the next. Within an Animal, this may be because one activity brings the Animal into the situation where the next is stimulated. Chaining may also occur between Animals, for example in courtship, where each partner often responds to the previous action of the partner in a series that leads to mating.

Chalk

The white, powdery variety of limestone from which blackboard chalk is made, chalk is composed of the remains of microorganisms that once drifted near the surface of the sea. When they died, their calcium carbonate skeletons rained down to the ocean floor and accumulated over the course of millions of years into layers many feet thick. Compacted into rock, the beds eventually were uplifted and exposed on the surface. The most famous chalk formations are the White Cliffs of Dover along the English Channel, but chalk beds were also deposited in shallow seas that once covered parts of North America, and can be seen in Alabama and Kansas.

Chamomile

Two common herbs are called chamomile, and they have much in common. Both have feathery, pale green foliage; pretty, daisylike flowers; and when crushed, a sweet, applelike aroma. Both, moreover, came to our shores in the baggage of European immigrants and have a long history of use among herbalists. Chamomile tea, brewed from the dried flowers of either kind, still is taken as a gentle, pleasant remedy for insomnia and upset stomach. The smaller of the two species, usually called true or Roman chamomile, grows only about nine inches tall and is the more fragrant of the two. The other, wild or German chamomile, at two to three feet in height, towers over its smaller cousin.

Chaparral

Taking its name from a Spanish word for scrub oak, chaparral is a specialized plant community made up of broad-leaved evergreen shrubs. Growing in dense thickets up to 15 feet high, it is found in hot, dry foothills from Arizona and Baja California northward through coastal California to southern Oregon. In addition to scrub oaks, the plants include manzanitas, chamisos, hollyleaf cherries, and dozens of other species. Although seemingly impenetrable, these tangles of vegetation are havens for hosts of animals, from lizards and packrats to wrens and thrashers. As part of the chaparral's natural cycle, thousands of acres fall victim to wildfires every year in the wake of the hot Santa Ana winds.

Chaparral biome

The Chaparral biome is found in a little bit of most of the continents. On the North American continent, it is found on the west coast of the United States.

Lay of the land: The chaparral biome has many different types of terrain. Some examples are flat plains, rocky hills and mountain slopes. It is sometimes used in movies for the "Wild West".

Chaparral is characterized as being very hot and dry. As for the temperature, the winter is very mild and is usually about 50 degrees F. Then there is the summer. It is so hot and dry at over 100 degrees that fires and droughts are very common.

Fortunately, the plants and animals are adapted to these conditions. Most of the plants have small, hard leaves which hold moisture. Some of these plants are poison oak, scrub oak, Yucca and other shrubs, trees and cacti.

The animals are all mainly grassland and desert types adapted to hot, dry weather. A few examples: coyotes, jack rabbits, mule deer, alligator lizards, horned toads, praying mantis, honey bee and ladybugs.

Char

Salvelinus

Prized by anglers and gourmets, the beautifully speckled chars are relatives of salmon and trout. In fact, both the brook trout and the lake trout are actually chars; they differ from true trout in having smaller scales and paler spots. Chars thrive in cold, clear waters across North America and spawn every autumn in the gravelly shallows of lakes and streams. The largest char, the lake trout, occasionally reaches 100 pounds, though most are caught before they reach 10 pounds. The brook trout is generally smaller but also puts up a challenging fight when caught. Other chars include the Arctic char, which inhabits northern waters and mountain lakes, and the Dolly Varden trout of the West.

Chemical (Industry)

Chemical industries are those involved in the importation, manufacture or sale of substances that are produced by or used in a reaction involving changes in atoms or molecules

Chemistry (Water)

The basic chemistry of water is hydrogen and oxygen, however unpurified water may also contain natural and human-made chemical pollutants.

Cheating

An Animal Behavior term, this is used to describe behavior believed to have evolved because the Animal showing it gains at the expense of other individuals. For example, male Scorpion flies present prey to females before mating, but some males cheat by mimicking females, flying off after accepting the gift and using it in their own courtship.

Cherry

Though modest compared to the splendid show put on by the ornamental cherries grown in parks and gardens, the spring flowering of our several native species nevertheless is a pleasant reminder of the progress of the season. The clusters of delicate, five-petaled, white flowers, like flurries of snow, contrast nicely with the shiny, reddish bark on the twigs. And the fruits that follow, though tarter than the imported cherries we grow in orchards, make tasty jams and jellies, as well as providing food for a wide variety of wildlife. The tallest and most valuable of our wild species is the black cherry, common in forests and fields throughout the East. Reaching a height of 100 feet, it is especially prized for its rich, reddish wood, which is second only to black walnut for fine cabinet work, decorative paneling, and musical instruments. Another species, found across the northern states and in the mountains south to Georgia and Colorado, is the pin cherry. It is also known as fire cherry because of the speed with which it follows in the tracks of forest fires. Its roots halt erosion, and its fallen leaves add humus to the soil, preparing the way for the forest's return. The most widespread of all the natives, the chokecherry is a common sight in hedgerows across most of the country. Its dangling clusters of pea-sized fruits are a boon to birds. Like some of the other wild cherry trees, though, its leaves can be a bane to any livestock that eats them; when the leaves wilt, a normally harmless substance contained in them is converted into the deadly poison cyanide.

Chert

A variety of quartz also known as flint and hornstone, chert is a dense, fine-grained sedimentary rock that has been valued for thousands of years. As early as the Stone Age, humans discovered that it can quite easily be chipped into sharp-edged tools and weapons. The first mineral to be deliberately mined, chert was fashioned into spearheads, knives, scrapers, and many other implements. In more recent times the rock again was used for weaponry when another of its properties, the ability to produce sparks, gave it a role as the firing device in flintlock rifles. Most commonly found as round nodules within other sedimentary rocks, chert also occurs in extensive, layered beds.

Chestnut

Castanea dentata

No tree was more esteemed by our early settlers than the American chestnut. Its soft but durable timber was used for cabins, rail fences, and furniture. And the sweet, glossy nuts, encased in spiny burrs, were a nutritious food for wild and domestic animals as well as for humans. Growing rapidly to a height of 100 feet, with a trunk up to 8 feet in diameter, the chestnut was king of the forest from Maine to Florida and westward almost to the Mississippi. Billions of the trees flourished throughout this range; in the Appalachian Mountains alone, their lanceshaped, coarsely toothed leaves shaded untold millions of acres. When the clusters of creamy flowers opened in June and July, the hills had the look of a rolling, foam-capped sea. Then, in 1904, a fungal blight appeared in New York City on chestnut trees imported from China. Within 50 years its spores had blown west, killing all but a few isolated specimens. Those that survived had been planted in western states, far beyond the tree's natural range. For decades, sprouts kept springing up from stumps of fallen chestnuts, but many of these too succumbed to the tragic blight. Valiant attempts were made to crossbreed the American chestnut in hopes of developing trees resistant to the fungus. But the experiments took decades and had mixed results. In recent years, however, plant pathologists have detected a weaker strain of the fungus, one that competes with the blight and enables infected trees to heal. By inoculating wild trees with this less virulent parasite, they hope to restore the American chestnut to its rightful domain.

Chickadee

Parus

Familiar inhabitants of woodlands and gardens and frequent visitors to feeders, chickadees are among our best-known songbirds. All are active, gregarious, friendly little creatures, with dark caps, black bibs, and gray or brown backs. Named for their cheerful "chickadee-dee-dee" calls, they also make a variety of piping and whistling sounds. While searching in trees for insects and insect eggs, these spirited acrobats often hang upside down from branches as they probe the bark with their bills. Chickadees nest in cavities in dead wood, in abandoned woodpecker holes, and sometimes in birdhouses. Both male and female share in incubation and all the duties of caring for the young. After the fledglings leave the nest, they gather in small, chattering flocks that roam the woods in winter foraging for food. The common species across the northern states and Canada is the black-capped chickadee; the nearly identical Carolina chickadee lives in the southeastern states. The mountain chickadee, with a distinctive white eyebrow, makes its home in the western mountains, and the ruddy chestnut-backed chickadee is found in humid forests and parklands along the Pacific coast. The boreal chickadee, also a northern bird, is the most drably colored of the group. During the winter months, if food supplies run short, flocks of these "brown-caps" sometimes stray well to the south in search of seed.

Chickweed

Stella ria media

Found in lawns and gardens all across the continent, chickweed grows in a sprawling tangle of stems. Commonly regarded as a nuisance, it is a persistent weed that often remains green throughout the winter; its tiny white starlike flowers bloom even when there is snow on the ground, yielding a continual crop of round, reddish-brown seeds. The plant appeals to a variety of animals, however, and the popularity of its seeds with birds both wild and domestic has given chickweed its name. Some people also eat the plant; its tender little leaves and stems, when tossed in salads or served as a hot vegetable, are a tasty substitute for spinach.

Chicory

Cichorium intybus

So common are the chicory's sky-blue, asterlike flowers by mid-July that it would be hard to imagine American roadsides without this tall, branching perennial. Yet it is not a native plant; its first reported appearance on this continent came in 1785, when Governor Bowdoin of Massachusetts imported its seed from Holland. He may have had a taste for the rosettes of tender, dandelionlike leaves the plant produces in its first year of growth; these are still grown for use as a salad green. But it is more likely that he planned to harvest the fleshy taproots, roasting and grinding them to flavor his coffee as the Creoles of Louisiana do today. Unlike many foreign weeds, chicory, which prefers dry soils, has never become a serious pest on farmlands.

Chinook

Mainly a winter phenomenon, the chinook is a warm, dry wind that sometimes rushes down the eastern slopes of the Rocky Mountains. Spilling onto the northern plains, it can cause temperatures to rise dramatically. On January 22, 1943, for instance, the temperature at Spearfish, South Dakota, jumped 49 degrees- from _4°F to 45°F -within a matter of minutes. Because such winds can rapidly melt any snow cover, chinooks are often called "snow eaters."

Chipmunk

Tamias

Small, striped, ground-dwelling squirrels, chipmunks are widespread across much of North America. The reddish-brown eastern chipmunk is found nearly everywhere east of the Great Plains; the least chipmunk is the most common of more than a dozen smaller, paler western species, which thrive in deserts as well as forests. Active by day, these bold and curious rodents tend to be most conspicuous in the fall, when they dart about in search of food for the coming winter. They stuff their roomy cheek pouches with seeds and nuts, which they then cache in their underground nests. And they live up to their scientific name, Tamias, which derives from a Latin word for treasurer: in three days, one eastern chipmunk took in 5 quarts of hickory nuts, 2 quarts of chestnuts, and about 24 quarts of shelled corn; the hoard of one of the western species contained over 67,500 items. During the winter, chipmunks sleep for long periods, waking regularly to feed. In the spring they emerge to mate, and a litter of two to six young is born about a month later.

Chiton

Insect term. The primary component of the external skeleton of crustaceans and insects.

Chiton

Molluscan term. Often exposed at low tide as they cling to seaside rocks, chitons are primitive, oval-shaped mollusks covered by eight overlapping plates. By day a large muscular foot on the underside holds them firmly in place; at night they creep about feeding on algae scraped from the rocks with a rasping, tonguelike organ. While most are only an inch or two long, one Pacific species grows up to a foot in length.

Chlorophyll

The green pigment found in plant tissue and essential for photosynthesis.

Cholla

Opuntia

A large and varied group, the chollas include cacti that sprawl in tangles several yards across but only a foot or so high, as well as others such as the jumping cholla that are branching, treelike, and grow up to 15 feet tall. All, however, are studded with a fearsome armament of spines, which are often up to 21/2 inches long. The spines protect the cactus wrens and thrashers that nest among the cholla's thorny branches. Pack rats also gather fallen joints of the cholla's cylindrical stems and build imposing, intruder-proof nests that are up to two feet high and eight feet across. For the cacti themselves, the spines function as much for reproduction as for defense. They catch on passing animals, which pull away short sections of the stems and carry them off to new locations; eventually the pieces drop to the ground and take root as new plants.

Christmas Bird Count (formerly "Census") (CBC)

Bird Biology Avian Conservation term.

An annual project, in the Americas, involving a one-day count in December of the individuals of all species observed within a circle that is 15 miles (24 km) in diameter.

Chuckwalla

Sauromalus obesus

A large, dark, stout-bodied lizard that sometimes reaches nearly a foot and a half in length, the chuckwalla lives on dry rocky hills in southwestern deserts. It is active during the day, appearing on rocky ledges early in the morning and basking in the sun until its body temperature rises to about 100~. Then, climbing about in creosote bushes, a favorite food plant, it forages for buds, fruit, flowers, and leaves. When threatened by predators, the slow-moving chuckwalla escapes by slipping into crevices among the rocks and inhaling large quantities of air; swelling up until it nearly doubles in size, the lizard becomes so securely wedged in place that it is almost impossible to dislodge.

Cicada

One of nature's most intriguing spectacles is provided by periodical cicadas, insects that emerge from the ground at 17 -year intervals in the North and on a 13-year schedule in the South. Appearing in huge numbers, the cicadas first shed their nymphal skins, which can often be seen clinging to trees and other supports like ghostly duplicates of the insects themselves. Then the cicadas move higher into the trees, where they mate, lay eggs, and-most notably- sing. Males serenade females by vibrating membranes on the sides of the abdomen. Their loud trills and soft buzzes, produced by throngs of insects, make up a deafening chorus. After mating, females insert their eggs in twigs, and the hatched nymphs later drop to the ground, burrow into the soil, and begin sucking juice from the tree's roots. After years of feeding in the dark, the nymphs tunnel to the surface, emerge as adults, and repeat the cycle. Often erroneously called locusts, cicadas are not related to true locusts, which are a kind of grasshopper. The periodical cicadas look like giant, broad-headed flies with bright red, bulging eyes and four transparent wings. Like their relatives the aphids and leafhoppers, they have mouthparts adapted for sucking plant juices. Similar to the periodical cicada are the dogday cicadas of the Northeast and the grand western cicadas of the Southwest. Both differ from the periodical cicadas in their greenish color and their much shorter life cycles, which span just one or two years.

Cinquefoil

Potentilla

The name cinquefoil means "five-leaf," and many of these perennial wildflowers and shrubs do indeed bear leaflets in groups of five, spread out like the fingers of a hand. Sometimes, however, the number varies; the shrubby cinquefoil, a dense, four-foot plant that ranges from Alaska to New Jersey, may bear leaflets in groups of 3 or 7, while other species have as many as 15 leaflets per leaf. The flowers, however, are more consistent in their arithmetic. The petals, usually yellow but occasionally white or crimson, always number five, and the many stamens invariably occur in multiples of five. The plants' generic name means "little potent one" and refers to the supposed medicinal properties of silverweed, one of the commoner species.

Circadian rhythm

An Animal Behavior term, this is used to illustrate a rhythm which is about one day in length, found in many aspects of behavior and physiology. Circadian rhythms often appear even in Animals kept under constant conditions, but they then usually "free run" at a length which diverges from 24 hours. In Nature, this intrinsic rhythm is entrained by the cycle of light and dark and so matched precisely to the 24-hour rhythm of the earth's rotation.

Cirque

Common features on glaciated mountains, cirques are steep-walled, basin-shaped hollows carved into the slopes. They were formed at the heads of glacier-filled valleys; plucking away blocks of underlying rock, the moving tongues of ice gradually excavated the hollows. With the glaciers now gone, the bottoms of the basins are often filled with the picturesque little mountain lakes known as tarns.

CITES

Endangered and Threatened species term.

The 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora, restricting international commerce between participating nations for plant and animal species believed to be harmed by trade.

CITES species

Species (675 as of this writing) listed under the 1975 Convention on International Trade in Endangered Species (CITES), which is administered by the United Nations Environment Programme. Such species cannot be commercially traded as live specimens or wildlife products because they are endangered or threatened with extinction.

Clam

Living on the bottom of oceans, rivers, and lakes, clams spend most of their time buried in mud or sand. Their soft bodies are protected by hinged, two-part shells of various shapes, depending on the species. The shell can be opened and closed, allowing a muscular foot to protrude. The foot propels the animal across the bottom by expanding and contracting in such a way that the clam alternately anchors the tip in the sand and then pulls itself forward. Clams eat and breathe by drawing water into the shell through a fleshy tube called the siphon, then passing it across their gills and expelling it through another tube. They feed on microscopic bits of food that become trapped in mucus on the gills. Since clams have no need to move about in search of prey, they can remain buried indefinitely on the bottom. Many of the clams are popular as seafood. One of the commonest kinds along the Atlantic coast is the quahog, or hard-shelled clam, which is often served in chowder and on the half shell. Another, the eastern surf clam, grows up to nine inches across. Soft-shelled clams, with shells that are more fragile than those of other species, are known familiarly as steamers.

On the Pacific coast, the eight-inch Washington clam, or gaper, can squirt a three-foot stream of water when disturbed. Another, the pismo clam, may live for 25 years. And the geoduck (pronounced "gooey duck"), sought as a delicacy, can weigh as much as 12 pounds. Freshwater clams, called river mussels, are less well known and less palatable than their marine cousins. Darker on the outside than sea clams, they are often harvested for their pearly inner shells, which are used for making buttons.

Clamworm

Well known to fishermen who often use them as bait, clamworms once were thought to prey on clams because they were sometimes found in empty clam shells. In fact, most of these marine worms live in burrows or under rocks and snatch small animals that pass within their reach. During the mating season, some species swarm to the surface and perform a kind of nuptial dance as they spawn. The larvae drift for a time with the plankton, then settle to the bottom for the rest of their lives.

Clarkia

Clarkia

Some three dozen species of these charming annuals ornament the western states. Growing up to three feet tall, the clarkias tend to prefer dry open areas such as the slopes and foothills of the Sierra Nevada and the Coast Ranges. An outstanding attraction of these four-petaled wildflowers is suggested by one of their colloquial names, farewell-to-spring. Blooming at the onset of hot weather, the clarkias open their pink, lavender, or white blossoms after most other wildflowers have faded and the turf has begun to brown with drought.

Classification

Biological Philosophy term. Linnaeus classified all known plants and animals and devised a system of naming plants and animals. The system assigns a two-word Latin name to each organism: the first word is the genus; the second, often descriptive, is the species name. For example, the house cat has the scientific name Felis domesticus; the lion, is Felis leo. He became interested in classification while studying the stamens and pistils (male and female sex structures) of flowers. He used the numbers of these structures to classify all known flowering plants in his Systema Plantarum (1753). His Systema Naturae (1758) classifies more than 4,000 animals, even human beings. Linnaeus first gave humans the scientific name Homo sapiens.

Classification

In order to study nature, scientists have classified the life forms in nature, or put them into groups. Organisms are classified according to how closely they are related. Large groups are broken down into smaller and smaller groups. A kingdom is the largest unit of classification. There are five kingdoms in nature. One of those kingdoms is Animalia, or the animal kingdom.

There are two main groups of animals: vertebrates and invertebrates. Vertebrates are a subgroup of the Phylum Cordata, or animals that have a spinal chord. These include fish, amphibians, reptiles, birds and mammals. You might not think it, but invertebrates, or animals without a spinal chord, make up most of the animal kingdom. These include sponges, jellyfish, worms, arthropods (insects, shrimp, spiders), mollusks (snails, clams, octopuses), and echinoderms (sea urchins, sea stars).

Organisms in the animal kingdom consist of many different species. Some animals most familiar to us are mammals, birds, fish and insects.

Animal cells don't have the rigid cell walls that plant cells have. Most animal bodies are made up of organized cells that are specialized to perform a specific task. Other cells are organized into even more specialized organs. Most animals are capable of moving relatively fast, unlike plants. Most animals reproduce sexually.

All told, around 9 or 10 million species of the kingdom Animalia inhabit the earth; the exact number isn't known. Most of them are in the Arthropod phylum, or animals with jointed legs, like insects and crustaceans. In fact, some scientists believe that if we were to identify all species in the tropical rain forests, the ranks of Arthropoda would be over 10 million species.

Clay

An extremely fine-grained earthy material that can be molded when moist but hardens when dried or fired, clay is an important component of soil. It also is a valuable resource that has been used for centuries in architecture and industry. Its numerous applications range from the manufacture of bricks, fine china, and high technology ceramics to the coatings that give book papers their whiteness and glossy shine.

Clean-Up (Water)

Cleaning up a chemical spill in water involves trying to physically contain the spill and prevent it from coming into contact with sensitive ecosystems, as well as removing the pollutant itself through the use of such technologies as oil skimmers or the introduction of a degrading substance.

Clematis

Clematis

Most of the wild clematises, like their cultivated cousins, are vines. Their leafstalks coil around the twigs of neighboring shrubs and so help hoist the plants up into sunlight. The most common species in the East is virgin's bower, a vine that scrambles over streamside brush. Its other common name, old-man's beard, was inspired by the clustered fruits, each one tipped with a long silky plume. A few of the clematises are not vines at all, but upright, earthbound wildflowers. Typical of the nonclimbing sorts is the pine-hyacinth of Florida. Its knee-high stems bear as many as three blue or lavender bells in late winter.

Click beetle

Noisy little acrobats, click beetles are also known as skipjacks and snapping bugs-and with good reason. When threatened, the inch long insects drop to the ground and play dead. If they happen to land upside down, they arch their backs, then snap them straight-an action that launches their bodies into the air with an audible click and, with luck, lands them on their feet again. One of the largest, commonest, and most conspicuous North American species, the eyed click beetle is easily recognized by the pair of large eyelike spots on its back. The larvae of click beetles-hard and wiry-are called wireworms. Burrowing through the soil and feeding on seeds and roots, many of them are serious agricultural pests.

Climate

The difference between weather and climate is, in effect, the difference between days and decades. Weather, which changes daily, includes such things as the temperature, wind, rain, snow, and cloudiness at a particular time and place. An area's climate, in contrast, is the average pattern of weather that occurs there over tens or even hundreds of years. Among the factors influencing a region's climate are its latitude, its distance from the sea, and the existence of mountain barriers. Widely varying conditions in North America result in such extremes as the humid, subtropical climate of southern Florida and the hot, dry climate of the southwestern deserts. Although in the course of a human lifetime climate appears to be fixed, it can in fact change. Some 20,000 years ago, for example, much of North America was covered by glacial ice-and many scientists believe that such ice ages recur in cycles. In more recent times, the amount of carbon dioxide in the atmosphere has been increasing as a result of the burning of fossil fuels. Preventing the escape of heat from the earth the so-called greenhouse effect-this build-up of carbon dioxide could, over a long period of time, cause a gradual warming of climates all around the world.

Climate Change (UF Global Warming)

Human activities are altering the chemical composition of the atmosphere through the build-up of greenhouse gases that trap heat and reflect it back to the earth's surface. This is resulting in changes to our climate, including a rise in global temperatures and more frequent extreme weather events.

Climate change

Changes in the global climate system in response to physical feedbacks, chemical feedbacks, and changes in terrestrial and aquatic systems caused by humans and nature.

Climate facts

The sun's rays hit the equator at a direct angle between 23 ° N and 23 ° S latitude. Radiation that reaches the atmosphere here is at its most intense.

In all other cases, the rays arrive at an angle to the surface and are less intense. The closer a place is to the poles, the smaller the angle and therefore the less intense the radiation.

Our climate system is based on the location of these hot and cold air-mass regions and the atmospheric circulation created by trade winds and westerlies.

Trade winds north of the equator blow from the northeast. South of the equator, they blow from the southeast. The trade winds of the two hemispheres meet near the equator, causing the air to rise. As the rising air cools, clouds and rain develop. The resulting bands of cloudy and rainy weather near the equator create tropical conditions.

Westerlies blow from the southwest on the Northern Hemisphere and from the northwest in the Southern Hemisphere. Westerlies steer storms from west to east across middle latitudes.

Both westerlies and trade winds blow away from the 30 ° latitude belt. Over large areas centered at 30 ° latitude, surface winds are light. Air slowly descends to replace the air that blows away. Any moisture the air contains evaporates in the intense heat. The tropical deserts, such as the Sahara of Africa and the Sonoran of Mexico, exist under these regions.

Climax

An assumed final state of stability in the reconstitution of a destroyed ecosystem. The endpoint of a successional sequence; a community that has reached a steady state under a particular set of environmental conditions.

Climax community

Ecologists have long recognized that any plant community-the association of species growing on a given site-tends to change over time in the process of natural succession. Eventually, however, a state of equilibrium is reached; the species are so finely attuned to each other and to the overall environment that changes cease. This stable, self-perpetuating mix of vegetation is called the area's climax community. Only a change in climate, a catastrophic event such as a forest fire, or more often, man's interference will alter the vegetation.

The nature of the climax community is determined by climate, soil, and other environmental factors. The abundant precipitation and mild winters of central North Carolina, for instance, foster an oak/hickory climax-a hardwood forest dominated by those trees. And Oklahoma's hotter summers, colder winters, and periodic drought result in a tallgrass prairie.

Cline

A geographic gradient in a measurable character, or gradient in gene, genotype, or phenotype frequency.

Clingfish

Shaped more or less like tadpoles, these scaleless, broad-headed bottom dwellers are made for the sedentary life: on their undersides, the pelvic fins are fused into suction discs that enable clingfish to get a grip on rocks, oysters, and other hard surfaces, and so steady themselves against the ebb and flow of the tide. Even when plucked from the water, they sometimes hold fast to their moorings. Clingfish are most common in tropical seas, but the hardy skilletfish-named for its fryingpan shape- is often seen in oyster beds as far north as New Jersey. In the West, the northern clingfish, large at six inches, ranges all the way to Alaska and lives in kelp beds.

Clintonia

Clintonia

Bride's bonnet is the common name of the western clintonia, and the one or sometimes two dainty white blossoms that top its 18-inch stems in early summer would indeed be suitable adornment for a bride. Also called queen cup, this graceful perennial produces bright blue berries, a characteristic it shares with a clintonia found in northern California and Oregon. The bluebead, or dogberry, of northeastern forests and bogs also bears blue fruits. The only nonconformist is the speckled wood lily of eastern mountains; its berries are pitch black.

Cloud

Everyone, no doubt, has marveled at the sight of billowing, cottonlike clouds drifting slowly overhead and changing constantly in size and shape. Substantial as they may seem, however, these fantastic sky sculptures are nothing more than water vapor made visible. They form when warm air rises and cools, causing the water vapor in it to condense into tiny droplets or ice crystals. And these droplets and crystals are what we see as clouds. Based on their appearance, clouds are classified into three basic types: cumulus, or heaped; stratus, or layered; and cirrus, or wispy. The shapes of clouds are significant because they can help us predict coming changes in the weather. Fleets of mile-high, puffy, cumulus clouds, for instance, indicate fair weather. If very large cumulus clouds develop and their domes rise five miles or more into the sky, their tops often spread out into the shape of an anvil. Such ominous-looking clouds are described as cumulonimbus (nimbus means rain) and usually foretell impending thunderstorms and heavy rain. Stratus clouds form when there is little wind and a warm front flows across a wedge of colder air. Uniform in appearance, these layered clouds often lie close to the ground and may produce drizzle or light rain. In contrast, wispy cirrus clouds, also known as mares' tails, form at very high altitudes and are composed of ice crystals; advancing ahead of a front, they usually indicate the approach of rain or snow.

Clover

Trifolium

Distinguished by their three-part leaves and dense, fragrant flower heads, clovers are a familiar element in many American landscapes; they thrive in lawns, fields, vacant lots, roadsides virtually everywhere. Although we have several native species, almost all the common cultivated clovers are imports that have long since spread across the country. White clover and crimson clover, from Europe, were introduced as forage crops; both are also valued as honey plants. Red clover, another immigrant and the state flower of Vermont, is one of the more important species grown for hay. In lawns, however, the clovers are sometimes regarded as pests. But turf purists who try to eradicate them do so at their own expense, since clovers, like other members of the pea family, have nodules on their roots that host nitrogenfixing bacteria. These valuable microorganisms enrich the soil by converting atmospheric nitrogen into a form usable by plants-and nitrogen is the major active ingredient in most lawn foods. Appreciating their value as natural fertilizers, farmers often sow clovers in their fields to be plowed under as "green manure."

Clubmoss

Despite their name and sometimes mossy appearance, clubmosses are not mosses at all. Growing in woodlands, bogs, and meadows, many of these low-growing evergreens, such as ground pine and running cedar, have narrow, scalelike leaves and are topped by erect, clublike cones. Looking much like miniature conifers, they are, in fact, related to ferns and horsetails. They are the descendants of huge prehistoric trees that flourished hundreds of millions of years ago-in the forests that later were transformed into tremendous coal deposits. Clubmosses spread mainly by means of long, wiry stems that creep across or just under the ground and send up new shoots every few inches, but they also reproduce by means of spores. The clublike structures atop the plants-or in some species, the tiny sacs at the base of the leaves-produce the fine, yellow, dustlike spore granules that are dispersed by the wind. When the spores settle to the earth, they develop into tiny plants that live hidden underground for years before emerging as adults.

Coal

One of our most important and abundant mineral resources, the coal that we burn today had its beginnings hundreds of millions of years ago in vast prehistoric swamps. Forests of gigantic, fernlike trees up to 100 feet tall and 6 feet in diameter flourished in these wetlands, along with amphibians 8 feet long and dragonflies with 2-foot wingspans. When the plants died, their remains accumulated into layers many feet thick and gradually decomposed into peat. Layers of sediment eventually were deposited over the peat, and heat and pressure transformed it into coal. Fern fronds and other fossils from the prehistoric forests are often found preserved in coal seams-compelling evidence of their origin as living plants. Variations in conditions produced different kinds of coal in different areas. Ugnite, the type most like peat, is soft, crumbly, and brown. Bituminous, or soft, coal-by far the most abundant sort-is dull black and harder than lignite. Anthracite, produced by tremendous pressures generated by folding of the earth's crust, is extremely hard, black, and shiny; almost pure carbon, it burns the most efficiently of any coal.

Coarse-grained

Referring to qualities of the environment that occur in large patches with respect to the activity patterns of an organism. This results in the organism's ability to select usefully from among qualities.

Coati

Nasua narica

A lively relative of the raccoon, the coati ranges just north of the Mexican border into southern Arizona, New Mexico, and Texas. Foraging by day with its long, striped tail held high, this 15to 25-pound mammal eats almost anything, from prickly pears to tarantulas. It probes the earth with its nimble snout in search of grubs and roots but also takes small prey such as scorpions and lizards. Leaping into trees like troops of monkeys, coatis feast as well on eggs, nuts, and especially, fruit. An agile climber, it uses its tail as a balancing pole on the way up and as a holdfast on the way down. Females and young males feed, nap, groom, and play in boisterous bands of a dozen or more. Adult males, however, are loners and join the groups only during the breeding season. Some seven weeks after mating, the females retire to tree nests or rock dens and give birth to four to six kits. There they remain until, about five weeks later, the noisy young are brought forth and introduced to high-spirited coati society.

Cobia

Rachycentron canadum

With no close kin among any fish in the sea, the cobia is one of a kind. Sleek and fast-moving, it has a long, dark body, a pointed snout, and a line of short spines in front of the dorsal fin. While they are usually one to four feet long and weigh 30 to 50 pounds, specimens more than five feet long and weighing as much as 100 pounds have been hooked. Traveling alone or in small schools, cobias rove warm inshore waters and are often seen hovering beneath larger fish, boats, buoys, and other floating objects. Most prefer the balmy Gulf of Mexico, but during the summer some cobias travel north to brave the cooler waters off New England. Voracious predators, their keen appetite for crustaceans has earned them the nickname crabeaters.

Cockroach

With a lineage of some 350 million years, cockroaches are obviously born survivors. Voracious eaters, they feed on almost anything, including paper, soap, and glue. Usually dark brown or black, with a flattened oval body, cockroaches are creatures of the night that, with few exceptions, scuttle frantically away from light. Body hairs that are sensitive to air currents and sound vibrations warn them of approaching danger; long legs and lightning reflexes help them dash to safety. While many species have wings, most household varieties do not fly. Fifty-five species of cockroaches are found in North America. Luckily, only five of them are household pests; the majority live outdoors in plant litter, woodpiles, and crevices. The giant palmetto bug of Florida, at more than two inches in length, is North America's largest cockroach. More common and much smaller is the Croton bug, or German cockroach, which is found in urban dwellings all around the world.

Codfish

Abundant and valuable food fish-annual catches amount to tens of thousands of tonsseveral members of the codfish family are prized for their tasty flesh. The premier member of the family, the Atlantic cod, has in fact been so vital to the Massachusetts economy since colonial days that a large carving of the fish is prominently-and proudly-displayed in the State House in Boston. Dark-spotted, with three back fins and a single chin whisker, Atlantic cod live in cold waters and probe the ocean bottom for a variety of foods. Active predators, they eagerly devour other fish, squid, and shellfish, often swallowing the shells along with the flesh inside. The average cod hauled in by fishermen weighs less than 25 pounds, but they can grow to great size; the record holder was a hefty 200-pounder. Other important members of the codfish family include the Pacific cod, found in waters off the northwest coast; haddock, which live in the north Atlantic and are among the most valuable of all food fish; tomcod and pollock, found off both coasts; and the burbot, a freshwater codfish found in northern lakes.

Coitus

Sexual intercourse, also called coitus, or simply sex, is to have sex is the human form of reproduction. In humans this is performed relatively frequently, and primarily for sexual pleasure rather than in response to a seasonal stimulus. To engage in sexual intercourse, the erect penis is inserted into the vagina and one or both of the partners move their hips to move the penis backward and forward inside the vagina to cause friction, and an increasingly rapid back and forth motion, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasms are achieved. Penetration by the hardened erect penis is also known as intromission, or by the Latin name immissio penis.

Coltsfoot

Tussilago farfara

One of the earliest of spring flowers, coltsfoot seems intent on getting a head start on the season: its yellow, dandelionlike blooms open atop scaly 4- to 18-inch stems, then wither and set seed before any leaves appear. Because of this two-stage growth pattern, herbalists called the plant son before the father. When the large, roundish leaves do unfurl, they explain coltsfoot's common name; toothed along the edge, they are shaped more or less like a hoofprint.

Columbine

Aquilegia

Their delicate blue-green leaves and dainty flowers may have an appearance of great fragility, but columbines are tough. Blue columbine, for instance, the state flower of Colorado, climbs well above timberline on its native peaks, while the yellow-blossomed Chap line's columbine sprouts from desert cliffs in New Mexico. Even the red and yellow wild columbine of eastern North America ventures out of its preferred moist woodlands to colonize rocky crevices and ravines. Although the color varies from species to species, the form of the flowers remains the same: each of the five petals extends backward in a long, pointed tube, or spur. Our ancestors likened the blooms to five birds perched around the edge of a fountain, and the plant's name derives from the Latin for "like a dove."

Comb jelly

Sometimes seen dotting sandy beaches after storms or drifting at the surface in quiet lagoons, comb jellies look like small, transparent blobs of gelatin. No relation to the true jellyfish, they are named for the eight rows of comblike projections that circle their body like lines oflongitude on a globe. Moved in unison, the combs propel the creatures weakly through the water. By day, sunlight reflects off the moving combs, producing an iridescent glint; at night the animals sometimes glow in the dark with a lovely greenish or bluish light. Most comb jellies feed by sweeping tiny planktonic organisms into their mouth with their long, sticky tentacles. Common species include the sea gooseberry, less than an inch in diameter, and the pinkish, two-inch sea walnut.

Comfort movements

An Animal Behavior term, this is used to refer to a varied group of activities including grooming, scRatching, shaking, stretching and yawning.

Comfrey

Symphytum officinale

An immigrant from Europe that now grows wild on roadsides and in waste places, comfrey is abuzz with activity when it blooms, for bees find its dangling clusters of pink, blue, or yellowish bell-shaped flowers irresistible. The plant's large, hairy leaves supplied generations of countryfolk with salad greens and pot herbs, and they were traditionally used in a variety of herbal remedies. Unfortunately, however, while the foliage is rich in protein, vitamins, and minerals, the plant has also been found to contain a cancer-causing alkaloid, particularly in its long, black-skinned root. No longer recommended for internal use, the leaves nevertheless can be crushed and safely applied to wounds as a soothing poultice.

Common name

The nonscientific name of an animal or plant most widely used and accepted by the scientific community.

Commons

Biological Philosophy term. "The global commons": Those resources we all have to use to survive but which we do not have to pay for. The term is based on the idea of the village commons: a plot of land owned by no one where all had the right to graze their stock. Because its use was without cost, people overused it, not respecting its fragility or limits or expending any effort or resources to preserve it. The inevitable result was the destruction of the commons. By application, the "global commons" are threatened with overuse precisely because we do not figure in a cost for them. There is a cost, of course, that we are paying all the time, in the diminution or damaging of the commons.

Commensalism

An Animal Behavior term, this is used to explain an association between two species such that one of them benefits without appreciable cost to the other. Examples are Scavengers, and predatory Fish that live in shoals of harmless ones so gaining Camouflage from which they can attack prey.

Community (Action and Learning)

All of the people living in a specific locality or members of a group that share a particular interest.

Community

A group of organisms, generally of wide taxonomic affinities, occurring together. Many will interact within a framework of horizontal and vertical linkages such as competition, predation, and mutualism.

Competition

An interaction between members of two or more species that, as a consequence either of exploitation of a shared resource or of interference related to that resource, has a negative effect on fitness-related characteristics of at least one of the species.

Compliance (Law)

Compliance means conformity with the law. Government ensures compliance with legislation through two types of activity: promotion and enforcement.

Composting (Recreation)

Using decomposing vegetable matter, including table scraps, grass clippings, leaves, peat and soil to fertilize the soil. Composting reduces the amount of waste sent to landfill, and helps put valuable nutrients back into residential and commercial gardens.

Compound eye

The eye structure typical of insects and some other invertebrates comprising numerous cells and lenses, not a single lens.

Conch

Found in warm, shallow tropical seas, especially off the Gulf Coast and southern Florida, conchs (pronounced "conks") are large, spiral-shelled marine snails. Docile plant eaters, conchs move quickly across the sandy bottom by means of a horny, clawlike plate attached to the end of the muscular foot. By digging the claw into the sand and quickly contracting a muscle, conchs can actually leap or somersault. Queen conchs, prized by collectors for their beautiful pink shells, are up to a foot long and weigh as much as five pounds. Florida fighting conchs, about four inches long, are particularly agile leapers, hence their name. Conch flesh is used in fritters and chowders, and the shells are occasionally fashioned into horns for signaling.

Conditioning

An Animal Behavior term, this is used to define learning by association. In classical conditioning, two stimuli are associated so that the second comes to elicit a response formerly only elicited by the first. In Instrumental or OperAnt conditioning, the Rate of a response is raised or lowered by its association with Reinforcement.

Condor

Gymnogyps californianus

With a nine-foot wingspan-the greatest of any North American land bird - the California condor used to be a master of the sky. Now rare and seriously endangered, this extraordinary vulture once soared high above the land, gliding 10 miles at a time without flapping its wings. Thousands of years ago the birds ranged east as far as Florida, feeding on the carcasses of once-plentiful large mammals, but by the middle of this century, the huge, cliff-nesting birds were confined to the mountains of southern California. Raising only one young every other year and beset by habitat loss, food shortages, and contamination of their food with pesticides and poisons, their numbers dropped to fewer than 40 by 1975. In the mid-1980's the remaining wild birds were captured and placed in zoos, where only a few young have so far been successfully hatched. Researchers are trying to build up a population of captive-bred condors and hope eventually to return them to the wild.

Cone

The structure bearing reproductive elements of conifers.

Conference

Endangered and Threatened species term.

The consultation process required for Federal actions that are likely to jeopardize the continued existence of a species proposed for listing or result in the destruction of adverse modification of proposed critical habitat.

Conflict

An Animal Behavior term, this is used to explain a situation when an Animal with an approximately equal tendency to do two things at once is said to be in a Motivational conflict. Thus, a hungry Animal beside whose food a frightening object is placed is in an approach-avoidance conflict. In such a balanced state, Animals often show other, seemingly irrelevAnt, behavior (see Displacement Activity). Many courtship displays are thought to have arisen from such actions produced as a result of conflict.

Coneflower

The cheerful, golden yellow rays encircling a dark, domed center have fixed the name blackeyed Susan in the minds of flower lovers all across the continent. But the black-eyed Susan is just one of many coneflowers, members of the sunflower family with petallike ray flowers that surround a thimblelike cone of disc flowers. The prairie coneflowers, found on the Great Plains and eastward, have drooping yellow ray flowers, and their cones give off a licoricelike aroma when crushed. The purple coneflowers, also native to the plains, have more bristly cones. Their lovely, magenta flowers are prized by gardeners.

Conglomerate

Naturally cemented jumbles of rounded stones, conglomerates are a type of sedimentary rock. The pebbles they contain usually were worn smooth as they were rolled and bounced along by fast-flowing water in ancient streams. When the stones eventually came to rest, the spaces between them filled with smaller grains and the mass was gradually cemented together to form the potpourri referred to as a conglomerate.

Conifer

A tree that bears its reproductive structures in cones. The scaled cones that protect the seeds of conifers come in a variety of shapes and sizes and are one of the main distinguishing characteristics of these trees and shrubs. Their needlelike leaves are another feature common to conifers, although cedars and junipers, for example, have flat, scalelike leaves instead. Most also are evergreen: the exceptions are the larches and bald cypresses, which lose their needles in winter.

An ancient order of plants, the conifers developed millions of years ago, long before the first broad-leaved trees. Their stately descendants include our oldest trees (the 4,600-year-old bristlecone pines), our biggest (the giant sequoias), and our tallest (the California redwoods). Cones not at tips of branches Bracts between cone scales. Broad-leaved trees are better adapted to temperate climates, however. The conifers are dominant in northern regions where the evergreens' ability to make and store food year-round is a major advantage. Because needles are better at retaining water than broad, flat leaves, conifers also thrive in hot, dry areas and often on poor, rocky soils.

Connectedness

The structural links between habitat patches in a landscape; can be described from mappable features.

Connectivity

A parameter of landscape function that measures the processes by which a set of populations are interconnected into a metapopulation.

Conserve

Endangered and Threatened species term.

Carrying out actions to improve the health of a species so it no longer needs to be listed as threatened or endangered.

Conservation

Environmental conservation is a general term that refers to the preservation of the natural environment-including wildlife, habitat, and the ecosystems they are a part of.

Conservation

Endangered and Threatened species term.

From section 3(3) of the Federal Endangered Species Act: "The terms "conserve," "conserving," and "conservation" mean to use and the use of all methods and procedures which are necessary to bring any endangered species or threatened species to the point at which the measures provided under this Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transportation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking."

Conservation

Biological Philosophy term. The "wise use" of natural resources, managing nature rather than preserving it as untouched wilderness. Gifford Pinchot of the U. S. Forest Service is the name associated with wise use; John Muir is associated with the rival policy focusing on preservation of wilderness. Aldo Leopold was a student in the Pinchot tradition, but seems to have arrived at a balance between the two.

Consort relationship

An Animal Behavior term, this is used to describe a temporary Pair Bond between a male and a receptive female as found, for example, during mating season.

Constant-effort mist netting

Bird Biology Avian Conservation term.

A capture method, standardized over space and time, used for counting numbers of birds captured in mist nets.

Endangered and Threatened species term.

All Federal agencies must consult with the U.S. Fish and Wildlife Service (or National Marine Fisheries Service) when any activity permitted, funded, or conducted by that agency may affect a listed species or designated critical habitat, or is likely to jeopardize proposed species or adversely modify proposed critical habitat. There are two stages of consultation: informal and formal.

Consummatory act

An Animal Behavior term, this is used to define an act that terminates a behavior sequence and leads to a period of quiescence. Opposed to the Appetitive Behavior that leads up to it; thus, food seeking ends in eating, and mating in ejaculation.

Contact

A single field record of an individual by sight or sound (syn. detection, cue, registration, observation).

Contact call

An Animal Behavior term, this is used to refer to any sound which serves to keep members of a pair or social group in touch with one another. Contact calls are commonly produced by moving Animals, especially where visibility is poor.

Contamination (Water)

Water is considered contaminated if it contains chemical or biological pollutants that are harmful to human health or the environment.

Continental Divide

Gentle rivulets, rushing streams, and mighty rivers-all are affected by a line of high ridges in the Rocky Mountains that we call the Continental Divide. To the west of the line water flows toward the Pacific Ocean; to the east it flows into the Atlantic or the Gulf of Mexico. Marking the boundary between two drainage systems, the Continental Divide, sometimes called the Great Divide, continues north through Canada and south into Mexico. Lesser divides can also be traced. One, near Duluth, Minnesota, runs from east to west, separating the water flowing north into the Great Lakes and the St. Lawrence River from the water that flows south into the Mississippi.

Cottaging (Recreation)

Many people spend their summers at cottages located on the shores of lakes and rivers. Good cottagers make an effort to reduce their impact on the surrounding environment, particularly the sensitive aquatic ecosystem, by using non-polluting boats and innovative composting toilets.

Cooperation

An Animal Behavior term, this is used to define the situation in which Animals assist one another for mutual benefit. Thus, Animals in groups may assist one another in predator detection because they have more pairs of eyes. They may also be able to Catch larger prey through coopeRative hunting, as in certain Predators.

Coot

Fulica americana

Noisier and more quarrelsome than their relatives the rails, American coots are known for their unmelodic medleys of cackles, grunts, and croaks. Ducklike water birds, they are slaty gray with a white bill, red eyes, and lobed toes that facilitate both swimming and walking on muddy shores. The birds take flight awkwardly, spattering water as they run across the surface trying to lift off. Feeding on aquatic plants, insects, worms, and snails, coots often gather in dense flocks on open water. The young have a remarkable means of escaping danger: at the first warning from an adult, chicks dive underwater and grasp a plant stem in their bill, anchoring themselves to the bottom until the danger has passed.

Copepod

Tiny (the largest are no bigger than a grain of rice) but incredibly abundant, copepods playa vital role in oceanic food chains. These small, shrimp like crustaceans feed on microscopic plants and are in turn consumed in vast quantities by other invertebrates, as well as by fish and even whales. The copepod's body, enclosed in a protective shell like that of a shrimp, is equipped with two pairs of antennae and several pairs of flattened limbs. The limbs, in fact, give the copepod its name, which is derived from Greek words meaning "oar foot." In addition to the marine copepods, freshwater species live in ponds and quiet streams. Easily captured with a fine net, they can be observed with a hand lens.

Copper

A shiny, pliable, orange-red metal that is easily shaped and immune to rust, copper has been pounded into tools and implements since ancient times. It still is widely used for utensils, coins, and roofing. (The familiar greenish patina on copper roofs prevents further corrosion.) An excellent conductor of heat and electricity, copper also is used for pots, pans, wire, and tubing. In addition, it can be combined with other metals to form the alloys brass and bronze. Copper is sometimes found in its pure form (called native copper); on Michigan's Keweenaw Peninsula, it occurs in masses weighing up to several tons. More often, copper is mined as an ore, from which the metal is extracted.

Copperhead

Agkistrodon contortrix

up to 41/2 feet long, the copperhead is a poisonous snake named for the coppery color of its head. It lives in rocky, wooded areas from Massachusetts to Texas, where the chestnut-brown hourglass pattern on its back keeps it well camouflaged among fallen leaves. Copperheads are related to cottonmouths and rattlesnakes and, like those other pit vipers, have heat-sensitive organs on their faces that are used to locate warm-blooded prey. In addition to small mammals, they feed on lizards and frogs, which are killed by venom delivered through sharp, hollow fangs. Fortunately, their bite, though painful, is seldom fatal to humans.

Coprophagy

An Animal Behavior term, meaning the eating of feces. This is importAnt in some Animals to transmit organisms, which help to break down food, from one individual to another, such as from adult to offspring. Eating its own feces may also improve the efficiency with which an Animal utilizes its food. It is sometimes practiced by Rabbits and Picas.

Copulation

Copulation is the union of the external genetalia of two animals for the purpose of sexual activity and subsequent reproduction. The two individuals may be of opposite sexes or of the same sex. Animals initially lived only in water and reproduced by reproducing in the water. Certain animals started migrating from oceans to the land during the epoch about 450 million years ago, necessitating internal fertilization to maintain the developing offspring in a liquid medium.

Coquina

Oonax variabilis

Less than one inch long, the glossy-shelled Florida coquina is a pretty wedge-shaped clam found in the surf zone of sandy beaches from New York to Texas. Coming in a variety of pastel hues, these dainty little mollusks burrow into the sand with each receding wave, then resurface to feed on the next incoming wave. Despite their small size, coquinas make an excellent chowder, and their shells, compacted into rock, are used as a building material in parts of Florida.

Coral

Relatives of sea anemones and jellyfish, the stony corals are tiny invertebrates found in warm, shallow tropical and subtropical seas. Some live as solitary individuals, but most form large colonies. Each animal, called a polyp, is usually only a fraction of an inch long, and its tube-shaped body is fixed at one end to a limestone cup formed of its own secretions. At the other end is a mouth leading to a gullet, and around the mouth are tentacles used to sting small prey. Less common than the stony corals, soft corals have horny or leathery skeletons. Colonies of the stony corals grow in size by building on the skeletons of their ancestors. Different species develop characteristic and sometimes wonderfully exotic forms, as suggested by such common names as brain coral, lace coral, star coral, and elkhorn coral. Individual polyps reproduce by forming buds, each of which matures into a new polyp alongside the old one. The same corals also reproduce sexually; the fertilized eggs hatch into free-swimming larvae that, unlike the buds, can swim off on their own to begin new colonies.

Coralbean

Erythrina

Covered with showy spikes of tubular, brilliant scarlet blossoms, these handsome shrubs and small trees stage a dramatic show each year from late spring through early summer. The flowers are followed by pods of attractive, but poisonous, shiny red beans. The most familiar species are the eastern coralbean, which ranges from North Carolina to Texas, and the southwestern coralbean, native to the dry, rocky soils of Arizona and New Mexico. The buoyant, light wood of a Hawaiian coralbean is used for the manufacture of surfboards, floats, and similar items.

Coral reef

Individual coral polyps, the marine animals that spend their lives anchored in self-made limestone cups, are relatively small. Colonies of these little creatures, however, have created the largest structures ever produced by any living thing; generation after generation builds upon the limestone remains of their ancestors, forming underwater reefs that can continue to expand indefinitely. Found in warm, shallow seas off the coast of Florida and farther south, coral reefs support an incredible variety of life. Snails, crabs, and spiny lobsters creep through crevices in the coral rock. Starfish, worms, and parrot fish "graze" on the living polyps. And everywhere there are sea fans, sponges, and other exotic creatures. Divers have long been enchanted by coral reefs, where they marvel at the intricate formations of the corals themselves and the astonishing array of brightly colored fish that flit through these incredible underwater seascapes. Among the most fascinating reef dwellers are the small, low-profile cleaner fish, at whose "stations" the larger fish patiently wait in line to be nibbled free of parasites.

Coral snake

To recognize the difference between the colorfully banded, poisonous coral snakes and harmless look-alikes such as the scarlet kingsnake, generations of southern children have been taught a helpful ditty: Red next to black, a friend of Jack; Red next to yellow can kill a fellow. For only on coral snakes do the red and yellow bands touch each other. In fact, the snakes are seldom even seen; our two native species are mainly nocturnal and spend most of their time hiding under logs or in burrows. When people do encounter the smallish, handsomely banded reptiles, the snakes tend to be docile and bite only if handled. Sometimes called harlequin or candystick snakes, coral snakes live in a variety of locations and habitats, from dry, rocky slopes and canyons in the Southwest to pine woods and wet hammocks in the Southeast.

Cormorant

Phalacrocorax

Long-necked, duck-sized, and glossy black, cormorants are fast and efficient water birds. Diving underwater, they paddle furiously with their webbed feet and seize fish in their long, sharply hooked bill. Unlike most aquatic birds, they do not have water-repellent feathers and so can often be seen perched on rocks or pilings with their wings spread out to dry. Found along seacoasts and on inland lakes and rivers, cormorants are highly social; they sometimes form communal fishing groups that include hundreds or even thousands of birds. Assembling into long lines, they herd a school of fish toward the shallows and snatch those feeding near the surface. Cormorants also breed in colonies, building crude, bulky nests on rocky cliffs or in treetops.

The most widespread of the six North American species and the only one likely to be seen far inland is the double-crested cormorant, named for the pair of curly plumes it wears on the sides of its head during the breeding season. Others include the Brandt's and pelagic cormorants of the Pacific coast and the great cormorant, found along the Atlantic coast.

Corridor

A spatial linkage that facilitates movements of organisms among habitat patches in a landscape.

Cornetfish

Fistularia

Long, slender fish that sometimes reach a length of six feet, cornetfish have an elongated, tubular snout and a whiplike filament trailing from their tail fins. These near relatives of trumpetfish occur mostly in the West Indies, but in summer are found further north. Camouflaged by their vertical stripes and dark color, they swim just below the surface and stalk prey near corals and grassy seabed flats. They drift slowly toward unsuspecting small fish and feed by quickly sucking prey into their tiny mouth. The blue-spotted cornetfish ranges from Nova Scotia to Florida and the Gulf of Mexico. The less common red cornetfish travels only as far north as Virginia.

Cosmopolitan

Meaning that it is usually found worldwide in suitable habitat.

Cotton grass

Eriophorum

Despite their name, the cotton grasses are not grasses at all but members of the sedge family. In bloom from summer into fall, they bear tiny flowers amid tufts of long, cottony white hairs atop their triangular stems. Found in bogs and moist meadows all the way north to the Arctic Circle, the cotton grasses often grow in dense stands, their tufted white flower heads looking like unseasonable snow covering the land.

Cottonmouth

Agkistrodon piscivorus

Often spotted on branches overhanging water, cottonmouths are highly venomous snakes whose bite can be quite dangerous. When threatened, the snake rears its chunky head and gapes to display the cottony white interior of its mouth-hence the name. Also called water moccasins, they are closely related to the copperhead and infest swamps, rivers, lakes, and rice fields in the southern states. From two to six feet long, the cottonmouth has a broad flat head and stout body, either unpatterned or marked with dark, ragged blotches. Uke other pit vipers, cottonmouths have deep, heat-sensitive facial pits that detect warm-blooded prey. They also feed on frogs and insects.

Cotton rat

Sigmodon hispidus

One of three rats native to the United States, the hispid cotton rat is an agricultural pest noted for its destruction of cotton crops. It also devours sugarcane, alfalfa, and sweet potatoes and eats insects, birds' eggs, and carrion as well. With grizzled fur and a short, scaly tail, the cotton rat occurs mainly on farmlands of the Southeast. Although primarily nocturnal, it is sometimes seen along roads during the day, where it quickly disappears into weeds, ditches, or its own well-made runways. One of the world's most prolific mammals, the cotton rat begins to breed at six weeks of age and produces several litters each year. Predators such as cats, hawks, and snakes, however, help control its population.

Cottontail

See Rabbit.

Cottonwood

Populus

Found in almost every region of the country, cottonwoods are named for the parachute of cottony down attached to each of their seeds. When the tiny fruits burst open in late spring, the seeds drift away by the millions and collect in fluffy white windrows. Favoring damp soils in low-lying areas, these fast-growing members of the willow family may add four to five feet to their height annually. They peak at an early age, however: cottonwoods begin to decline when about 75 years old, and very few live more than a century.

During its relatively short lifespan, the eastern cottonwood may reach a height of 150 feet. Though settlers in the East paid little attention to it, on the prairie, where it was often the only tree around, the eastern cottonwood was treasured by pioneers. In the Pacific Northwest the black cottonwood is the largest broad-leaved tree; old accounts describe specimens 225 feet tall, with trunks 8 feet in diameter.

Cougar

See Mountain lion.

Count (noun)

Bird Biology Avian Conservation term.

The act or process of enumerating. The number or sum total obtained by counting.

Countershading

An Animal Behavior term, this is used to describe an aspect of camouflage in which an Animal is paler colored in less brightly lit areas, usually the underside, so that it appears to be uniform and is less easily detected.

Cowbird

Molothrus

Named for their habit of feeding among grazing cattle, cowbirds are best known as opportunists that raid the nests of other birds-not to take eggs, but to leave them. Both the bronzed cowbird of the Southwest and the more widespread brown-headed cowbird lay their eggs in the nests of other songbirds, such as warblers, vireos, and flycatchers, and then abandon them to be raised by foster parents. While such behavior may seem easier than incubating eggs and feeding nestlings, brood parasitism is costly for both the cowbird and its victims. Many species thwart the cowbirds by removing their eggs, burying them beneath a new nest lining, or abandoning the nest altogether. As a result, female cowbirds must lay many more eggs than other birds do. And the cowbirds that do hatch crowd out and starve some of the rightful nestlings. Most experts believe that the cowbirds' nest parasitism accounts for the decline of such songbirds as the endangered Kirtland's warbler in Michigan and Bell's vireo in California.

Cowrie

Cypraea

Noted for their glossy shells, brilliant colors, and intriguing patterns, these handsome snails have long been prized by collectors. On Pacific islands, royalty once wore golden cowries as symbols of rank. Although the cowries live mainly in tropical seas, a few species are found off our southern shores. The chestnut cowrie, about two inches long, inhabits rocky coasts and inlets in California, and the four-inch measled cowrie lives in bays and inlets in southern Florida.

Coyote

Canis latrans

"Ufe span, if lucky, about 13 years," one text says of the wide-ranging coyote, and certainly few animals have needed more luck to reach old age in the face of human persecution. For centuries coyotes have had an exaggerated reputation as ruthless predators of domestic livestock, especially sheep and poultry. Although studies show that these midsize wild dogs feed mainly on rabbits, ground squirrels, small rodents, and carrion, the truth is that they eat almost anything. In the South they have even been known to feed on watermelons and persimmons. Despite man's poisons, traps, and guns, coyotes have not merely survived; they have actually expanded their range as well. Their distinctive nocturnal yaps and howls now are heard from the suburbs of Los Angeles to the farmlands of New England. Coyotes mate in winter, and in spring the females give birth to litters of 4 to 10 tiny, helpless pups that grow with astonishing speed. Beginning at three weeks to take food provided by their fathers, they reach independence in the fall, when most disperse in search of home territories-and mates-of their own.

Coyness

An Animal Behavior term, this is used to describe the reluctance to mate, as is often found in newly formed pairs. In females, coyness may serve to ensure that the male is fully committed to her and will assist in care of young; in males it may ensure that young are his Rather than of any previous male.

Crab

Among the most familiar seashore creatures, crabs are easily identified by their broad backs, formidable pincers, and their habit of scuttling sideways on four pairs of walking legs. Adapted to a variety of habitats, they can be seen racing across the sand, burrowing into muddy salt marshes, and crawling across the sea floor. A few kinds live mainly on land, but all crabs must return to the water to reproduce. The eggs, which the females carry on their undersides, hatch into tiny free-swimming larvae that go through several molts before settling to the ocean bottom and developing into adults. Most crabs are scavengers and eat a variety of foods, which they seize in their pincers. Lady crabs and other swimming crabs have oarlike tips on their last pair of legs, enabling them to move swiftly through the water. The nocturnal ghost crabs run across beaches with astonishing speed, then burrow into sand above the high-tide line. Fiddler crabs are well known for the males' one enormously oversized pincer, which they brandish to court females and to fend off competing males. Blue crabs, one of the most important commercial species, are found in bays and estuaries all along the Atlantic coast. The soft-shelled crabs listed on seafood menus are usually blues; their shells are edible because the crabs have just molted.

Crab Spider

Masters of camouflage, some of the crab spiders can change their color to match the flowers on which they wait for passing prey. Once settled in, they grab any insect that comes close, poison it with their bite, and enjoy a meal. Uke their namesakes, crab spiders can easily and nimbly scuttle sideways. Although they do not spin webs, the females produce silken sacs to protect their eggs. They usually die, however, before the young emerge.

Cranberry

Vaccinium

Low, creeping vines with tough, wiry stems, cranberries flourish in bogs and other moist, acidic soils from Labrador to Alaska and south to North Carolina. Though Indians of the northeast relished the fruit, there is no proof that cranberries were served at the first Thanksgiving in 1621. By 1663, however, a recipe for cranberry sauce appeared in a Pilgrim cookbook, and in 1677 colonists sent 10 barrels of the crimson berries to King Charles II. Valued mainly for their fruits, cranberries nevertheless provide a colorful display over the seasons. In summer the vines are dotted with pretty pink flowers, which are followed in the fall by plump red berries; and in winter the leathery, oval leaves turn from dark green to blazing scarlet.

Crane

Grus

The two North American members of the ancient crane family are birds of open wetlands, plains, and prairies. The whooping crane, standing more than four feet tall, is the giant of our waders. It is also one of the most endangered of birds. In the 1940's the entire population of whoopers totaled fewer than two dozen. Now, however, with strict protection and careful management, the majestic white cranes are slowly increasing in number. Each spring the growing flock migrates from its winter home in Texas to its nesting ground in northern Canada. Sandhill cranes-regal, gray, and three to four feet tall-are more numerous than whoopers but also depend on shallow wetlands anri open prairies for survival. In an experiment begun in 1975, sandhill cranes that nest in Idaho have served as foster parents to eggs and young of captive-bred whooping cranes.

Cranes mate for life and may live for 30 years. Their remarkable calls can be heard a mile away, but even more compelling are the musical duets sung by mated pairs. The most striking aspect of crane courtship, though, is their dancing. Male and female bow low to each other and then bound high in the air, like bouncing balls, in the annual mating rite. Some native Americans copied the dance as part of their ceremonies. And one biologist, caring for a captive female whooper, induced her to lay an egg by repeatedly joining her in this courtship dance.

Crane fly

Tipula

Long-winged and long-legged, crane flies are often mistaken for huge mosquitoes. They are harmless, however; the adults feed only on nectar or, in some species, nothing at all. Walking and flying slowly and rather awkwardly, crane flies are usually found in dense vegetation or near water. They also are attracted to buildings, where, after dusk, clouds of them are frequently seen swarming about lights. The tough-skinned larvae, called leatherjackets, live in damp soil or shallow ponds and are often used as bait.

Crater

Formed at the summit of volcanoes or by the impact of meteors crashing into the earth from outer space, craters are steep-walled, circular depressions. Meteor Crater in Arizona, nearly a mile wide and 600 feet deep, is one of the best known of its type. The gaping hole was formed in prehistoric times when a meteor some 80 feet in diameter, traveling at more than 30,000 miles per hour, collided with the earth. Much more common are volcanic craters. Almost all volcanoes have small craters around their vents, caused by the slumping of molten lava at the end of an eruption. Later eruptions, such as the one that rocked Washington's Mount St. Helens in 1980, can destroy the summit and greatly enlarge the crater. Calderas, in contrast, are deep, broad basins often several miles in diameter, usually formed by the collapse of a volcanic cone into its empty magma chamber after an especially violent eruption.

Crayfish

Also called crawfish and, sometimes, crawdads, crayfish are freshwater crustaceans that look very much like miniature lobsters. Common in streams and quiet ponds, they grow to three or four inches in length. Four pairs of walking legs allow them to move in any direction. When danger threatens, however, they flex powerful abdominal muscles and dart abruptly backward, out of harm's way. Feeding on vegetation and a variety of small animals, crayfish in turn are prey for birds, turtles, raccoons, and otters. Some species live in deep burrows with a water-filled chamber at the end that serves as a refuge in times of drought. A few inhabit damp meadows and have earned a reputation as crop-eating pests. Crayfish are popular menu items, particularly in the Mississippi River basin. In Louisiana, residents and visitors alike savor such local favorites as crayfish bisque.

Creation

Biological Philosophy term. The idea is both philosophical and religious. Philosophically, the notion of an original creative act is not inherently antipathetic to evolution or to physics, nor is it refutable by science (see the conclusion of Hawking's Brief History of Time along with Harrison's Masks of the Universe). It is, however, a matter of belief, not science. Religiously, however, the Western notion of creation roots itself in the first two chapters of Genesis; and these accounts are, of course, incompatible with scientific accounts, though early scientists tried valiantly to reconcile scientific discoveries with a literal interpretation of Genesis.

Creationism or Special Creation

Biological Philosophy term. Creationism affirms that God created each form of life as it is, and denies the idea that the various forms of life evolved from earlier forms.

Creation Science

Biological Philosophy term. The claim that special creation is not merely a belief but a scientific hypothesis, a rival hypothesis to evolution.

Creosote bush

Larrea tridentata

The most common shrub of our southwestern deserts, the creosote bush is superbly adapted for survival. It sends out roots in two directions: a taproot reaches down to find deep hidden reserves of water, while a network of shallow roots quickly absorbs any rainfall at the surface. It also secretes an herbicide into the surrounding soil, killing any seedlings that might compete for moisture. A waxy coating on the leaves helps protect the creosote bush against dehydration, but in periods of extreme heat or drought it simply sheds its normally evergreen foliage, then sprouts new leaves when the weather becomes more moderate. And while some desert animals, such as the chuckwalla, thrive on the creosote bush's leaves and twigs, most mammals are warned off by an acrid odor that inspired the plant's nickname, stinkweed.

Crepuscular

An Animal Behavior term, this is used in describing Animal species that are active at dawn or dusk or both. Desert Animals are commonly crepuscular because hot and dry days and cold and dark nights are hostile.

Crevasse

An ever-present peril on glaciers, crevasses are gigantic vertical cracks that form in the slowly moving rivers of ice. Sometimes dozens of feet wide and more than ISO feet deep, they usually are caused by stresses that develop as the ice passes over obstructions or begins to descend steep slopes. Crossing a crevasse field on a glacier can be extremely hazardous, especially when a cover of snow hides the narrower gaps. Sometimes, however, the wider gaps can be crossed safely where wind-blown snow has formed bridges over the chasms.

Cricket

The subject of a great deal of superstition, crickets have been regarded as signaling both good fortune and bad. Having a cricket in the house brought good luck, while harming one was believed to cause all manner of woes. The most common of these familiar chirping, hopping insects are the black field cricket and the similar brown house cricket. The latter, an old-world import, thrives in American homes on food crumbs and even on bits of fabric. Smaller and pale green, the snowy tree cricket is known mostly by its sounds. Rubbing their wings together, the males sing in unison on summer nights and unwittingly tell us how warm it is: adding 40 to the number of times they chirp in 15 seconds yields the approximate temperature in degrees Fahrenheit.

Crinoid

Although they look like showy flowers of the sea, crinoids actually are invertebrate animals related to sand dollars and starfish. The two types of crinoids-sea lilies and feather starstrace their ancestry back to fossil forms that lived hundreds of millions of years ago. Sea lilies, the more flowerlike of the two, live atop long slender stalks that are permanently attached to the ocean floor, and use their feathery arms to strain food from the surrounding water. Feather stars, on the other hand, break free of their anchoring stalks as they mature, and use their arms to swim about in shallow water.

Critical habitat

Endangered and Threatened species term.

Specific geographic areas, whether occupied by listed species or not, that are determined to be essential for the conservation and management of listed species, and that have been formally described in the Federal Register.

Crocodilian

The closest living relatives of the long-extinct dinosaurs, crocodilians include alligators, caimans, crocodiles, and a single species of gavial. While the American alligator is quite plentiful in southeastern swamps and bayous, the American crocodile is an endangered species found only in southern Florida. In appearance, crocodiles differ from alligators in having narrower, more pointed snouts and bigger teeth that show more prominently even when the mouth is closed.

Crossbill

Loxia

Crossed at the tips, the distinctively twisted beaks of crossbills look at first glance like a handicap. In fact, they are delicate tools that serve very well for removing seeds from the cones of pines and other conifers. The birds use the crossed tips to pry the cone scales apart, then deftly extract the seeds with their tongue. Our two species of crossbills-white-winged and red-are primarily birds of northern forests. In years when cone crops fail, however, large flocks of cross bills often wander far beyond their normal range. Red crossbill males are brick-red, with dark wings and tail, and tend to favor pine seeds. Snowy wing bars highlight the rosier whitewinged crossbills, which prefer the seeds of spruces and hemlocks and often fly to the ground to open fallen cones.

Crow

Corvus

Bold, brash, mischievous, and black from beak to toe, crows are big, imposing birds with a three-foot wingspan. Adapting to a variety of habitats and resourceful in securing food, they also are extremely intelligent. Crows raiding cornfields, for example, have an uncanny ability to tell the difference between a farmer's gun and such harmless articles as brooms or sticks. Crows adopted as pets have actually learned to count and utter coherent phrases. And they solve the problem of cracking mollusks such as clams by carrying them into the air, then dropping them on rocks to smash the shells. Omnivorous in their eating habits, crows also devour eggs, worms, berries, insects, fish, grain, and animals killed on roadways. The familiar caw of the common crow is heard throughout the country in parks, farmlands, woods, and suburbs. Our other two crows, both slightly smaller than the common crow, are the fish crow of the Atlantic and Gulf coasts and the northwestern crow, which lives along the north Pacific coast from Washington to Alaska. More sociable than the common crow, they forage year-round in groups. Like all crows, they nest in pairs, but in winter they often gather by the thousands to roost.

Crustacean

Hard-shelled crabs scurrying along seashores, sowbugs living under logs, fairy shrimp swimming in temporary ponds---all are crustaceans. Like their relatives the insects, spiders, and scorpions, they have jointed legs and external skeletons, which they shed periodically as they grow.

The largest American crustacean is the Alaskan king crab. A record specimen measured six feet two inches from claw tip to claw tip. Although crustaceans are found in oceans from polar regions to tropical climes, they are not limited to the sea. Tiny brine shrimp, for instance, thrive in the ultrasalty waters of the Great Salt Lake, while others, such as crayfish, inhabit fresh water. A few specialized types live in the outflow of natural hot springs, and some, such as the land crabs of southern Florida, are terrestrial air-breathers.

Some of the crustaceans are pests. Crayfish riddle dikes and levees with their burrows; land crabs devour crop plants; and barnacles on the hull of a ship can cut its speed in half. But others, including lobsters, crabs, and shrimp, are valued human foods. And as a link in marine food chains, copepods and other tiny members of the class are swallowed up by a vast array of sea creatures, from arrow worms to whales.

Crypsis

An Animal Behavior term, see Camouflage.

Cryptic

Meaning colored to blend in, providing camouflage.

Crystal

Disparate as they may seem, salt, snowflakes, gemstones, metals, and sugar all have one thing in common: they are made up of crystals, as are most nonliving substances. Crystals are characterized by symmetrical atomic structures whose orderly patterns are repeated again and again, often yielding beautiful shapes. Some crystals, such as quartz, are large and conspicuous, but in most substances they are much too small to be seen with the naked eye.

Cuckoldry

An Animal Behavior term, this is used to describe the situation in which the female of a pair mates with males other than her partner. It is not infrequently observed, and mate-guarding by males is thought to have evolved as a device to avoid it and the possibility of the male rearing young which are not his own.

Cuckoo

Coccyzus

Unlike the brash character that leaps out of clocks to announce the hour, the cuckoos of North America are shy birds. Both the blackbilled cuckoo and the yellow-billed cuckoo prefer to hide in thickets at the edges of forests and orchards and are more likely to be heard than seen. (A third species, the mangrove cuckoo, lives only along the Florida coast.) Nest building is not one of the strong points of these slim, long-tailed birds; they raise their young on crudely assembled platforms of sticks and twigs. From the moment of hatching, the chicks are studded with stout quills that finally open into feathers just before the birds are ready to begin flying. The cuckoos' voracious appetite for insects, especially hairy caterpillars, makes them welcome allies in the fight against such pests as the gypsy moth. Tent caterpillars, which veil trees with their big cobweblike nests, are also a favored food. Yellow-billed cuckoos, in fact, have been known to consume more than 300 of these destructive larvae in a single meal.

Culture

The totality of ways of acting and thinking which a group acquires by experience and interpretation and then passes down by teaching and training. Roughly, culture is the learned human behavior which is passed on, as opposed to the instinctual behavior which evolves.

Cultural evolution

An Animal Behavior term, this is used to describe the changing of behavior as it passes from one geneRation to another through learning. Single individuals may learn new habits and, if these are copied by others, the change may spread and persist in the population without any genetic alteRation being involved.

Culture

An Animal Behavior term, this is used to describe a set of patterns of behavior which are reproduced geneRation after geneRation through learning, as well as the products of those behavior patterns, such as tools and works of art in Humans (see also Tradition).

Currant

Ribes

Valued for their tart, juicy berries, which are used in jams, jellies, and pies, currants are low to midsize shrubs that prefer cool, moist climates. Their arching branches, with lobed, maplelike leaves, bear clusters of tiny, bell-shaped yellow-green flowers that mature into shiny red, black, or amber fruits. Unfortunately, however, currants are host to a fungus called blister rust that attacks the eastern white pine and a number of other pines prized for their timber. Thus, while many species of wild currants are native to North America, they have been systematically eradicated from many areas.

Cusk-eel

Long, slender, and snaky, cusk-eels resemble true eels but have a pair of feelers (actually modified fins) under the chin. Although they are not common, cusk-eels are found in temperate and tropical seas around the world. The spotted cusk-eel, a dweller in deep water off the west coast, ranges from one to two feet in length; the striped cusk-eel of the east coast averages just six inches. To hide from predators, these shy and secretive fish back into rock crevices or burrow tail-first into sandy bottoms.

Cyclone

See Hurricane.

Cypress

Cupressus

Perched on rocky cliffs above the Pacific, their crowns flattened and their trunks contorted by driving winds, Monterey cypresses seem the perfect symbol of persistence. But their romantic beauty is rare indeed, for the trees' entire wild population is restricted to two groves in Carmel, California. In fact, all of our native cypresses, evergreens with scalelike foliage, woody cones, and fragrant wood-prefer dry, austere habitats in the Far West. The Modoc cypress, for example, flourishes in lava fields of the Siskiyou Mountains in northern California and Oregon, while the Arizona cypress is found only in arid canyons of the Southwest.

Cypress swamp

There's a sense of age and mystery about a Cypress Swamp as one meanders through a 100-foot canopy of trees that can reach an age of over 1,000 years. Such swamps were prevalent during the age of mammoths. But today, these swamps are populated with woodpeckers, raccoons, flying squirrels, owls, bee hives, and frogs. Reptiles are also common, including Snakes, Turtles and Alligators, but of course, no Dinosaurs remain.

Dabbling Ducks

Some ducks are not capable of completely submerging. Instead, they will merely tip their head down and their backside into the air. This allows them to feed on shallow plants.

Daddy long legs

Familiar to almost everyone, the daddy longlegs has a plump, oval body supported by eight long, threadlike legs. (The biggest of North America's 200 species boasts a three-inch leg span.) Although they are related to spiders, daddy longlegs lack silk glands and so spin no webs. They are not poisonous but can defend themselves by emitting a foul odor. Usually found in damp places, they feed on small insects, spiders, carrion, plant juices, and even each other. In the North most daddy longlegs hatch in the spring and die after the females lay their eggs in the fall. In the South they often hibernate. Because they mature in late summer and are often seen at harvest time, they are also known as harvestmen.

Daisy

Leucanthemum vulgare

Relatives of the florist's chrysanthemums, oxeye daisies are among the first wildflowers that most children learn to recognize. Their cheerful flower heads-bright yellow central disks encircled by haloes of white, petallike ray flowers-embellish fields and roadsides from coast to coast. Growing up to three feet tall, daisies have narrow, jagged leaves that when young are tender enough to be eaten in salads. When older, however, they become so pungent that even grazing cattle shun them.

Dall Sheep

Ovis dalli

Another species of North American wild sheep is called Dall or Dall’s Sheep or the Thinhorn Sheep. Dall sheep are smaller than Bighorns and have more slender horns. They live in Alaska and in the Yukon Territory and British Columbia provinces of Canada. They range in color from white in the northernmost part of their range to almost black in the southernmost part. Dark brown or black Dall sheep are also called Stone or Stone’s Sheep or Fannin Sheep.

Damselfish

Brilliantly colored and adorned with stripes, spots, and bars, damselfish are among the most striking of the small reef fish. Characterized by a single nostril in front of each eye (most fish have Damselfish, pugnacious reef dwellers, are known for launching aggressive attacks against much larger foes.) they are found in tropical and some temperate seas. Despite their name, these colorful fish are anything but delicate damsels. Daring warriors instead, they aggressively defend their home ground-a patch of kelp or coral or a crevice in the rocks- from other reef fish, spiny sea urchins, inquisitive barracudas, and even snorkelers and scuba divers. The sergeantmajor, named for its stripes, often travels in small platoons as far north as New England. Pacific coastal waters from southern California southward are the domain of the ferocious garibaldi. Not only does the bright orange male zealously defend its nest, but the nest site is often passed from one generation to the next

Damselfly

Flashing with brilliant metallic hues of green, blue, violet, and other colors as they dart through the summer air, damselflies are beautiful, slender-bodied insects. They often are mistaken for dragonflies, but while at rest, most damselflies fold their wings parallel to their body, while dragonflies hold them straight out. Like dragonflies, damselflies are found around water; they prey on mosquitoes and other small insects, which they trap in a cage formed by their legs. Damselfly nymphs are aquatic predators that usually creep along the bottom, but they can also scull through the water, using their three feathery gills as oars.

Dandelion

Taraxacum officinale

Though gardeners might find it difficult to believe, North America used to be almost entirely free of dandelions. Once it had been imported by early colonists, however, the familiar yellow-flowered weed proceeded to do some colonizing on its own, its downy seeds floating off and eventually taking root across the continent. Fecundity is one reason for the dandelion's success. Its flower heads contain as many as 200 individual florets, each of which sets seed without need for pollination. The blossoms, moreover, release ethylene gas in the late afternoon, which poisons competing plants. And the dandelion's hollow stem contains a bitter white sap that effectively discourages grazing animals.

Darter

Little minnowlike fish that range from one to nine inches in length, darters are named for their habit of darting swiftly from one resting place to the next. More than lOO species live in streams and lakes east of the Rockies, where they feed on a variety of small aquatic animals. Many of the darters are brightly colored, with the males' hues becoming particularly intense during the breeding season. Common species include the widespread]ohnny darter; the sand darter, which burrows into sandy stream bottoms and leaves only its eyes and snout exposed to detect prey; and the celebrated snail darter, which made news in the 1970's when concern over destruction of its habitat delayed completion of a dam.

Dayflower

Commelina

Thriving in shady dooryards, roadsides, and woodland clearings, dayflowers furnish a pretty show of three-petaled blue flowers from May to October. When the blooms open, the two larger, upper petals arch back to expose the nectar and invite visits from pollinating bees. After a few hours, the petals wilt, wrapping a moist blanket around the flower's pistil and stamens. This allows for self-pollination, so that even without the help of bees, fertile seed is assured.

Daylily

Hemerocallis

Roadside wildflowers of beauty and elegance, daylilies are hardy perennials that long ago escaped from cultivation. Both the orange and the yellow daylily, the latter lemon-scented, bloom in loose clusters atop four-foot stalks. Though each trumpet-shaped flower lives only a day, as the name suggests, the plants produce a succession of blossoms over several weeks. Resistant to insects and disease, daylilies also are extremely resilient: their fleshy, fibrous roots easily survived the long ocean voyages of the settlers who introduced them, and they have since become established in the wild as far west as Texas.

Death camas

Zigadenus

Aptly named, the death camases are poisonous in every part. They can easily be distinguished from their edible relatives, the true camases, when in bloom. On death camases, the spikes of small, six-pointed flowers are greenish yellow, white, or bronze, while most of the true camases have blue flowers. In early spring, however, the differences are not so apparent, since all are simply tufts of grasslike leaves. Indians, who used to gather camas bulbs for food, occasionally made fatal mistakes in identification. Even today, the death camases sometimes poison sheep and cattle on the western mountains and plains.

Deceit

An Animal Behavior term, see Cheating.

Decomposer

When a plant or animal dies, hosts of other organisms feed on its remains. The most numerous of these decomposers are bacteria and fungi, indispensible recyclers that break down organic compounds into simpler components and so return vital nutrients to the environment. A host of small animals, from earthworms to insects, also feed on the remains. The wood-gnawing larvae of bark beetles, for instance, tunnel beneath the bark of rotting logs, where they in turn become hosts to the parasitic larvae of tiny wasps. Termites, too, may consume the wood but must rely on microscopic protozoans in their bodies to actually digest the fibers. Thus a single rotting log on the forest floor can be a thriving metropolis of interrelated life.

Deciduous

A woody plant that sheds its leaves in winter.

Deciduous Forest

Dominated by lofty and elegant broad-leaved trees that shed their foliage in autumn, deciduous (as opposed to evergreen) forests flourish in moist, rich soils over much of the eastern United States. Oaks, maples, beeches, birches, and other tall trees, their crowns merging into a continuous canopy, spread their leaves in the sunlight to manufacture food. Squirrels, hawks, and owls nest in the treetops, insects feed on the leaves, and birds in turn feed on the insects. Below the canopy is an understory of shade-tolerant trees. Deer wander among the low-growing ferns and scattered shrubs on the sun-dappled forest floor, woodcocks probe the soil for worms, and bears search for wild berries. The forest floor is also a place where decaying logs and leaves are broken down by insects, worms, fungi, and bacteria, renewing the soil by releasing vital nutrients. With the cool of autumn, the green leaves tum to yellow, orange, and red, and for a short time, especially in New England, the forests are ablaze with colors that rival those of the most dazzling flowers. By winter, most of the leaves have fallen to the forest floor, leaving bare branches silhouetted against the sky. In spring, before the canopy of leaves has had a chance to fill in again, the sun-drenched forest floor is carpeted with a tapestry of wildflowers.

Deciduous forest biome

Deciduous forests can be found in the eastern half of North America. The average annual temperature in a deciduous forest is 50° F. The average rainfall is 30 to 60 inches a year.

In deciduous forests there are five different zones. The first zone is the Tree Stratum zone. The Tree Stratum zone contains such trees as oak, beech, maple, chestnut hickory, elm, basswood, linden, walnut, and sweet gum trees. This zone has height ranges between 60 feet and 100 feet.

The small tree and sapling zone is the second zone. This zone has young, and short trees. The third zone is called the shrub zone. Some of the shrubs in this zone are rhododendrons, azaleas, mountain laurel, and huckleberries. The Herb zone is the fourth zone. It contains short plants such as herbal plants. The final zone is the Ground zone. It contains lichen, club mosses, and true mosses.

The deciduous forest has four distinct seasons, spring, summer, autumn, and winter. In the autumn the leaves change color. During the winter months the trees lose their leaves.

The animals adapt to the climate by hibernating in the winter and living off the land in the other three seasons. The animals have adapted to the land by trying the plants in the forest to see if they are good to eat for a good supply of food. Also the trees provide shelter for them. Animal use the trees for food and a water sources. Most of the animals are camouflaged to look like the ground.

The plants have adapted to the forests by leaning toward the sun. Soaking up the nutrients in the ground is also a way of adaptation.

A lot of deciduous forests have lost land to farms and towns. Although people are trying to protect the forests some poachers are trying to kill the animals in the forests. The animals are losing their homes because of people building their homes.

Deer

Odocoileus

Our only animals with antlers, North America's deer include three giants-moose, caribou, and wapiti, or elk. The most widespread and abundant members of the family, however, are the alert, elegant bucks, graceful does, and dappled fawns of the white-tailed and the mule deer. Especially common throughout the East, the delicate white-tailed, or Virginia, deer prefers woodland edges but can also be found in many suburban areas. Up to 3V2 feet tall and weighing as much as 250 pounds, it is a fleet, elusive creature that, when frightened, flashes the white underside of its tail like a banner. The stockier, long-eared mule deer lives in the West on forested mountain slopes as well as in deserts and chaparral. The black-tailed deer of the Northwest is a subspecies of the mule deer. Both white-tails and mule deer browse by day and on moonlit nights on the buds and twigs of trees, feeding on tender grass, berries, and acorns when they are available. During hard winters they barely subsist on the meager food that is available, and starvation is common. In fall, the antlered males battle other bucks for mates. Some seven months later, first-time mothers generally give birth to a single fawn, while older does commonly bear twins. The young have spotted coats that provide camouflage when they crouch motionless on the forest floor or in tall grass. And they are scentless, which further protects them from predators.

Deer family

Hoofed Mammals that have antlers. They are ruminants and have no upper incisors. These include the Deer, Elk, Moose, and Caribou.

Deer mouse

See White-footed mouse.

Deep time

Biological Philosophy term. The discovery that the universe has been around for more than the few thousand years recorded in the Bible, that it has been in existence for billions of years.

Deforestation

Removal of trees from a forested area without adequate replanting or natural regeneration.

Delayed Implantation

Many animals, in particular the weasels and bears experience a delay in the reproductive process. After mating, the fertilized embryo may float freely in the uterus for up to six months without significant development. At the end of this period (which varies with each species), if the female is healthy, the egg will implant and begin to develop. However, if she is in poor condition, the egg may simply be reabsorbed by the body. This allows more control over population than other animals for whom pregnancy is a one-way street.

Delist

Endangered and Threatened species term.

The process of removing an animal or plant from the list of Endangered and Threatened Wildlife and Plants.

Delta

Formed at the mouths of rivers or streams, where the water slows and drops its burden of sand, silt, and clay, deltas are often triangular in shape and take their name from their resemblance to the Greek letter delta. Not all are wedge shaped, however: some are rounded, and some, like the Mississippi River's, are pronged like bird feet. The size and shape depend on the size of the river, the amount of sediment it carries, and the currents where it empties. The Mississippi River, with a delta that covers hundreds of square miles, dumps more than 5 million tons of sediment each year into the Gulf of Mexico, extending the delta another 200 feet into the Gulf annually. Other notable examples include the Red River delta, formed where the river flows into Lake Winnipeg, and the Colorado River's delta in man-made Lake Mead.

Deer mouse

See White-footed mouse.

Delta

Formed at the mouths of rivers or streams, where the water slows and drops its burden of sand, silt, and clay, deltas are often triangular in shape and take their name from their resemblance to the Greek letter delta. Not all are wedge shaped, however: some are rounded, and some, like the Mississippi River's, are pronged like bird feet. The size and shape depend on the size of the river, the amount of sediment it carries, and the currents where it empties. The Mississippi River, with a delta that covers hundreds of square miles, dumps more than 5 million tons of sediment each year into the Gulf of Mexico, extending the delta another 200 feet into the Gulf annually. Other notable examples include the Red River delta, formed where the river flows into Lake Winnipeg, and the Colorado River's delta in man-made Lake Mead.

Demographic parameters

Bird Biology Avian Conservation term.

Fecundity and mortality parameters used to predict population changes, such as number of eggs laid per clutch, the frequency at which clutches are laid, the survivorship of eggs and young in the nest and to the age at first reproduction, and the subsequent survival of the adults throughout their lifetime.

Density

The number of units (e.g., individuals, pairs, groups, nests) per unit area.

Density-dependent

Having influence on individuals in a population in a manner that varies with the degree of crowding in the population.

Density-independent

Having influence on individuals in a population in a manner that does not vary with the degree of crowding in the population.

Desert

A Hot and Dry Desert is, as you can tell from the name, hot and dry. Most Hot and Dry Deserts don't have very many plants. They do have some low down plants though. The only animals they have that can survive have the ability to burrow under ground. This is because they would not be able to live in the hot sun and heat. They only come out in the night when it is a little cooler.

A Cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and Dry Deserts.

Deserts cover about one fifth of the Earth's land surface. Most Hot and Dry Deserts are near the Tropic of Cancer or the Tropic of Capricorn. Cold Deserts are near the Arctic part of the world.

Hot and Dry Deserts temperature ranges from a low of 70 to 80 degrees in the summer during the day and goes upward from there. The extreme maximum temperature for Hot Desert ranges from 110 to 130 degrees. Cold Deserts temperature in winter ranges from 30 to 40 degrees and in the summer it ranges from 70 to 80 degrees.

The precipitation in Hot and Dry Deserts and the precipitation in Cold Deserts is different. Hot and Dry Deserts usually have very little rainfall and/or concentrated rainfall in short periods between long rainless periods. This averages out to under a few inches a year. Cold Deserts usually have lots of snow. They also have rain around spring. This averages out to as much as 10 inches of rain or more in a year.

Hot and Dry Deserts are warm throughout the fall and spring seasons and very hot during the summer. the winters usually have very little if any rainfall. Cold Deserts have quite a bit of snow during winter. The summer and the beginning of the spring are barely warm enough for a few lichens, grasses and mosses to grow.

Hot and Dry Deserts vegetation is very rare. Plants are almost all ground-hugging shrubs and short woody trees. All of the leaves are replete (packed with nutrients). Some examples of these kinds of plant are Turpentine Bush, Prickly Pears, and Brittle Bush. For all of these plants to survive they have to have adaptations. Some of the adaptations in this case are the ability to store water for long periods of time and the ability to stand the hot weather.

Cold Desert's plants are scattered. In areas with little shade,about 10 percent of the ground is covered with plants. In some areas of sagebrush it reaches 85 percent. The height of scrub varies from a few inches to several feet at the most. All plants are either deciduous and more or less contain spiny leaves.

Hot and Dry Deserts animals include small nocturnal (only active at night) carnivores. There are also insects, arachnids, reptiles, and birds. Some common examples of these animals are lizards and snakes. Cold Deserts have animals like Antelope, Ground Squirrels, Jack Rabbits, and Kangaroo Rats.

Desert pavement

Long before humans were paving roads, wind and water were at work paving parts of deserts with mosaiclike expanses of closely packed rock fragments known as desert pavement. These barren, windswept areas result where finer particles of sand and soil have been carried away by erosion, leaving the surface covered with a solid armor of rocks. Though we usually think of deserts as sandy places, rocky areas sheathed with desert pavement, such as those found in parts of California's Death Valley, are actually far more common than sand.

Desert poppy

Kallstroemia grandiflora

In late summer the desert poppy spreads brilliant coverlets of bloom over dry, sandy flats and slopes from western Texas to southern California. Bright orange and bowl-shaped, the fivepetaled blossoms are two inches across and grow on sprawling hairy stems. Later in the season the handsome flowers are followed by seedfilled fruits with long beaks and spiny, swollen bodies that look like miniature replicas of medieval maces. Though not poppies at all, these tough annual wildflowers are also known as Arizona poppies and summer poppies.

Desert pavement

Long before humans were paving roads, wind and water were at work paving parts of deserts with mosaiclike expanses of closely packed rock fragments known as desert pavement. These barren, windswept areas result where finer particles of sand and soil have been carried away by erosion, leaving the surface covered with a solid armor of rocks. Though we usually think of deserts as sandy places, rocky areas sheathed with desert pavement, such as those found in parts of California's Death Valley, are actually far more common than sand.

Desert poppy

Kallstroemia grandiflora

In late summer the desert poppy spreads brilliant coverlets of bloom over dry, sandy flats and slopes from western Texas to southern California. Bright orange and bowl-shaped, the fivepetaled blossoms are two inches across and grow on sprawling hairy stems. Later in the season the handsome flowers are followed by seedfilled fruits with long beaks and spiny, swollen bodies that look like miniature replicas of medieval maces. Though not poppies at all, these tough annual wildflowers are also known as Arizona poppies and summer poppies.

Desertion

An Animal Behavior term, this is used to describe the situation in which one partner leaves parental care to the other at some stage after mating. Whole species may show the same pattern: eg female alone caring (Ducks) or male alone (someFishes). In other cases, desertion occurs occasionally where the deserted partner can rear young alone and the deserter can find a new mate. The term is also applied to desertion of offspring by adults which may occur after disturbance or in adverse conditions.

Design

Biological Philosophy term. An argument for the existence of God. Here, for instance, is Thomas Jefferson's version: "I hold (without appeal to revelation) that when we take a view of the universe, in its parts general or particular, it is impossible for the human mind not to perceive and feel a conviction of design, consummate skill, and indefinite power in every atom of its composition. The movement of the heavenly bodies, so exactly held in their course by the balance of centrifugal and centripetal forces, the structure of our earth itself, with its distribution of lands, waters and atmosphere, animal and vegetable bodies, examined in all their minutest particles, insects mere atoms of life, yet as perfectly organized as man or mammoth, the mineral substances, their generation and uses, it is impossible, I say, for the human mind not to believe that there is, in all this, design, cause and effect, up to an ultimate cause, a fabricator of all things from matter and motion, their preserver and regulator while permitted to exist in their present forms, and their regenerator into new and other forms." (Letter to John Adams)

Detectability

Bird Biology Avian Conservation term.

A measure of the conspicuousness of a species equal to the proportion of actual units (individuals, territorial males, etc.) observed on a given area.

Detection distance

Bird Biology Avian Conservation term.

The distance from the observer at which the individual or cluster of individuals is seen or heard (the radius in point counts and the lateral or perpendicular distance in transect counts).

Devil's walking stick

Aralia spinosa

Sometimes growing as a 40-foot tree, the devil's walking stick more often has just a single stem some 15 feet tall, topped by a parasol of huge, twice-divided leaves. Up to three feet long, they are the biggest leaves borne by any native shrub or tree. Also known as Hercules' club, the devil's walking stick is armed with a fearsome array of thorns, which even bristle from the leaf stalks. In summer the plant's forbidding aspect is softened by huge clusters of little greenish flowers that, by autumn, turn into small black berries. Ranging from New York to east Texas, the deviI's walking stick often forms dense thickets along streambanks and other low-lying areas. The devil's walking stick, despite its fearsome armament of spines, is sometimes eaten by hungry white-tailed deer. The small, five-seeded black berries, however, are ignored by all but a few mammals and birds.

Dew

When the sun goes down at the end of the day, objects near the ground begin to cool off and chill the warmer air that surrounds them. As the air cools, it becomes more saturated with the water vapor it contains, because cool air cannot hold as much moisture as warm air can. When the air reaches the temperature at which it is completely saturated with water vapor-its dew point-some of the vapor condenses as dew, glistening drops of water that appear on grasses, flower petals, spiderwebs, and other outdoor surfaces. (If the dew point is below freezing, the excess moisture freezes directly onto surfaces and is called frost.) Most likely to form on calm, clear nights, dew is an important source of moisture for many desert plants.

Dewberry

See Blackberry.

Dewlap

A pendant of hair-covered skin that hangs from under the throat of an Animal, e.g., the Moose.

Dialect

An Animal Behavior term, this is used to describe the variation of social signals within a species from one locality to another. Described for vocalizations of Birds and Frogs, and for the waggle dance of the HoneyBee. The term is sometimes restricted to cases where variation shows sharp boundaries between populations giving a mosaic of signal forms.

Diamond

The hardest of all natural substances, diamonds are formed from carbon that was dissolved in molten rock and cooled under enormous pressure. Looking like glassy, irregular pebbles, they can be cut and polished to produce gems. Most, however, are not of gem quality and are used instead as industrial abrasives. The only Significant diamond field in the United States is in Arkansas, but diamonds scattered by glaciers and streams have been found near the Great Lakes, in the Appalachians, and in California.

Diatom

Among the most abundant of all living things, diatoms are so tiny that as many as 20 million of these one-celled plants can live in a single quart of seawater. Unlike other algae, they have shelllike cell walls made of silica and come in a bewildering variety of shapes-round, square, needlelike, triangular, starlike, and more.

Golden brown in color, diatoms live in both salt and fresh water. They sometimes form slimy films or jellylike lumps on underwater stones and sticks, but most float free in the plankton. Key links in aquatic and marine food chains, they are eaten in countless numbers by planktonic animals that are in turn the food of larger creatures of the sea. After death the empty shells of diatoms accumulate in deposits of diatomaceous earth, valued as an ingredient in scouring powder and other abrasives; as a filter; and as a filler in paints, plastics, and other products.

Dinosaur

Dominating the earth for 140 million years, dinosaurs were the largest land animals that ever lived. The earliest of these giant reptiles appeared more than 200 million years ago, and the last of them mysteriously disappeared some 65 million years ago. In North America, dinosaurs lived mainly on the plains and badlands just east of the present-day Rocky Mountains, in the Southwest, and on the coastal plain between the Appalachian Mountains and the sea. Among the hundreds of species that flourished here were the fearsome three-horned triceratops; the stegosaur, with a deadly spiked tail used in selfdefense; and the 75-foot, 30-ton brontosaur ("thunder lizard"). The largest dinosaur, the seismosaur ("earthquake lizard"), was up to 120 feet long and weighed perhaps 100 tons. Its fossil remains were discovered by hikers in New Mexico in 1986. Preying on these herbivores were a variety of awesome carnivores, notably the Tyrannosaurus rex ("tyrant lizard king"), which was 40 feet long, 18 feet high at the hip, and had a huge head and a mouth filled with 6-inch-long daggerlike teeth.

Dipper

Cinclus mexicanus

Stocky, gray, short-tailed songbirds that favor waterfalls and cold rushing mountain streams of the Far West, American dippers earn their living in an extraordinary way. Undaunted even by water too turbulent for humans to stand in, they fearlessly plunge in and pump their wings to reach the bottom, where they stride along the streambed in search of food. Small fish and insect larvae are their main prey.

Also known as water ouzels, dippers have big feet and thick plumage that is waterproofed by oil from large preen glands. Flaps over the nostrils, and transparent membranes that close over the eyes complete their diving outfits. The dippers' fluid song, often delivered from streamside boulders, can be heard even over the roar of rushing water. The birds always build their domed nests near waterways. Some even raise their families behind the curtains of waterfalls-one reason why the young must be accomplished swimmers when they leave the nest.

Direct competition

Bird Biology Avian Conservation term.

The exclusion of individuals from resources by aggressive behavior or use of toxins.

Disc florets

Small flowers found at the centre of the inflorescence of members of the daisy family.

Discrimination

An Animal Behavior term, this is used to describe the ability of an Animal to distinguish between two stimuli. Thus, Gulls prefer to sit on brown egg models Rather than on red ones and so must be able to distinguish between them. Many psychological studies have examined the processes of discrimination learning whereby Animals can be trained to make such distinctions.

Disease (Wildlife)

Bird Biology Avian Conservation. Birds, like any animals, are subject to illness, and the migratory nature of many species makes it hard to control the spread of contagious diseases, such as avian cholera. Avian botulism, which is contracted by eating poisoned maggots, occurs naturally and is a leading cause of bird death, especially in migratory waterfowl.

Dispersal

The movement of organisms away from the place of birth or from centers of population density.

Dispersion

The pattern of spacing of individuals in a population. The nonaccidental movement of individuals into or out of an area or population, typically a movement over a relatively short distance and of a regular nature.

Displacement activity

An Animal Behavior term, this is used to describe seemingly irrelevAnt behavior, such as grooming or nest building, sometimes shown by courting or fighting Animals. It is thought to be shown where more relevAnt behaviors are thwarted or in conflict. Such actions are often hurried or incomplete and some are considered to have been the original behavior from which certain Displays evolved.

Display

An Animal Behavior term, this is used to describe movement pattern used in communiCation. These are often striking, stereotyped and species-specific, especially during courtship and aggressive behavior. Displays may also function between species (see also Distraction Display).

Disruptive coloration

An Animal Behavior term, this is used to describe color patterns which break up the outline of an Animal and other features of its body so that it is very hard to pick out when motionless.

Distraction display

An Animal Behavior term, this is used to describe a Display with which Mother Birds lead predators away from their broods by feigning injury.

Distinct population segment

If it satisfies the criteria specified in the February 7, 1996, Federal Register, pages 4722-4725, a portion of a vertebrate (i.e., animals with a backbone) species or subspecies can be listed. The criteria require it to be readily separable from the rest of its species and to be biologically and ecologically significant. Such a portion of a species or subspecies is called a distinct population segment.

Disturbance

Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment.

Diurnal

Meaning active during daylight hours.

Diversity

Bird Biology Avian Conservation term.

Typically used in relation to species, a single index that incorporates the number of species and relative abundances of species (evenness). For example, a collection is said to have high diversity if it has many species and their abundances are relatively even. There are many types of diversity:

Point diversity--for a small or microhabitat sample within a community regarded as homogeneous

Pattern diversity--as change between parts of the internal pattern of a community

Alpha diversity--for a sample representing a community regarded as homogeneous (despite its internal pattern)

Beta diversity--as change along an environmental gradient or among the different communities of a landscape

Gamma diversity--for a landscape or set of samples including more than one kind of community

Delta diversity--as change along climatic gradients or among geographic areas

Epsilon diversity--for a broader geographic area, including differing landscapes

Diving Ducks

Some waterfowl are able to dive completely below the surface, allowing them to feed in much deeper water than dabbling ducks.

Dobsonfly

Long, fearsome-looking insects with a five-inch wingspan, male dobsonflies have a daunting pair of jaws: an inch long on some species and gracefully curved, they look like crossed sabers. (The females' jaws are much smaller.) During their brief two-week existence as adults, these fluttery fliers sometimes are seen congregating around outdoor lights. After mating, they lay waxy clusters of eggs on leaves or branches above rapid streams. When the larvae hatch, they drop into the water and spend two years or so as ravenous aquatic predators, lurking under stones and gobbling up small prey. Known as hellgrammites, dobsonfly larvae can inflict painful bites on swimmers. They are, however, relished by bass and prized by anglers as bait.

Dock

Rumex

Found on roadsides and in fields and gardens from coast to coast, docks are ubiquitous members of the buckwheat family. Thanks to long, penetrating taproots, they also are among the most persistent. Leaves vary with the species, but most docks look alike in flower and seed. In June they send up tall stems topped with spikes of small greenish flowers, which by September yield an abundant crop of reddish-brown, threesided fruits. All parts of the plants are avidly consumed by wildlife.

Dodder

Cuscuta

A threadlike parasite that twines around other plants, dodder is a nuisance that sucks the juices from ornamentals and valuable crop plants. Each seed sends up a thin stem that attaches itself to a nearby plant, penetrating the host's tissue and drinking in its sap. Dodder's own roots then wither, leaving the parasite with no attachment to the soil. Its leafless stems are light orange, lacking the chlorophyll that enables other plants to make their own food. Dodder does bloom like a normal plant, however, bearing dense clusters of tiny, bell-shaped, white or yellow flowers. Its seeds can lie dormant for five years, but once they sprout, each can produce a half mile of coiling stems in just four months.

Dogbane

Apocynum

Despite their sinister name, our several species of dogbanes are of little threat to dogs. Nor, despite their poisonous milky sap, are they any threat to grazers: the juice is so bitter that animals generally avoid the plants. From June to September, all the dogbanes are arrayed with clusters of pink or whitish flowers. The tallest species, a five-foot plant sometimes called Indian hemp, has especially stringy bark that Indians used for making rope and fishnets.

Dogtooth violet

Erythronium

The dozen or more wildflowers known as dogtooth violets all are members of the lily family and are among the first to bloom in spring. In the East the common species is the trout lily, named for its mottled green leaves. Often growing in large patches, each plant bears a single yellow bloom atop a four- to eight-inch stem. Of the several western dogtooth violets, one of the best known is the glacier lily, a white-flowered species found near snow fields.

Dogwood

Comus

Virginia and North Carolina both claim the dogwood as their state flower, but in fact the white spring blooms beloved from Maine to Texas are not flowers at all. Their four notched "petals" are actually bracts, modified leaves that surround the real flowers-the cluster of tiny greenishyellow blossoms at their center.

Dogwood is useful and lovely-the bark was substituted for quinine during the Civil War. Seldom exceeding 30 feet in height, the flowering dogwood of the East is overshadowed by the Pacific dogwood of the West, which grows up to 60 feet tall. Four to six white bracts encircle its flower clusters, and it sometimes blooms twice a year. Both trees, unfortunately, are susceptible to a fungus disease that in recent years has caused an epidemic of deaths among these beautiful ornamentals. Well known-and easily recognized-among the smaller species is the red osier dogwood, a shrub with blood-red bark that adds a welcome note of color to winter landscapes. Another, silky dogwood, is a spreading species with purplish twigs that favors streambanks and similar moist places. Notable berry producers, the dogwoods rank high among trees and shrubs as a source of food for wildlife.

Dolomite

Composed of calcium carbonate, dolomite is nearly identical to limestone-with one crucial difference. It contains magnesium, which makes it harder and less soluble than limestone and therefore more resistant to weathering. Most dolomite was formed when magnesium-rich water seeped into preexisting limestone and replaced some of the rock's calcium with magnesium. Dolomite is used as a building stone, a lining for furnaces, and in smelting.

Dolphin

Often seen cavorting off the bows of moving ships, schools of dolphins move in graceful arcs as they leap above the waves. These playful, intelligent mammals are actually small, toothed whales, whose beaklike snouts distinguish them from their blunt-nosed relatives, the porpoises. With a highly varied repertoire of whistles, clicks, and chirps, dolphins can signal to each other and even carry on conversations. They also produce ultrasonic sounds, which they use for navigation and locating prey. Using their teeth to capture and hold prey rather than to chew it, dolphins feed on fish and squid, swallowing them whole. Like other whales, dolphins breathe through a blowhole on the back and sleep while floating near the surface. Found off both the Atlantic and Pacific coasts, the eight-foot common dolphin has a black back, white belly, and yellowish stripes on its sides. The larger bottle-nosed dolphin is 9 to 12 feet long and mostly gray in color. Famous for its ability as a performer, the bottle-nosed dolphin thrives in captivity, is easily trained, and has made innumerable appearances in films and aquarium shows.

Dolphinfish

Coryphaena hippurus

Though no relation to the acrobatic marine mammals known as dolphins, dolphinfish also are well known for their agile antics: lightning speed, dramatic leaps, and ferocious fighting ability make them a favorite with deep-sea fishermen. Unmistakable in appearance, dolphinfish are up to 6 V2 feet long, with a dorsal fin that tapers all the way from their blunt head to their forked tail. The fish also are brilliantly colored, with deep blue and green on the back and bright golden flanks (which no doubt inspired their other name, dorado). Roaming in schools, dolphinfish feed on squid, crustaceans, and especially, flying fish, which they often pursue by leaping above the waves.

Dominance

An Animal Behavior term, this is used to describe the situation in which one Animal dominates another in fights or in access to resources such as sitting positions, food and mates. DominAnts are often older or stronger, but fighting may not be involved in encounters because subordinates frequently defer. In some social groups, relationships may be consistent and clear enough for Animals to be placed in a linear dominance hierarchy in which each is dominated by those above it and dominates those below.

Dorsal

The upper surface.

Dorsal fin

One or more fins along the backbone of a fish, dolphin or whale.

Douglas fir

Pseudotsuga

Towering, majestic trees that sometimes reach heights of more than 300 feet, Douglas firs are exceeded in size only by the redwoods and giant sequoias. The largest specimen on record stood 385 feet tall and had a trunk 15 feet thick. On the tallest trees, the trunks soar straight up for 100 feet or more and are crowned by a compact pyramid of branches covered with flattened needles and pendulous cones. In 1825, botanist David Douglas, for whom the tree is named, failed in his first attempt to collect seeds because his shotgun would not shoot high enough to dislodge a cone. Unmistakable in appearance, the cones have three-pointed, ribbonlike bracts projecting from between their scales. Though the biggest trees are found in coastal forests from British Columbia to northern California, Douglas firs range through much of the West. Prized as ornamentals and for Christmas trees, they also are one of our most valuable timber trees.

Dove

Known for their gentle, cooing calls, doves have been symbols of peace and love since ancient times. Stocky, small-headed, and usually brown or gray, they scuttle along on short legs with their heads bobbing back and forth. Although there is no technical distinction between doves and pigeons, doves tend to be smaller, more graceful birds with pointed tails, while pigeons are larger and have fan-shaped tails. Doves nest on flimsy platforms of twigs and usually lay two pale, unmarked eggs. The newly hatched young are fed pigeon milk, a substance that looks like cottage cheese and is produced in the parents' crops. Mature doves feed mainly on seeds and fruit and are among the few birds that can drink without lifting their heads to let the water run down their throats. The most widespread species is the mourning dove, whose repeated coos add a poignant, mournful note to forests, deserts, suburbs, and even cities from coast to coast. Because of it abundance and fast flight, the mourning dove is a popular game bird in many states. So is the white-winged dove, which lives in the Southwest. The sparrow-sized common ground-dove is found in southern grasslands, and the similar Inca dove prefers to nest in deserts.

Dragonfly

Quick and agile fliers, dragonflies are long, slender insects equipped with two pairs of gauzelike wings that shimmer in the sunlight. Although our largest species has a wingspan of nearly six inches, fossils reveal that some of their ancient ancestors were five times that size. Dragonflies are usually seen hovering over ponds and quiet streams, where they hunt for mosquitoes and other insects. Gathering their legs together to form a sort of basket, they scoop up their victims as they dart through the air. Even as aquatic nymphs, immature dragonflies are accomplished predators. Their hinged lower jaws, armed with sharp hooks at the end, can shoot out with lightning speed to snatch tadpoles, small fish, and insects. After one or more years, the homely nymphs emerge from the water and begin their lives as graceful, winged adults.

Drinking Water

Water that is pure enough for drinking.

Drive

An Animal Behavior term, this is a psychological term applied to supposed moving forces underlying the appearance of behavior. For example, the hunger drive, sex drive and social drive. The term has fallen from use as the causes of behavior have Been analyzed in more detail and different factors have Been found to affect different aspects of behavior without the need for motive forces affecting each of them to be postulated.

Drizzle

Associated with gloomy days and low-lying clouds, the form of precipitation we call drizzle is neither mist nor rain but something in between. It is made up of water droplets that are

just large enough to drift slowly downward. They are not so small that they float in the air as do the tiny particles of mist or fog. Nor are they so large and heavy that they fall rapidly like rain. And unlike rain, which is associated with high, turbulent clouds that tend to pass quickly overhead, drizzle usually continues to fall over longer periods of time.

Drought

When the amount of precipitation in a region drops far below its normal level over an extended period of time, the resultant shortage of moisture is called a drought. In their severest form, droughts can cause a succession of calamities and take an enormous toll on life, land, and the economy. Streams and reservoirs dry up; crops wither and perish; animals starve or die of thirst; the soil turns to dust and is carried away by the wind; and grass and forest fires rage out of control. In the 1930's, for example, the Great Plains were devastated by one of the worst droughts in history. Crops failed, much of the land was ruined, and families were forced to abandon their homes forever.

Drum

Also known as croakers, drums are named for the low-pitched sounds they make by contracting muscles next to the swim bladder. The family includes about 160 species of mostly oceanic fish, though not all of them croak, because not all are equipped with the swim bladder that serves to amplify the sound. The various species range from 1 to 100 pounds in weight, but all have in common a conspicuous notch dividing the dorsal fin into two parts. Found mostly in shallow coastal waters, the drums are popular commercial and sport fish. Millions of red drums, or channel bass, are caught off Florida every year, and black drums and spotted seatrout are sought from New England to the Rio Grande. Off the west coast, the white seabass, up to four feet long, also is prized by fishermen. Other drums include the weakfish and kingfish, found in the Atlantic, and the freshwater drum of the central states.

Drumlin

Relics of the Ice Age, drumlins are long, low, oval-shaped hills composed of glacially deposited rock debris. Molded into their characteristic streamlined form as ice sheets moved over the debris, they lie with their long axis in line with the direction of the ice's movement. Up to 150 feet high and half a mile long, drumlins often occur in groups on flat plains, where they look like schools of giant leaping porpoises. Among the most famous drumlins is Bunker Hill in Boston, but groups of them can also be seen elsewhere in eastern Massachusetts, in Wisconsin, and in New York State.

Duck

Web-footed waterfowl with waterproof feathers, ducks are birds of oceans, lakes, rivers, and ponds. In contrast to their larger cousins, geese and swans, they generally have shorter legs and necks and broader, flatter bills; and instead of trumpeting or honking, they quack or whistle. Male ducks are more brightly colored than females, but after mating they molt into drab browns similar to the females' plumage. Most species build down-lined nests on the ground near the water's edge, but a few kinds nest in cavities in trees. Unlike geese and swans, ducks do not mate for life; once the eggs have been laid, the males abandon the females and troop off to molt and congregate with other males. Our many kinds of ducks fall into several groups based on appearance and feeding habits. Most familiar are the freshwater dabbling ducks such as mallards, black ducks, teals, and wigeons. Dabblers feed by filtering small plants and animals from the surface or by tipping tailup to pull underwater plants from the bottom. Diving ducks are found on both fresh and salt water. Some, such as canvasbacks and redheads, are mainly vegetarians, while scaups, eiders, scoters, goldeneyes, and buffleheads dive for shellfish and crustaceans. Mergansers are streamlined divers that seize fish with their long, sawtooth-edged bills. Oldsquaws, the deepest divers, can descend to depths of 200 feet. Other ducks include ruddy ducks, which are chunky, broad billed, and stiff tailed, and the whistling ducks of southern marshes, longlegged, long-necked birds with shrill calls.

Duckweed

Of the more than 300,000 known species of flowering plants, the duckweeds are the smallest; one kind is so tiny that a dozen individuals could fit on the head of a pin. Found in still, warm waters, duckweeds are simple, free-floating fronds that have no stems or leaves, and in a few species lack roots as well. Their tiny flowers rarely produce seeds. Duckweeds propagate instead by developing buds that break off and grow into mature plants. Extremely prolific, duckweeds sometimes multiply so rapidly that they completely cover a pond's surface.

Dudleya

Dudleya

Plants of harsh places where little else can survive, dudleyas of various species cling to seaside cliffs in California, hide under the scrub on coastal mountain ranges, and poke up from desert slopes in the Southwest. The plants lie withered and dormant through the summer's heat, but winter rains revive their tidy rosettes of succulent leaves, and in spring they send up stalks of pretty yellow, red, or white flowers. One of the better-known species is the powdery dudleya, a yellow-flowered plant of coastal cliffs that is named for the mealy white coating on its leaves. Another widespread species, canyon dudleya, produces red to yellow flowers; it brightens rocky outcrops in California's Sierra Nevada and the coastal mountain ranges.

Duetting

An Animal Behavior term, this is used to describe the calling of some pairs of Birds, notably Whooping Cranes and Canada Geese, where calls of two members of the pair arc so close together and coordinated that the sequence sounds like the song of a single Bird. Duetting may help to maintain the pair bond as well as having a function in territorial advertisement.

Dumping (Ocean)

The disposal of waste into an ocean.

Dune

Unstable monuments to the combined action of wind and time, dunes are hills of sand found in deserts and along shorelines. Formed in much the same way as snowdrifts, they build up when wind, slowed by an obstacle such as a rock or plant, drops its load of sand on the leeward side. The resultant mound gradually increases in size, in some cases reaching hundreds of feet in height. Some dunes are anchored by vegetation; others migrate many feet each year. In the United States, notable seashore dunes are found on Cape Cod in Massachusetts, and along the Oregon coast. On the shores of Lake Michigan, many dunes are piled 500 feet high and extend for miles. Some of the tallest inland dunes in the country occur at Great Sand Dunes National Monument in Colorado, where they reach heights of more than 700 feet.

Dust devil

On hot, still days when the midday sun blazes down in arid regions, air near the ground heats up and begins to rise. As air rushes in to replace it, the rising air starts to spin. Dust, sand, leaves, and debris also are pulled up into what then becomes visible as a slender, wavering dust devil. Looking like tiny tornadoes, dust devils may rise hundreds of feet. But because they are small and easily disturbed by surface winds, they seldom last more than a few minutes.

Dust storm

Sweeping across the land-often for hundreds of miles-dust storms are strong, dust-laden winds that smother animals and plants, bury crops, and reduce visibility to nighttime darkness. Destructive and awesome, they occur in arid regions with little protective vegetation and in areas where drought has reduced the soil to powdery dust. As winds sweep across the ground, particles are stirred up and held aloft, forming great dark walls that can reach heights of 10,000 feet or more. Although dust storms have always been part of the American scene, the worst occurred on the Great Plains in the 1930's. During those Dust Bowl years, 50 million acres of farmland were destroyed.

Dusty miller

Artemisia stelleriana

A common plant on eastern seashores, dusty miller sports little yellowish flower heads in summer. But its outstanding feature is its felty gray-green foliage, which does indeed have a dusty look, as if it had been sprinkled with flour. The covering protects the leaves from drying out in sun and wind, so that it flourishes even at the ocean's edge. An import from Asia, the plant is cultivated for its attractive foliage. But since escaping from the garden, this perennial has proven an important stabilizer of beaches. As sprawling stems take root across the dunes, they cast a silvery net that slows the shifting sands.

DVD

DVD (sometimes called "Digital Versatile Disc", or "Digital Video Disc") is a modern media format that can be used for recording, storing and playing information, including Computer files, Audio and Video - including movies with high video and sound quality. DVDs resemble a small, shiny round record, and the much more common CDs - as their physical dimensions are the same 4.72 inches or occasionally 3.15 inches in diameter, but they are encoded in a different format and at a much higher density. Different sizes of DVD hold different quantities of information. Two commonly used sizes are DVD5 and DVD9. An "average" DVD holds about 5.7 GB of information.

Eagle

Bold and proud in appearance, eagles have symbolized power since ancient times. Like other hawks, they have keen eyesight, hooked beaks, and long, curved talons for seizing prey. The two North American species, the bald eagle and golden eagle, are similar in size, with eight-foot wingspans, but otherwise differ in several ways. Despite its fierce appearance, the bald eagle, our national bird, is a rather timid hunter. Usually found near water, it feeds mainly on fish, which it often steals from ospreys. Its nest, or aerie, generally built in tall trees, is enlarged year after year and may be as much as 9Y2 feet wide and 20 feet high. In the 1960's bald eagles were reduced in numbers by DDT but have made a comeback since the pesticide was banned.

The golden eagle, which nests on cliffs in western mountains and across Canada, is a bolder hunter than the bald eagle. It captures prey in long swoops and sometimes attacks animals larger than itself. In the past, thousands of golden eagles, thought to be a threat to livestock, were shot from airplanes. Since 1962, however, federal law has protected them.

Earth

This place we live, Planet Earth, is the third planet, and 93,000,000 miles from the sun. It is estimated to be over 4.5 billion years old.

The planet rotates once every 23 hours, 56 minutes, and 4.09 seconds. It makes one full revolution around the sun every 365 days, 6 hours, 9 minutes, and 9.45 seconds. Earth's axis is tilted at a 23.5° angle.

Earth has a total surface area of 196,800,00 square miles. Approximately 57,300,00 square miles, or 29% of the total surface area is land. Water covers approximately 139,500,000 square miles, or 71% of the total surface area.

The highest temperatures on Earth have reached 136° F (58° C) at Al Asisiyah, Libya. Temperatures of - 128° F (-89° C) have been recorded at Vostok station in Antarctica.

The atmosphere is a thin, gaseous layer of air that envelops the planet. Its inner layer is called the troposphere and reaches only 11 miles above sea level. It contains most of the planet's air, which consists of nitrogen (78%) and oxygen (21%). The stratosphere, or outer layer, stretches 11-30 miles above sea level and contains ozone (O3). Ozone filters out most of the sun's harmful ultraviolet radiation.

More than 99% of earth's atmosphere is less than 50 miles (80 km.) high. However, particles of the atmosphere are found 1,000 miles (1,600 km.) in space above the planet's surface.

Earthquake

Among the most dreaded of natural phenomena, severe earthquakes are terrifying events. Their awesome force can topple buildings, buckle bridges, rupture highways, and cause catastrophic loss oflife and property. Fortunately, the most powerful quakes are rare. Of the million or so earthquakes that occur around the world every year, the vast majority are too small to be detected except by sensitive instruments. In the United States, about 700 a year are strong enough to be felt, but most cause no more rumbling than a passing truck.

The earth's crust consists of about 20 gigantic, slowly moving plates. As the plates collide, grind past, or sink below one another, stress builds up along their edges. Finally, the pressure becomes so intense that the crust suddenly gives way, sending shock waves in all directions at thousands of miles per hour. The slippage temporarily relieves the stress, but it also causes the earth to tremble and crack. The largest, most destructive quakes tend to originate near socalled subduction zones, regions where one plate is being pushed beneath the edge of the adjoining plate. When earthquakes occur on the ocean floor, the shock waves can produce swift and devastating tidal waves known as tsunamis. Earthquakes can also be triggered by volcanic eruptions, and some have even been generated by human activities. Pumping liquids into oil fields to force petroleum to the surface, for instance, has resulted in small quakes when the injected fluids lubricated fissures in the bedrock, causing slippage. The magnitude of earthquakes is usually measured on the Richter scale, devised by a California geologist. Each successive whole number on the scale represents a tenfold increase in the force of the earthquake's shock waves. For example, a magnitude of 7 on the Richter scale is 10 times greater than a magnitude of 6, and 100 times greater than a magnitude of 5. The most powerful earthquake to strike North America in recent times, the Alaskan quake of 1964, registered 8.4 on the Richter scale. One of our earliest recorded earthquakes took place in Plymouth, Massachusetts, in 1638. Luckily, none of the Pilgrims were hurt, though houses shook and dishes were shattered. In 1755, another quake that struck New England was felt from Nova Scotia to South Carolina. A far more devasting earthquake centered on the little frontier town of New Madrid, Missouri, at two in the morning on December 16, 1811. As the terrified settlers ran from their cabins, they watched helplessly as the ground heaved and split, spewing gravel and sand into the air. Churning with waves, the Mississippi River overflowed its banks, and bluffs along the river collapsed into the water. In the next few months, two more major earthquakes struck the same area, totally leveling New Madrid. The second was so powerful it caused church bells to toll in Washington, D.C., and stopped clocks in Charleston, South Carolina. This time, the Mississippi reversed its course and then rushed into a newly created depression in the ground, forming gigantic Reelfoot Lake. The earth-shaking shocks continued almost daily for two years. In 1886 a violent earthquake hit Charleston, South Carolina, killing 60 people and destroying much of the city in just 70 excruciating seconds. As in the Missouri quakes, the ground split open, casting silt and water 20 feet into the air, a phenomenon that occurs when powerful shock waves suddenly rip through loose, watery soil. Tremors from the devastating earthquake were felt as far away as Canada.

The Pacific Coast, where two of the earth's giant shifting plates meet, is the continent's leading earthquake zone. More than half of the quakes that strike the lower 48 states occur in California because of its extensive, branching system of faults. The largest of these is the San Andreas fault, where the Pacific Plate slides northwestward against the North American Plate at about two inches per year. Visible on the surface, the fault stretches nearly 700 miles through southern and central California. San Francisco, built astride the San Andreas fault, has a long history of earthquakes. The most violent of these, estimated at 8.25 on the Richter scale, occurred in 1906. It struck at about five in the morning with a roar that survivors compared to a thousand runaway trains. Streets rippled and heaved, water and gas mains ruptured, cornices fell from swaying buildings, wooden houses collapsed, and even massive structures built of stone and brick disintegrated. Dozens of fires sprang up from the broken gas mains and live electric wires, and whole sections of the city went up in flames. The devastating Good Friday earthquake in Anchorage, Alaska, struck on the afternoon of March 27, 1964. At 8.4 on the Richter scale, the quake released energy equivalent to 12,000 Hiroshima-type atomic bombs. Fissures sliced through the city, and entire neighborhoods sank 30 feet below the surface. Nearly 2,000 miles away, a tsunami hit Crescent City, California, drowning 12 people and demolishing the town.

Earthworm

Cylindrical, segmented, legless animals, earthworms move with the help of tiny bristles, called setae, on each body segment. They feed on decaying organic matter in the soil and deposit the residue on the surface as granular castings. Charles Darwin considered earthworms to be among the most important creatures on earth because they encourage plant growth by mixing and aerating the soil as they burrow through it. He estimated that the worms on a single acre of land bring as much as 18 tons of soil to the surface each year. Although they often appear after storms, earthworms do not rain down from the heavens as was once thought: they simply are forced to flee from their water-filled burrows.

Earwig

Inch-long insects with fierce-looking pincers at the rear of their bodies, earwigs trace their name to the superstition that they crawl into the ears of sleeping people. They are, in fact, nocturnal but are harmless to humans. Earwigs do, however, hide in cracks and crevices by day and, because they sometimes cause an unpleasant odor, can be household pests. Those in the West and South sometimes damage cultivated plants.

Echolocation

Bats, porpoises, and a few birds are among the animals that use echolocation to navigate and locate prey. For bats, cave dwellers that live in a world of darkness, this system of sonar provides a means of capturing flying insects even on the inkiest of nights. As they flutter through the air, bats emit short bursts of high-pitched sounds that bounce off objects around them and are reflected back to their large ears. These echoes enable the bats, in effect, to "see" pictures in sound. Porpoises emit clicking sounds whose echoes tell them about the location, size, and shape of prey, and some cave-dwelling birds navigate by means of high-pitched calls.

Echolocation

An Animal Behavior term, this is used to describe orientation by emitting high-pitched sounds and locating the positions of objects by the way in which they reflect the sound. Echolocation is used mainly by bats, but also by Dolphins.

Ecocline

A geographical gradient of vegetation structure associated with one or more environmental variables.

Ecology

Biological Philosophy term. The scientific study of the interrelationship of all life-forms and of their dependency on their environments. By inference: the scientific study of the ties that bind humankind to the natural world. The word is derived from the Greek oikos, a dwelling place. It was coined in German, Oekologie, in 1832 by Ernst Haeckel, a leading German proponent of Darwin. It was "Anglicized at the Madison, Wisconsin, Botanical Congress of 1893”.

Ecology (Ocean)

Ocean ecology deals with the relations of ocean-dwelling organisms to one another and to their physical surroundings.

Ecological community

A set of interacting natural populations.

Ecological effects characterization

The identification and quantification of the adverse effects elicited by a stressor and, to the extent possible, the evaluation of cause-and-effect relations.

Ecological risk assessment

A process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. Ecological risk assessment may evaluate one or many stressors and ecological components.

Ecological risk characterization

A process that uses the results of the exposure and ecological effects analyses to evaluate the likelihood of adverse ecological effects associated with exposure to a stressor.

Economics

The study of how human beings allocate limited resources to produce various commodities and how those goods are distributed for consumption among members of society.

Ecosystem

The totality of components of all kinds that make up a particular environment; the complex of biotic community and its abiotic, physical environment. A local ecological community: coral reef, prairie, alpine, etc. Dynamic and interrelating complex of plant and animal communities and their associated nonliving (e.g. physical and chemical) environment.

Ecosystem Approach

Endangered and Threatened species term.

Protecting or restoring the function, structure, and species composition of an ecosystem, recognizing that all components are interrelated.

Ecotone

A habitat created by the juxtaposition of distinctly different habitats; an edge habitat; a zone of transition between habitat types or adjacent ecological systems having a set of characteristics uniquely defined by space and time scales and by the strength of the interactions(see Boundary).

Ecosystem

A biological community of interacting organisms and their physical environment.

Education (Action and Learning): The process of providing intellectual, moral and social instruction to an individual or group of people, particularly in a formal, prolonged manner. There are many programs and projects aimed at incorporating environmental education into school curricula.

Eden

Biological Philosophy term. The mythic place where Adam and Eve lived before their "fall" into sin, which some interpret as their discovery of self, of consciousness, of self-consciousness, and so, their alienation. It is connected to the Pastoral Ideal.

Edge effect

Changes in a community due to the rapid creation of abrupt edges in large units of previously undisturbed habitat and the tendency for increased variety and density of organisms at community or habitat junctions.

Edge species

Species preferring the habitat created by the abutment of distinctive vegetation types.

Eel

Anguilla rostrata

Long, slender, snakelike fish, American eels have a ribbonlike look as they undulate through the water. They are found in lakes, ponds, rivers, and streams all along the eastern seaboard, but they migrate to the Sargasso Sea in the Atlantic Ocean to spawn. There each female lays as many as 20 million eggs, which the males cover with milt. This prodigious effort is the final act of the adults, for they die before the eggs hatch. The young drift with the currents toward the coast and gradually metamorphose from flat, transparent, leaf-shaped larvae into elvers, miniature, light-colored versions of the adults. The journey to the shore takes about a year; once there, the males remain near the river mouths while the females continue upstream, sometimes slithering across mud flats and wet grass on their way to inland lakes and ponds. When fully grown, from 8 to 20 years later, the eels begin their long swim back to the Sargasso Sea.

Eelgrass

Zostera marina

One of the few flowering plants found in the sea, eelgrass is named for its long, ribbonlike leaves that sway gently with the currents. Growing in dense stands in shallow waters along the Atlantic and Pacific coasts, it was long regarded by fishermen as little more than a propeller-fouling pest. Then in 1931 a mysterious blight virtually wiped out the eelgrass beds. When the thriving bay scallop fishery also collapsed, ecologists realized that the beds are in fact vital nurseries, not only for scallops but for a host of other creatures, too. The subsequent starvation of thousands of brants demonstrated the importance of eelgrass to these geese as well. Fortunately, the eelgrass eventually recovered and once again fulfills its vital role in coastal ecology.

Egret

See Heron.

Eider

Stocky ducks of northern climes, the eiders are best known for their down. Famed for its softness and superb insulating qualities, it has for centuries been harvested from their nests to make eiderdown bedding and parkas. Common eiders, at 27 inches and nearly five pounds, are the largest North American ducks. They winter along the north Atlantic and Pacific coasts and migrate farther north each spring. Feeding on mollusks and crustaceans, these expert divers routinely plunge to depths of 60 feet. The other three species-king, spectacled, and Steller's eiders-all dwell somewhat farther north year-round. Or so it is assumed, for the wintering grounds of the spectacled eider remain largely unknown to this day.

El Niño

El Niño is a warm surface current that usually appears in the Pacific Ocean off Ecuador and Peru around Christmas, and lasts about three months. Every three to seven years it remains for as long as a year-and-a-half as part of a southern oscillation. In North America, this contributes to warmer temperatures along the Pacific coast and weaker hurricanes on the Atlantic.

Elder

Sambucus

Famous for its fruits, which are made into elderberry jam, pie, and wine, the common elder of the East is a shrub up to eight feet tall. In contrast, the treelike blueberry elder of the West often grows 20 feet tall with a trunk 2 feet wide. In summer the elders bear broad clusters of creamy flowers, which are followed by red or purple fruits. A favorite with wildlife, the fruits often are so abundant that the plants' stems break under their weight. All elders, in fact, have brittle wood and pithy twigs that are easily hollowed out to make whistles and drinking straws.

Electrocommunication

An Animal Behavior term, this is used to describe communication by means of electric fields and pulses generated by one individual and detected by others. ElectrocommuniCatlon is used by some Fish in courtship and aggressive encounters.

Elk

See Wapiti.

Elm

Ulmus

Practically every town east of the Rocky Mountains seems to have its Elm Street, for in the post-Civil War building boom, people found the American elm to be an ideal shade tree. Fastgrowing and up to roo feet tall, the graceful vase-shaped trees formed cathedrallike gothic arches over hot roadways; they prospered even in the compacted streetside soil; and they tolerated both drought and periodic flooding. Since the 1930's, however, the trees have been decimated by the deadly Dutch elm disease. Caused by a fungus that is spread from tree to tree by elm bark beetles, the fatal ailment arrived on these shores with a shipment of logs infested with fungus-carrying beetles. One estimate puts the death toll of the last half century at roo million trees. Other shade-producing elms include the hard-wooded rock, or cork, elm and the slippery elm. Like all the elms, they produce small, winged fruits and have elongated, oval leaves with typically lopsided bases. Unfortunately, they too are susceptible to Dutch elm disease.

Elytra

The hard horny forewings of a beetle, which cover and protect the hindwings.

Emancipation

An Animal Behavior term, this is used to describe a suggested process whereby movements shown during Displays have become divorced from their original controlling mechanisms during Ritualization. Thus, grooming and drinking movements acting as signals during courtship may no longer require Motivation to groom or to drink before they appear.

Emergency Response (Action and Learning)

An emergency response is an action carried out in a particular community or region to protect human health and the environment from the impacts of an environmental emergency, such as a forest fire or a chemical spill.

Empiricism

Biological Philosophy term. In its naive form, the belief that one can examine "the facts" without any beliefs or assumptions at all to guide the examination and a hypothesis will emerge. In most cases it appears that scientists begin with a theory, test it empirically, find it wanting, and move toward new theory.

Endangered

Endangered and Threatened species term.

The classification provided to an animal or plant in danger of extinction within the foreseeable future throughout all or a significant portion of its range. Species that are much reduced in number and could disappear in part or all of their range.

Endangered species

Plants and animals whose populations have dwindled to such low levels that they are threatened with extinction are known as endangered species. In some cases species have become so specialized in their requirements that even the slightest change in the environment imperils their existence. In modern times, however, the threats more often result from human interference. In the last century, bison were so ruthlessly slaughtered that they were nearly wiped out before efforts were undertaken to save theI)l from extinction. Even more sinister than hunting and trapping is the destruction of habitat. The elimination of forests and wetlands to build suburbs and shopping malls, and the fouling of whole ecosystems with pollutants and pesticides have taken a devastating toll on wildlife. Before it was banned, for instance, DDT threatened such birds as bald eagles and peregrine falcons by causing them to produce eggs with abnormally thin shells. From the Florida golden aster and the Santa Cruz cypress to the wood stork, the red wolf, and the magnificent blue whale, the list of endangered species is a long one.

Endangered Species Act

1973 Act of U.S. Congress, amended several times subsequently, that elevates the goal of conservation of listed species above virtually all other considerations. The act provides for identifying (listing) endangered and threatened species or distinct segments of species, monitoring candidate species, designating critical habitat, preparing recovery plans, consulting by federal agencies to ensure that their actions do not jeopardize the continued existence of listed species or adversely modify critical habitats, restricting importation and trade in endangered species or products made from them, restricting the taking of endangered fish and wildlife. The act also provides for cooperation between the federal government and the states.

Endangered and Threatened species term.

Federal legislation intended to provide a means whereby the ecosystems upon which endangered and threatened species depend may be conserved, and provide programs for the conservation of those species, thus preventing extinction of native plants and animals.

Endangered species permit

Endangered and Threatened species term.

A document issued by the Service under authority of Section 10 allowing an action otherwise prohibited under Section 9 of the Endangered Species Act.

Endemic

Bird Biology Avian Conservation term.

Confined and native to a certain region. Confined to a geographical area such as an island, state or country.

Endemic species

Endangered and Threatened species term.

A species native and confined to a certain region; having comparatively restricted distribution.

Endpoint

A characteristic of an ecological component that may be affected by exposure to a stressor; a characteristic of valued environmental entities that are believed to be at risk. Distinguished are two types of endpoints:

Assessment endpoint--an explicit expression of the actual environmental value that is to be protected.

Measurement endpoint--a measurable response to a stressor that is related to the valued characteristics chosen as the assessment endpoints.

Energy

Anything that can be efficiently converted into heat or motion to provide power to run machines and vehicles and to supply heat and light is a source of energy.

Energy (Industry)

The energy industry includes businesses that produce power through such means as hydroelectricity and nuclear energy, as well as those that extract and refine energy-producing fossil fuels. Others are involved in the development of alternative energy sources, such as solar and wind power, and fuel cells.

Energy consumption

Energy consumption refers to the amount of energy used by an object, system or process to carry out a particular function.

Enforcement (Law)

Enforcement embodies those activities that compel adherence to legal requirements. These activities include inspection and monitoring; investigation of violations; issuance of notices to individuals or businesses to require them to correct improper practices; issuance of tickets for violations; seizure of wildlife, or their parts and products, and any item that may have been used to commit the offence; and prosecution.

Engram

An Animal Behavior term, this is used to describe the memory trace within the brain, the nature of which is as yet unknown. Many electrical, chemical and anatomical studies of the brain are aimed at discovering its form.

English sparrow

See House sparrow.

Environment

The surroundings on which animals and humans depend for life, especially, but not exclusively, the inanimate environment: air, water, topsoil, weather, wetlands, ozone shield. Physical and biological surroundings of an organism, including the plants and animals with which it interacts.

Environmental assessment

Carrying out an environmental assessment means determining or estimating the value, significance or extent of damage to a particular ecosystem or aspect of it.

Environmental characterization

The prediction or measurement of the spatial and temporal distribution of a stressor and its co-occurrence or contact with the ecological components of concern.

Environmental emergencies

An uncontrolled, unplanned or accidental release of a substance into the environment that may affect human life or health or the environment of which human health depends. These emergencies include those resulting from human activities as well as ones created as a side effect of a natural hazard (forest fires, spills, leaks)

Environmental gradient

A continuum of conditions, such as the gradation from hot to cold environments.

Environmental monitoring

Monitoring, or making systematic geo-referenced observations of the environment-such as measuring water level or counting trees-is essential to detecting changes in ecosystems over time.

Epigamic selection

An Animal Behavior term, this is used to describe sexual selection based on the choice of one sex by the other, usually of males by females, which has led to enormously elaboRated Displays. Such Courtship Displays are often called Epigamic Displays. The classic example is the Peacock's tail.

Epiphyte

Perched on trees, utility wires, and even buildings, the so-called air plants use their roots only to anchor themselves in place; having no contact with the soil, epiphytes get all their nourishment from wind-blown dust and from minerals in rainwater. Epiphytic ferns, orchids, and bromeliads are plentiful in subtropical Florida, while Spanish moss drapes trees throughout the South. In other areas, mosses, liverworts, and lichens are common epiphytes.

Equitability

Evenness relative to any specific standard or model of species abundance and uniformity of abundance in an assemblage of species. Equitability is greatest when all species are equally numerous (syn. evenness).

Ermine

Mustela erminea

Small and agile, with a lithe and sinuous body, the ermine is a ferocious nocturnal hunter that can slip through even the tightest spaces in pursuit of mice and other small mammals. Sometimes known as the short-tailed weasel, it is 12 to 14 inches long, including its 2- to 4-inch black-tipped tail. Twice a year, ermines molt and undergo a complete color change. Chocolate-brown with white underparts in summer, in winter they turn snow-white except for their black tail tips. The beautiful winter pelts are valued as luxury furs and have traditionally been a symbol ofEuropean royalty. Found as far north as the Arctic and south to New Jersey in the East and New Mexico in the West, ermines live alone in forests and brushy areas-anyplace with an abundance of prey and water. Almost perpetually hungry, they help keep rodent populations in check.

Erosion

Bit by bit, the face of the earth is constantly changed by the never-ending process of erosion. Its agents-water, wind, waves, and ice-all have amazing power to move, sculpt, and scar the land. Falling rain, each drop like a little hammer, pounds away at the soil. Streams and rivers strip off sediment and carry it toward the sea. Waves gnaw at sandy shores and pummel seaside cliffs. Mighty glaciers gouge out valleys and, over time, reshape entire mountain ranges. And in the desert, intermittent downpours deepen gullies, while wind-blown sand scours away the surfaces of solid rock. Erosion does not work alone. Weathering first breaks down the rocks by dissolving them with acidic groundwater, by alternate freezing and thawing, and by other means. The smaller pieces can then be moved from place to place. The results of this slow but steady change can be harmful. Millions of tons of topsoil are lost from farmlands every year. But erosion has also created some of our most spectacular sceneryfrom the Grand Canyon, etched into the Colorado Plateau, to the sheer cliffs along parts of the Pacific coast, created by the pounding waves.

Erratic

When the massive ice sheets of the last Ice Age moved slowly across the land, they carried along pieces of bedrock and deposited them far south of their places of origin. Such rocks, called erratics, often differ dramatically from the surface on which they rest in their new surroundings. As a result, they have provided geologists with important clues as to the routes taken by the longvanished ice sheets. These well-traveled relics of the Ice Age range in size from mere pebbles to building-size boulders that weigh tens of tons.

Esker

Steep-sided winding ridges made up of sand and gravel, eskers are remnants of the last Ice Age. The ridges of debris were deposited by streams of water that snaked through passages in and under glaciers, and were exposed when the ice melted. To modem eyes some of the narrower eskers look like railroad embankments. Eskers can be seen in parts of New England as well as in other northern areas that were covered by the great ice sheets. Many of them, however, have long since disappeared, mined for the sand and gravel they contained.

Estimator

A function of sample data that describes or approximates a parameter.

Estivation

The hot-weather equivalent of hibernation, estivation is a state of dormancy that allows animals, particularly those that dwell in the desert, to survive in times of excessive heat and drought. During such periods, the animals become torpid, their breathing and heart rates are reduced, and the need for oxygen and water are greatly diminished. Many insects and snails estivate, as do spadefoot toads and fish that live in ponds subject to drying out. Estivators sometimes wrap themselves in moisture-retaining cocoons; others burrow into the ground while waiting for rain. A few mammals, such as ground squirrels, also become dormant in the hot summer months, but scientists disagree as to whether their metabolic slowdown can be described as true estivation.

Estrus

An Animal Behavior term, this is used to describe the state in female Mammals when they are receptive to a male or "in heat."

Estuary

When, over the course of time, coastal land subsides or the melting of glaciers causes sea levels to rise, the mouths of rivers are drowned, producing bodies of mixed salt and fresh water called estuaries. They may be broad and shallow, like Chesapeake Bay (America's largest estuary), or narrow and deep, like an Alaskan fjord. Many of our great port cities- New York, Baltimore, San Francisco-were built on estuaries, particularly those with protected bays. While an estuary may look placid on the surface, it is in fact a battleground of opposing forces: the river current, laden with soil and other sediments, drives seaward, only to be rebuffed by the relentless tides. A battleground might seem an unlikely setting for a nursery, but the estuary's brackish waters are just that-a rich reproductive habitat for marine life.

Ethogram

An Animal Behavior term, this is used to describe an inventory which lists and describes all the behavior patterns shown by a species.

Ethology

An Animal Behavior term, this is used to describe the biological study of behavior.

Eucalyptus

Eucalyptus

Native to Australia, where they are called gum trees, eucalypti are famous for being the sole food source of koala bears. In the 1850's these attractive evergreens were first introduced to California, where, because of their amazing vigor and tolerance for dry soils, they were widely planted both as ornamentals and in reforestation projects. The blue gum is the tallest and most vigorous species, attaining heights of 50

feet in five years and 180 feet at maturity. On some eucalypti the bark is shed in flakes, giving the trees a mottled appearance, while on others it peels off in shaggy strips. The leathery, lanceshaped leaves contain aromatic oils used in medicines, deodorants, and perfumes, and the wood is used for lumber and fuel.

Eusociality

An Animal Behavior term, this is used to describe the form of society found in some social Insects in which there is coopeRation between individuals and division of labor. For example, some individuals are more or less sterile and others primarily engaged in reproduction. (See Caste.)

Eutrophication

As a lake evolves over time, it becomes enriched with nutrients in a natural aging process called eutrophication. The nutrients, released by the decay of plants and animals, stimulate even more growth and decay, causing silt and organic remains to accumulate on the bottom. Over thousands of years, the lake is transformed into a marsh and finally into dry land. Man-made pollutants, however, speed up the process, causing lakes to age prematurely. The nutrients in sewage and fertilizers foster the rapid growth of algae, which, when they die and decay, use up so much oxygen that fish and other animals literally suffocate. And so, ironically, the lake chokes to death from its own excessive fertility.

Evening primrose

Oenothera

Though the evening primroses favor sunny sites such as roadsides and vacant lots all across America, most of them reserve their blooms for the evening hours. The four-petaled flowers open at sunset and wilt the next morning, a schedule that suits the night-flying moths they depend on for pollination. The blossoms' light colors-yellows, pinks, and whites-show up in the dark, and a sweet lemon fragrance adds to their allure. The most abundant species, the common evening primrose, has six-foot stems that help its inch-wide flowers stand out against the night sky. The Missouri evening primrose, less than one foot tall, compensates for its modest stature with bolder flowers-bright yellow saucers three inches across.

Evenness

The uniformity of abundance between species in a community.

Everglades

Called pa-Hay-Okee-the grassy river-by the Seminole Indians, Florida's Everglades are a 4,000 square mile wetland extending from Lake Okeechobee south to Florida Bay. Most of the Everglades is a vast, nearly flat expanse of sawgrass, a sharp-edged sedge that grows 10 to 15 feet tall. Ponds and channels of open water lace the sawgrass prairie, and here and there the monotony is interrupted by small stands of treesbald cypresses in low places, and virtual jungles of mahoganies, gumbo-limbos, and other tropical species on the hammocks, low islands that rise only a foot or two above the water level. Where the marsh meets the ocean, it is fringed with a broad belt of mangroves, salt-tolerant trees that protect the land from the ravages of wind and waves. And everywhere there is wildlife. Teeming with a staggering variety of species, the Everglades serve as a sanctuary for many rare plants and animals. Ibises, egrets, and other long-legged waders fish in the shallows, while bald eagles roost in the cypress trees. Alligators, deer, marsh rabbits, bobcats, and even the endangered Florida panther all find a haven in this unique waterlogged wilderness.

Evergreen

A tree or plant that retains its leaves throughout the year.

Evergreen forest.

Trees.

Evolution

Biological Philosophy term. A scientific explanation of the development of life from the earliest one-celled animals to the variety of species we see today. The major assertion here is not that there is variation within a species--which is obvious--but that variation can be so fundamental that a new species arises. The mechanism of evolution is Natural Selection. This process does not lead inevitably toward greater complexity or to "higher" forms of life. To say it does is to give Teleology, purpose, to an accidental process. The larger brain of the shark does not indicate, as Louis Agassiz thought, that the shark is a later, higher form of marine animal than fish with smaller brains.

Evolutionarily stable strategy

An Animal Behavior term, see StRategy.

Excess Nutrients (Water)

Excess nutrients such as nitrogen and phosphorus compounds come mainly from municipal sewage and farm runoff containing fertilizers and animal waste. When these nutrients are introduced to lakes, rivers, and marine environments, they can cause excess growth of aquatic plants, which then die and decay, depleting water of dissolved oxygen and killing fish (a process called eutrophication).

Exotic

This term, related to wildlife, usually refers to an alien or introduced species.

Exploitation

The removal of individuals or biomass from a population by predators or parasites.

Exploitation competition

Competition in which two or more organisms consume the same limited resource.

Extinct

The disappearance of plants and animals from the face of the earth is an ongoing process in the life of the planet. Scientists, in fact, estimate that perhaps 90 percent of all the species that have ever lived are now extinct. Mammoths and mastodons, saber-toothed tigers, and countless other creatures have long since died out and are known to us only as fossils. Gone too are all the dinosaurs, victims of a mysterious mass extinction that took place some 65 million years ago. In modem times, however, the pace of extinctions has increased alarmingly. All too often human activity has been to blame, both directly through wanton slaughter and indirectly through destruction or degradation of habitat. Unless vigorous steps are taken to protect and replenish them, more and more endangered plants and animals are doomed to slip into the eternal oblivion of extinction.

Extinct species

Endangered and Threatened species term.

A species no longer in existence.

Extinction

The disappearance of a species, which is always irreversible. The complete disappearance of a species from the earth. The total disappearance of a species from an island (this does not preclude later recolonization).

Extinction

An Animal Behavior term, this is used to describe the process whereby learned behavior ceases to be performed when no longer appropriate. In a Rat, the response of bar pressing to obtain food will slowly decline when the reward is withdrawn; Dogs will cease to salivate to the bell announcing food if it is often rung without food appearing.

Extirpation

The elimination of a species from an island, local area, or region.

Extirpated species

Endangered and Threatened species term.

A species no longer surviving in regions that were once part of their range.

Extractive reserves

Conservation areas that permit certain kinds of resource harvesting on a (theoretically) sustainable basis.

Falcon

Falco

With pointed wings and streamlined bodies, falcons are fast-flying, open-country birds of prey that specialize in catching other birds in flight. Most seize their prey in steep power dives, or stoops, but some also drop to the ground to catch small mammals, insects, and lizards. Unlike hawks, which use their talons to kill their prey, falcons do in their victims with a quick bite on the back of the neck. Falcon nests are simple affairs with little or no lining, usually placed on ledges or in the old nests of other birds. The females lay three to five eggs, which, like the hatchlings, are tended by both parents. The peregrine falcon, clocked at speeds of 175 miles an hour, is the fastest of the falcons. Once found across most of North America, it has declined drastically in numbers because of pesticide residues in the ducks, pigeons, and shorebirds that it feeds on. The prairie falcon lives in dry regions of the West, where it often skims low and flushes birds from the ground. Merlins, small falcons of savannas and open woodlands, prey on songbirds, which they often overtake in swift horizontal attacks rather than downward stoops. The American kestrel, our smallest species, takes more insects and mammals than birds, and hovers as it scans the ground for prey. While most falcons raise only one brood each year, kestrels produce a second in years when mice and voles are abundant.

Fall

Autumn (also known as Fall) is one of the four temperate seasons. It is the transition from Summer into Winter. Autumn is the season during which most crops are harvested and is when most deciduous trees lose their leaves. It is also the season where days rapidly get shorter and cooler, the nights rapidly get longer, and of gradually increasing precipitation in some parts of the world.

Astronomically, some Western countries consider autumn to begin with the September equinox, in the end of September and to end with the December solstice in the Northern hemisphere and the June solstice in the Southern hemisphere. Such conventions are by no means universal, however. Meteorologists count the entire months of March, April and May in the Southern hemisphere, and September, October and November in the Northern hemisphere as autumn.

Although the days begin to shorten after the Summer equinox, it is usually in September (Northern Hemisphere) or March (Southern Hemisphere) when twilight becomes noticeably shorter and the change more abrupt in comparison with the more lingering ones of summer.

Autumn is often defined as the start of the school year, since the children usually begin in early September or early March. Either definition, as with those of the seasons generally, is somewhat flawed because it assumes that the seasons are all of the same length, and begin and end at the same time throughout the temperate zone of each hemisphere. Many ancient civilizations computed the years by autumns, because of Autumn's association with the transition from warm to cold weather, and its related status as the season of the primarychange from one year to the next. The concept of Autumn has dominated the downward cycle in themes and popular images of death and rebirth in many societies. In Western cultures, personifications of Autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Most ancient cultures featured autumnal celebrations of the harvest, often the most important on their calendars. Still extant echoes of these celebrations are found in the late-Autumn holidays of the harvest.

False hellebore

Veratrum

Stately summer-blooming perennials, the false hellebores bear plumes of green, yellow, white, or purplish star-shaped flowers atop stems three to seven feet tall. The delicacy of the blooms provides a pleasing contrast with the plants' broad, boldly pleated leaves, which clasp the stem at their bases. Members of the lily family, the false hellebores are unrelated to the true hellebores, which are old-world relatives of buttercups. And although one western species is known as skunk cabbage, the false hellebores are in no way related to the malodorous wetland plants of that name. All the false hellebores are believed to be poisonous and are occasionally fatal to grazing livestock. Yet the same toxic alkaloids also have the power to heal; they are used in medications for treating hypertension.

Fang

Operating something like hypodermic needles, fangs are the specialized teeth that poisonous snakes use to inject venom into prey. Modified salivary glands produce the poisons, which kill the snakes' victims and assist in digesting them. When a snake is ready to strike, toxins secreted by the glands pass into the hollow fangs, where they are injected into the victim. Some snakes, such as copperheads, have fangs in the front of the mouth that fold back when not in use. On other snakes the fangs remain erect. A third group delivers venom with grooved fangs at the rear of the mouth.

Fannin Sheep

Ovis dalli

A form of mountain sheep. See Dall Sheep.

Fault

Caused by tremendous pressures deep within the earth, faults are fractures in bedrock where the rocks on one side have slipped past those on the other. Faults range in length from a few feet to many miles, and the movement along them may occur a bit at a time or-at high levels of stress-in dramatic, devastating leaps. North America's most famous fault is the San Andreas fault, which slashes across California. It marks the boundary between two of the giant plates that make up the earth's crust, and sudden slips along its length have caused major earthquakes. Other faults are found far from plate boundaries. But no matter where they lie, most are created as the moving plates jostle one other, straining the rigid bedrock until it snaps and thrusts blocks of rock up or down, right or left, along the fracture. So-called fault-block mountains, such as the Sierra Nevada in California, formed when a crustal block was heaved up and tilted along a fault.

Fecundity

Rate at which an individual produces offspring, usually expressed only for females.

Federal action agency

Endangered and Threatened species term.

Any department or agency of the United States proposing to authorize, fund, or carry out an action under existing authorities.

Feedback

An Animal Behavior term, this is used to describe the modifiCation of behavior in response to its consequences. In negative feedback, the consequences slOwly suppress the behavior, as when grooming removes the irritation that caused it. Positive feedback has the opposite effect leading to more of the behavior, for example where sexual stimulation leads to more sexual behavior and so on until terminated by ejaculation.

Feldspar

The most common group of minerals in the earth's crust, feldspars are the main components of many types of rocks and occur in a range of colors. One kind provides the fleshy pink tone that characterizes some of the granites. Another variety, labradorite, displays a rainbow of colors and can be polished into gemstones, as can milky white moonstone and the green variety called Amazon stone. When decomposed by weathering, feldspars form clay, which can be used in the manufacture of glass and ceramics.

Feral

Escaped from domestication. Feral individuals may be descendants of the original escapees. Feral means that a species has returned to the wild.

Fern

An ancient class of plants that dominated the earth hundreds of millions of years ago, ferns are indeed rather primitive looking. Most have delicate, feathery leaves, or fronds; grow close to the ground; and prefer damp, shady areas. When the young leaves, aptly called fiddleheads, first appear, their tips are tightly coiled, and they gradually unfurl into mature fronds. The small dark spots on the undersides of the fronds are clusters of spore sacs that eventually burst open and scatter dustlike spores to the wind. When the spores land, they develop into tiny intermediate plants that reproduce sexually, and it is their offspring that grow into the familiar spore-producing fern plants. Of our 300 species of ferns, two of the more common and typical examples are the elegant ostrich fern and the ubiquitous bracken. Some of the others are nonconformists. The walking fern, for example, sprouts new plantlets at the tips of its long, narrow leaves and reroots itself as it "walks" across the soil. The shoestring fern, an epiphyte that never touches the ground, has yard-long strap-shaped fronds, which dangle like ribbons from rough-barked trees in Florida and Georgia. Other mavericks include ferns that float and a few climbing vines.

Ferret

Mustela nigripes

A secretive but inquisitive member of the weasel family, the endangered black-footed ferret is one of our rarest mammals. This slim-bodied, shortlegged native of the Great Plains is an appealing creature with a black mask across its eyes and with dark feet and a dark tail tip accenting its yellowish coat. The ferret feeds on ground squirrels, mice, and ground-nesting birds, but its favorite prey is the prairie dog, whose underground burrows it takes over as its home. Active at dusk and by night, the ferret makes chattering sounds and hisses when alarmed. With the decline of prairie dogs-considered pests by farmers, who have waged constant war against them-the black-footed ferret's very existence has been threatened. By the 1980's, the last known wild colony was on the brink of extinction. Its plight prompted an intensive captive breeding program aimed at saving the ferrets and returning them to their native plains.

Fiddler crab

Uca

Low tide on sandy or muddy seashores and in salt marshes brings out fiddler crabs in droves. Emerging from their burrows, where they find protection from fish and other predators, the little crustaceans scuttle sideways across the surface, feeding on algae and other plant material. Then, when the tide comes in, the fiddlers head back for the safety of their burrows and carefully plug the entrances. Male fiddlers are easily recognized by their one greatly enlarged pincer, or claw, which they wave about in self-defense and as part of their courtship rituals. The crabs are named for the males' habit of moving the oversized claw back and forth with a sawing motion that looks much like a fiddler fiddling.

Filefish

With bodies flattened from side to side and a single spine projecting, unicorn-style, from the top of their heads, filefish are strange-looking creatures that were named for the sandpaperlike texture of their scales. Usually found near wharves and reefs along the Atlantic coast, filefish swim along slowly, stopping now and then to munch on sea fans, algae, sponges, and even stinging corals. They often hover head down as they forage, and can change color to blend with their surroundings.

Film

Film is a term that encompasses motion pictures as individual projects, as well as the field in general. Many other terms exist for an individual motion picture, including picture, picture show, photoplay, flick, and most commonly, movie. Additional terms for the field in general include the big screen, the silver screen, the cinema, and the movies.

Films are produced by photographing images in a rapid sequence on a long roll of perforated plastic-like material. This resultant product comprises a series of individual frames, and each is literally only a single still photograph, but when these images are shown rapidly in succession, the illusion of motion is given to the viewer. Flickering between the single frames not seen due to an effect known as "persistence of vision", whereby the eye retains a visual image for a fraction of a second after the source has been removed. Also of relevance is what causes the perception of motion; a psychological effect. Film is considered by many to be an important storage medium for historic and scientific events; Quite amazingly, films entertain, educate, enlighten and inspire audiences. The visual elements of cinema need no translation, giving the motion picture a universal power of communication. Any film can become a worldwide attraction, especially with the addition of additional soundtrack editing changes that translate the dialogue. Films are also artifacts created by specific cultures, which reflect those cultures, and, in turn, affect them.

Filter feeding

An Animal Behavior term, this is used to describe a method of feeding used by some Animals whereby they filter small particles from the surrounding medium as they move through it, as in Whaless, or as it moves past them, as in barnacles.

Finch

In addition to finches and goldfinches, the finch family includes the pine siskin, the redpolls, the cross bills, and the evening and pine grosbeaks. Seedeaters all, most of the finches have stout, conical bills that are ideal for crushing such fare. Many finches even feed seeds to their nestlings. (Most other seed-eating birds raise their young on a diet of insects.) And one, the American goldfinch, delays nesting until late summer when seeds are most plentiful. Most of the finches are birds of open woodlands or fields. Rosy finches, however, nest on alpine and arctic tundra, and house finches, once exclusively southwestern birds, now thrive in eastern cities. The eastern birds are descendants of caged finches that were released in 1940. In winters when northern seed crops fail, finches sometimes fly south in exceptionally large numbers. Pine siskins, for instance, may roam from Canada and the northernmost states all the way to the Gulf Coast in search of food.

Fine-grained

Referring to qualities of the environment that occur in small patches with respect to the activity patterns of an organism. This results in the organism's inability to distinguish qualities usefully.

Finger lake

During the last Ice Age, tongues of glacial ice sometimes advanced along north-south river valleys, gouging them out and greatly deepening them. When the ice later retreated, it sometimes left small moraines that dammed the ice-gouged hollows and created long, narrow lakes. Such lakes are called finger lakes after the most famous examples of their kind, the Finger Lakes of western New York.

Fir

Abies

Though a few other evergreens are called firs, our nine species of true firs are unmistakable. Their cones, unlike those of other conifers, stand upright on the branches; the axis of each cone, moreover, remains attached to the tree after its seeds and scales are shed, leaving an erect pencillike spike. The firs also are known for the blisters of aromatic resin that collect under their bark. It is this sticky substance that gives the popular Christmas tree, the balsam fir, its pleasant holiday fragrance. While the balsam fir ranges across much of the Northeast and Canada, and the equally widespread white fir grows from California to the Rockies and south into Mexico, some of the other firs have more limited ranges. The Fraser fir, for example, survives only on the highest peaks of the Appalachians, and the bristlecone fir is confined to canyons in California's Santa Lucia Mountains.

Firefly

Also called lightning bugs, fireflies are actually small, slow-flying beetles that brighten the sky with their blinking lights on summer evenings. Each species has its own characteristic pattern of flashes, which the insects use for finding mates. The males fly about flashing a signal from a light organ on the abdomen, and females hiding on vegetation respond with flashes that announce their readiness to mate. Some females can also mimic the signals of other species: males fooled by this apparent invitation fly down, only to be eaten by the deceptive temptress. After mating, the females lay eggs on moist ground. The larvae, sometimes seen glowing on damp lawns, prey on snails and small insects.

Fireweed

Epilobium angustifolium

Often the first plant to grow in fire-scorched areas, fireweed adds a striking note of color as it springs to life from charred soils. Useful as well as beautiful, it produces seeds by the thousands, each one equipped with a tuft of silken hairs that allows the seeds to drift for long distances on the wind. After settling to the ground, the seeds lay dormant, sometimes for years, until fire strips away the shade and sunlight warms the soil, enabling them to germinate at last. Taking nutrients from the ashes, fireweed spreads a mat of roots through the soil, protecting it from erosion until shrubs and trees reestablish themselves. Found from Labrador to Alaska and south to California, Arizona, South Dakota, and North Carolina, fireweed stages a spectacular show when it comes into bloom. From July to September, spires of showy four-petaled magenta-pink blossoms top its six-foot stalks, which are lined with willowlike leaves. The flowers are followed by slender pods, which soon burst open to launch their downy seeds.

First-year bird:

Bird Biology Avian Conservation term.

A bird in its first 12-16 months (or until its second prebasic molt).

Fish

A cold-blooded, limbless, vertebrate that lives wholly in water and has fins, internal gills, and skin with a glandular secretion that decreases friction. By far the most numerous of all our animals with backbones, fish are cold-blooded, waterdwelling creatures that breathe through gills. Beyond that basic definition, however, it is difficult to generalize. Almost anyone would recognize a carp or a tuna as a fish: like most of their kind, they have paired gills, fins for swimming, and scale-covered bodies that are tapered at both ends. But fish come in an enormous array of shapes and sizes, ranging from less than half an inch to more than 40 feet and weighing from less than an ounce to thousands of pounds. Fish also display vastly different characteristics. They are as varied as the pancake-flat flounder, with its oddly placed eyes; the batfish, which uses its fins for walking across the ocean loor; and the bizarrely shaped seahorse. There are fish armed with swords, others with fishing lures, fish that produce electricity, and even fish that can crawl about on land. And fish live in nearly every imaginable watery habitat, from mountain lakes to murky ocean depths and from steaming hot springs to frigid polar seas.

The vast majority of the 2,000 or so North American species are bony fish, meaning their skeletons are made primarily of bone. These most advanced of all fish are usually equipped with gas-filled swim bladders, used for controlling buoyancy. Other fish, such as sharks, rays, and skates, have skeletons of cartilage rather than bone. Lacking swim bladders, they must remain constantly on the move to keep from sinking. The most primitive fish-the eellike lampreys and hagfish-lack jaws and instead have sucking mouths lined with teeth. The bony and the jawless fish usually reproduce by spawning, with the males fertilizing the eggs after the females have released them into the water. On the other hand, sharks and rays mate, and in most cases the females bear live young.

Fish Stocks (Ocean)

The supply or quantity of fish acquired or allowed to accumulate for future use.

Fisher

Martes pennanti

A brownish-black, bushy-tailed member of the weasel family, about the size of a small fox, the fisher is a stong, aggressive, agile hunter active by night. It lives in dense forests across northern North America, where it roams widely over a home territory of up to 10 square miles. Although the fisher occasionally eats fish, its diet consists primarily of rodents, porcupines, and snowshoe hares. Running, swimming, and climbing trees in pursuit of prey, it can track with the persistence of a wolverine, fend off dogs, and kill animals as large as deer and lynx. Solitary for most of the year, fishers pair off with mates from January through April. Well before giving birth to one to four blind, helpless young, the females make dens in hollow trees, logs, or under rocky ledges. Overtrapped in the past for its handsome pelt, the fisher is now protected and is valued for its role in controlling porcupine numbers.

Fishing (Recreation)

The catching of fish, either as a job or a hobby.

Fitness

An Animal Behavior term, this is used to describe the measure of an individual's genetic contribution to the next geneRation. The term Inclusive Fitness is used to refer not only to the fitness an individual achieves through its own reproductive efforts, but also the Improved Fitness it achieves through assisting relatives to reproduce. Animals are thought to behave in such a way as to maximize their inclusive fitness.

Fitness

Bird Biology Avian Conservation term.

The average contribution of one allele (i.e., one form of a gene) or genotype to the next generation or to succeeding generations, compared with that of other alleles or genotypes. It may be either an absolute value, measured by the number of progeny per parent, or it may be relative to some reference genotype.

Fixed action pattern

An Animal Behavior term, this is used to describe any stereotyped movement pattern found in more or less identical form throughout a species, at least among Animals of similar age and sex. Their relative fixity makes such movements especially useful in classifying Animals and in analyzing behavior. As they are not as fixed as originally thought, the term Modal action pattern has Been proposed as preferable.

Fjord

As Ice Age glaciers moved slowly down existing river valleys on their journey to the sea, they carved deep into the bedrock and excavated the spectacular inlets that we know today as fjords. Although fjords are relatively shallow at their entrances, farther inland they may reach depths of 4,000 feet. Distinguished by dramatically soaring walls, these unique waterways often have waterfalls cascading down their sides, which further enhance their beauty. Although fjords are most often associated with Norway (the word itself is Norwegian), many spectacular examples can be seen in Alaska, especially at Kenai Fjords National Park on the state's rugged southern coast. A setting of breathtaking beauty, the park is home to seals, sea otters, sea lions, and a host of seabirds. But Somes Sound, on the picturesque coast of Mount Desert Island in Maine, is the only fjord in the lower 48 states.
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Flamingo

Phoenicopterus ruber

A bird that has come to symbolize not only Florida but all things tropical, the greater flamingo is unmistakable with its exotic pink plumage, stiltlike legs, and graceful, swanlike neck. Standing three to five feet tall, it feeds by dipping its curved bill upside down in brackish water, then using its thick, fleshy tongue to force mud and water through sievelike structures on the bill that strain out algae, tiny shellfish, and other small animals. Gregarious birds, flamingos live in large colonies on isolated lagoons, where they build moundlike nests of mud and where each pair raises a single chick. The few truly wild flamingos that tum up in Florida come from colonies in the Bahamas. The ones most often seen there are not wild at all, but the semidomesticated denizens of parks and gardens.

Flatfish

In contrast to other fish, the bottom-dwelling flatfish-flounder, sole, halibut, and the likeswim on their sides. They begin life swimming upright like "normal" fish, but then something peculiar happens: one eye begins to migrate across the head toward the other eye, and in some species the mouth becomes twisted as well. The body also develops the typical flattened, oval form of adult flatfish and becomes colored on the eyed upper side and pale on the eyeless underside. Once the transformation is complete, flatfish sink to the bottom of the sea, where they often lie partially buried in mud or sand. Frequently covered with spots and blotches, they are perfectly camouflaged. Some flatfish can even change their color to match almost any background. Active predators, they dart quickly upward to snatch unwary crustaceans, squid, and smaller fish. While flatfish average a foot or two in length, some kinds are much larger. The Atlantic halibut can be more than eight feet long and weigh some 700 pounds, and the Pacific halibut is nearly as big. The most beautiful flatfish, the peacock flounder of warm Florida waters, is named for the brilliant blue markings on its body. Another, known as the windowpane, is a remarkably thin-bodied flatfish that ranges from Canada to South Carolina. Unlike its relatives, most of which are featured on seafood menus, the windowpane is simply too flat and meatless to be valued as a food fish.

Flatworm

Simple, soft-bodied invertebrates, flatworms fall into three main classes: the mostly free-living turbellarians and the parasitic tapeworms and flukes. The best-known turbellarians are the freshwater planarians. Less than an inch long, these worms have been much studied because of their remarkable regenerative abilities; if cut in two, the rear end of a planarian grows a new head, while the head end grows a new rear. The parasitic tapeworms, which absorb food through their body walls, live inside other animals. Beef tapeworms, which mature in the human intestine, can be as much as 30 feet long. They may weaken their hosts by competing for food but usually cause no damage. Many of the parasitic flukes, in contrast, cause serious diseases. The sheep liver fluke, for instance, inhabits the bile ducts of sheep and cattle and is responsible for the disease known as liver rot.

Flax

Unum

Once grown on every farm, flax was so valued in colonial America that authorities required every household to produce a certain quota of flax yam and offered prizes to those who wove the homegrown fiber into linen cloth. Now, however, flax cultivation is limited to California and the Pacific Northwest, where it is no longer grown for fiber, but for the flaxseeds that yield the linseed oil used in linoleum, oilcloth, paints, and varnishes. Imported from Europe, where it had been used for making rope, fishnets, and fabric since ancient times, flax has escaped from cultivation and now survives in fields and waste places as a graceful annual wildflower up to three feet tall. Clusters of small five-petaled sky-blue flowers open as early as February in some parts of the country, and blossoming continues until September, adding cheerful splashes of color to the sandy, well-drained sites the plant favors. Several native flaxes also grow throughout the country, including a yellow-flowered species found in Eastern woodlands and a copper-colored variety that thrives from Texas to Canada.

Flea

Tiny blood-sucking insects that live on dogs, cats, rodents, birds, and humans, these wingless pests can move easily through hair and feathers. Equipped with powerful leg muscles, fleas also can leap indiscriminately from one host to another. The dog flea, one-tenth of an inch long, can jump seven inches high and more than one foot horizontally. Dog fleas, translucent, wingless, and almost microscopic, are nonetheless a bane to animals and humans alike. As they move from animal to animal, fleas help spread a number of ailments. The dog flea, for example, is involved in the transmission of the dog tapeworm. Another, the oriental rat flea, is notorious for its role in spreading the dreaded bubonic plague.

Fleabane

Erigeron

Whether low and sprawling or growing up to three feet tall, the fleabanes all bear daisylike flowers in shades of white, pink, purple, blue, or more rarely, yellow or orange. Found from coast to coast in habitats that range from moist meadows to dry rocky slopes, the plants might easily be confused with asters, except that most of the fleabanes bloom earlier, in summer rather than the fall. Their name recalls a time when pungent fleabanes were hung in homes to drive away fleas. Today some of them serve a similar purpose, with oil of fleabane being used as an ingredient in insect repellants.

Fledge

This is the term used to describe a nestlings first flight, usually when it leaves the nest.

Fledging success

Bird Biology Avian Conservation term.

The average number of offspring fledged (i.e, raised until they leave the nest) per female; percentage of hatchlings that fledge.

Flicker

See Woodpecker.

Flint

See Chert.

Flood

Among nature's most destructive phenomena, floods occur when heavy rains or rapidly melting snow cause streams or rivers to overflow their banks and spill water on land that is normally dry. A river flood of this sort may mean little more than a mild soaking of the surrounding land, or it may result in a major disaster in which people, homes, bridges, and everything else are swept away. In mountainous areas, torrential downpours sometimes result in the massive and rapid runoff of flash floods, which often strike without warning. In 1972 a flash flood in Rapid City, South Dakota, killed more than 200 unwary people.

Floods also occur in coastal areas, when hurricanes batter the shore and swamp low-lying areas with storm-driven walls of water. Even more frightening are tsunamis, tidal waves generated by earthquakes on the ocean floor; they pummel everything in their path as they submerge the coast beneath mountainous waves.

One of our worst floods, in 1889, was caused not by nature but by human neglect. A dam burst near Johnstown, Pennsylvania, and sent a raging torrent into the valley below, sweeping away homes, locomotives, and everything else in its way. More than 2,000 people lost their lives in the disaster.

Flooding (Water)

An overflowing of water beyond its normal confines, and especially over land. Flooding may occur as a result of heavy rainfall and, in spring, as the result of a sudden melting of ice and snow.

Flood plain

The flatlands bordering a river and composed of sediments deposited by the river are called its flood plain. When a river is moving swiftly, particles of sand and silt are carried along in suspension, but when the river overflows its banks in flood, the water immediately slows down and drops its load of sediment, forming the plain. The flood plains of young streams may be only a few feet wide, while those of older, meandering rivers like the Mississippi can stretch for miles.

Floret

A small flower.

Floristic

Referring to studies of the species composition of plant associations.

Flounder

See Flatfish.

Flower

Whether large and showy or small and inconspicuous, all flowers serve the same purpose: they produce the seeds that enable flowering plants to perpetuate their kind. While their structure varies from species to species, the basic design includes one or more female organs, called pistils, at the center; these are surrounded by male organs, called stamens, and then by rings of petals and sepals. The sepals, usually green, enclose the bud before the flower opens. The petals, often colorful, serve to attract pollinators such as bees and butterflies. Each stamen consists of a pollen-bearing structure (the anther) atop a slender stalk (the filament). The pistil has a sticky or fuzzy top, called the stigma, which traps pollen. Once a grain of pollen has landed on the stigma, a tube grows down the necklike style into the ovary, where the plant's egg cells, or ovules, are fertilized and develop into seeds. There are countless variations on this basic plan. Besides differences in the number, size, shape, and arrangement of the various parts, for example, some species have separate male and female flowers or even male and female plants.

Flowering plant

From grasses and wildflowers to towering trees, flowering plants far outnumber such nonflowering types as conifers, ferns, and mosses and truly dominate the earth today. Despite differences in size, shape, and habitat, all flowering plants are similar in the way they reproduce. In contrast to the seeds of conifers, which are borne unprotected on the scales of cones, the seeds of flowering plants are enclosed within ovaries that, sometimes along with other floral parts, develop into fruits.

Fly

Distinguished by having just one pair of wings (most insects have two pairs), the true flies nevertheless are able fliers. The adults of some species drink nectar and other liquids, some kinds suck blood, and others eat nothing at all. The larvae of many flies are known as maggots and feed on dead and decaying organic matter.

Perhaps the best-known member of the group is the house fly, a pest that breeds in filth and transmits such diseases as typhoid fever and cholera. Mosquitoes also are true flies. The females are the ones that bite, with various kinds transmitting malaria, yellow fever, and other illnesses. The black fly, another pest, has a vicious bite that is all too familiar in wooded areas of the Northeast in early summer. Flies can, however, be useful as well. Some kinds parasitize insect pests and help keep them under control. Many are eaten by larger animals. Because of their impressive reproductive potential, flies have found their way into the research laboratory: geneticists are quick to point out that significant advances have been made in the field of heredity by studying the characteristics of succeeding generations of fruit flies.

Flycatcher

Nearly three dozen species of flycatchers, including the kingbirds, the phoebes, and the wood pewees, are found in North America. They earned their name from their habit of darting from perches to snatch passing insects in flight. Alert and upright in posture, the birds flit swiftly out to snap up prey, often with an audible click of their broad, flattened bills. Ranging up to 16 inches in length, most flycatchers are rather drab and nondescript, clad in olive, brown, or dull gray. One exception is the male vermilion flycatcher, which is bright red and black. Another, the scissor-tailed flycatcher, is pale gray with pinkish sides and very long outer tail feathers. Besides being beautiful, the scissortail is notable for its courtship ritual. The male flutters downward in an intricate flight pattern, concluding his descent with several neatly executed somersaults. The scissortail and most other flycatchers build cup-shaped nests, generally in the open but sometimes in tree cavities or crevices in rocks. All species are territorial, with the kingbirds even attacking crows and hawks that trespass on their turf.

Flying fish

Often taking to the air in swarms, silvery, bulletshaped flying fish can sail above the sea at 35 miles per hour. By spreading their enlarged pectoral (forward) fins like wings and sculling with their tails, they become airborne and glide above the waves, sometimes for hundreds of feet. They fly not to amuse themselves but to escape predators such as tuna and dolphinfish. Each species is dubbed either monoplane or biplane, depending on whether its members use just the pectoral fins alone or both the pectoral and pelvic (rear) fins to glide. Among the more common biplanes are the Atlantic and the California flying fish. The latter, at 18 inches, is one of the largest members of the family and is considered excellent eating.

Flying squirrel

Big-eyed and covered with soft velvety fur, these charming creatures of the treetops do not actually fly, as their name implies, but glide from tree to tree. Launching themselves from limbs, flying squirrels spread out the folds of skin that extend along each side between front and hind legs, and sail through the air. Using their broad tails as rudders, they can glide for 150 feet. Strictly nocturnal, flying squirrels love old, rotten trees with plenty of cavities and snags. Some build nests ofleaves and lichens, but most prefer to use old woodpecker holes as dens and nurseries. Sociable creatures, they frequently share their dens with other squirrels. About 10 inches long, including the tail, the southern flying squirrel inhabits broad-leaved and mixed forests throughout the eastern half of the country. Its larger relative, the northern flying squirrel, is found in evergreen forests in the northern states and Canada, as well as farther south in the mountains.

Flyway

Bird Biology Avian Conservation term.

A broad-front band or pathway used in migration.

Flyway

On their seasonal flights to and from their breeding grounds, many migratory birds travel along well-defined north-south routes known as flyways. Broad in some places and narrow in others, these paths provide links between feeding areas, where the birds can stop to rest and refuel. The four main flyways in North America are the Atlantic Flyway, along the Atlantic Coast; the Mississippi Flyway, which follows the Mississippi Valley; the Central Flyway, more or less parallel to the Rocky Mountains; and the Pacific Flyway, along the Pacific Coast. Ducks, geese, and swans are the birds that most commonly use these migratory corridors. For these waterfowl, the flyways connect important marshes, lakes, and wildlife refuges. Other birds, such as shorebirds, also rely on feeding areas along the routes-stopovers that are essential for their survival. The loss of even one feeding site (to development, for instance, or to pollution) could interfere with migration, because the next stop on the route might be too far away for the hungry, tired birds to reach.

Fog

The dense, ground-hugging clouds of suspended water droplets known as fog can cover the land like clammy shrouds. They often occur on calm, clear nights when the ground cools, chilling the air above it enough for water vapor in the air to condense into visible droplets. Fog may also result when cold air passes over warm water, causing a steamy cloud to form. Conversely, it can form when warm, moist winds blow over chilly land-along a seacoast, for example-or a cool ocean current. In many areas, dense fogs pose a hazard to motorists and sometimes cause delays at airports.

Fold

Caused by movements in the earth's crust, folds are bends in rock layers. Although rocks are rigid, if enough pressure is applied they become plastic and can be bent or warped without breaking. The resultant rumples vary greatly in size. Some folds are mountainous in scale and extend for miles. Others are gentle ripples only a few inches long. Folds that sag downward are called synclines; those that arch up are known as anticlines.

Food chain

Bird Biology Avian Conservation term.

A feeding sequence, such as seed-to-songbird-to-raptor, used to describe the flow of energy and materials in an ecosystem.

Food web

An abstract representation of the various paths of energy and material flow through populations in the community.

Fool's gold

See Pyrite.

Foraminiferan

Single-celled, mostly marine animals found in all oceans, foraminiferans are best known for their beautiful, elaborately structured shells, which in most species are composed of calcium carbonate. Threadlike extensions of the body protrude through tiny holes in the shells, enabling the animals to move and feed. When the creatures die, their shells sink to the bottom. So numerous are they that their remains form an ooze covering about 30 percent of the ocean floor. And so abundant have they been over the past 420 million years that in many areas foraminiferan fossils are the major component of massive deposits of limestone and chalk.

Forecasts (Weather)

Predictions of the weather for the next few hours or days made by using computer models to analyze atmospheric data. Long-range weather forecasts, which are more general and less accurate, are also made for future periods of several months.

Forest

A forest is an area with a high density of woody growth, as a wilderness area or, historically, a wooded area set aside for any number of reasons. Many forests have been cut and eliminated by mankind. There are many definitions of a forest, based on various criteria. These plant communities cover large areas of the globe and function as animal habitats, constituting one of the most important aspects of wildlife preservation.

Although often thought of as carbon sinks, mature forests are approximately carbon neutral with only disturbed and young forests acting as carbon sinks. Nonetheless mature forests do play an important role in the global carbon cycle as stable carbon pools, and clearance of forests leads to an increase of atmospheric carbon dioxide levels.

Forests can be found in all regions capable of sustaining tree growth, at altitudes up to the very tops of mountains and they thrive except where natural fire frequency is too high, or where the environment has been impaired by natural processes or by human activities. As a general rule, forests dominated by (broadleaf forests) are more species-rich than those dominated by evergreens (conifer, montane, or needleleaf forests), although exceptions exist (for example, species-poor aspen and birch stands in northern latitudes). Forests sometimes contain many tree species within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests). Forests are often home to many animal and plant species.

These existence of these wildlife populations per unit area is high compared to other vegetation communities. Much of this biomass occurs below-ground in the root systems and as partially decomposed plant humus. In a forest the branches and foliage of separate trees often meet or interlock, although there can be gaps of varying sizes within an area referred to as forest. A woodland has a more continuously open canopy, with trees spaced further apart, which allows more sunlight to penetrate to the ground between them.

Forest fragmentation

Patchwork conversion and development of forest sites (usually the most accessible or most productive ones) that leave the remaining forest in stands of varying sizes and degrees of isolation.

Forest-interior species

Species that tend to avoid edge habitats and that require large tracts of forest habitat for nesting and foraging.

Forestry (Industry)

The management of forests for wood, water, wildlife, forage, and recreation. Due to wood's economic importance, forestry has been chiefly concerned with timber management, especially reforestation, maintenance of existing forests, and fire control.

Forget-me-not

Myosotis

Flourishing along stream banks and in other moist locations across the country are several kinds offorget-me-nots, among them the familiar five-petaled sky-blue flower with the bright yellow eye at its center. Erect or sprawling plants no more than two feet tall, these delightful wildlings bear their dainty nosegays of blue, white, or occasionally pink blooms from late spring until early fall.

Formal consultation

The consultation process conducted when a Federal agency determines its action may affect a listed species or its critical habitat, and is used to determine whether the proposed action may jeopardize the continued existence of listed species or adversely modify critical habitat. This determination is stated in the Service's biological opinion.

Fossil

Each one a bit of evidence in the mystery of life's past, fossils are remnants of plants and animals that have been preserved from prehistoric times. Most were formed when dead plants or animals were quickly buried, protecting them from scavengers. Since flesh and other soft parts usually decayed before they could be preserved, the most common fossils are teeth, bones, shells, and other hard parts. The majority of fossils are petrified, or turned to stone. In some cases dissolved minerals simply filled the tiny air spaces in bones or shells, strengthening the original object. In other cases all of the original animal or plant gradually dissolved and was replaced bit by bit by minerals. Natural molds were formed when entire organisms disappeared after sediments hardened around them. If minerals later filled the mold, the result was a natural cast-an exact replica of the organism. Flat objects such as leaves or feathers often left thin molds called prints. Fossils of insects are often found in amber, or fossilized resin, where they were trapped in ancient times. The footprints of dinosaurs and other extinct animals were sometimes preserved in hardened mud and clay. In rare instances, the entire bodies of mastodons and other large animals were preserved in ice or tar. Fossils are found only in sedimentary rocks, such as limestone, sandstone, and shale. While erosion sometimes exposes them on the surface of the earth, most collectors know that manmade quarries and road cuts are among the best places to hunt for these clues to life long ago.

Four-o'clock

Mirabilis

Named for their habit of blooming as the day wanes, the four-o'clocks are handsome, brightly colored wildflowers. The Southwest claims the greatest variety, including the sweet fouro'clock, which flaunts six-inch tubular blossoms of white or pink atop sticky three-foot stems. Another one-the Colorado, or desert, fouro'clock- is a sprawling annual that yields spectacular displays of two-inch purplish trumpets.

Fox

Traditional symbols of cunning and craftiness, foxes are, in fact, agile, intelligent, and above all, adaptable creatures. Bushy-tailed, long-snouted members of the dog family, they are quick and skillful hunters that eat a broad range of wild fare, including insects, rabbits, berries, and all sorts of rodents. The most common and widespread of the North American foxes are red foxes. Surprisingly small under their luxurious, usually flame-red coats-on the average, about 10 pounds-they hunt in fields and along woodland edges with catlike stealth. Gray foxes, also widespread but most common in the South, are unusual in their ability to climb trees-a rarity in the dog family. The Great Plains and arid Southwest are home to the tiny kit foxes, nocturnal hunters distinguished by their oversized ears. The Arctic foxes, in tum, live in the Far North. Brown or gray during the summer months, they spend their time hunting on the tundra; in winter they tum white and move out onto the pack ice, scavenging in the wake of polar bears.

Foxglove

Digitalis

Pretty but poisonous, the foxgloves are powerful medicinal plants. An extract of their leaves, digitalis, is one of the most effective medicines for certain heart diseases. During their first year of growth, these robust biennials form lush rosettes of ground-hugging, wrinkled, tongue-shaped leaves. Then, in their second season, they send up tall stalks lined with lovely bell-shaped flowers. The common foxglove, native to Europe, was introduced by physicians in the 1700's; its spires of purpleflecked rose or white blossoms now brighten shady spots across most of North America, particularly in the Pacific states.

Fractal dimension

An index of the complexity of spatial patterns.

Fractal geometry

A method to study shapes that are self-similar over many scales.

Frequency

Bird Biology Avian Conservation term.

The number of plots, stations, counts (visits), or intervals in which a species is detected; when expressed as a fraction of the total sampled, it becomes relative frequency.

Freshwater

Water that is not salty, found in inland bodies of water.

Fritillary

Boldly patterned with dark spots on the upper sides of their wings and, in many cases, with silvery spots on the undersides, the tawny to orange fritillaries include some of North America's most striking butterflies. The larger kinds, known as the greater fritillaries, are so named for their broader wingspans; they flit over meadows and bogs, visiting thistles and other flowers. One of the more common species, the great spangled fritillary, is found from Canada south to Georgia, New Mexico, and central California. The lesser fritillaries are small, swift fliers that range as far north as the Arctic.

Frog

Smooth-skinned, tailless creatures with bulging eyes and powerful hind legs adapted for leaping and swimming, frogs are the most familiar of our amphibians. They are found from the Arctic to the tropics, and range in size from tiny cricket frogs, sometimes a mere half inch long, to bassvoiced, eight-inch bullfrogs. Most have thin, moist skin and must live in or near water; others live on land but return to the water to breed.

In spring the males raucously summon the females with a variety of mating calls, each species sounding its own particular notes. After joining them in the water, the females lay eggs by the hundreds or even the thousands. Covered with a protective, jellylike coating, the fertilized eggs hatch into tadpoles a week to a month later. The tadpoles undergo an amazing transformation as they develop from long-tailed, round-bellied, gill-breathing larvae into tailless, strong-limbed, lung-breathing adults. Bullfrog tadpoles take up to three years to develop into frogs, but most species take just a few months. Although frogs begin life as vegetarians, they are voracious carnivores as adults. Skilled hunters, they devour huge quantities of insects, as well as spiders, earthworms, and other small creatures, which they catch with their long sticky tongues. Cold-blooded animals, many of the frogs hibernate in winter by burying themselves in mud at the bottom of ponds.

Frogfish

Plump, round-bodied inhabitants of warmwater seas, frogfish are intricately camouflaged anglers. They entice their prey-usually small fish-within range of their wide mouths by waving a wormlike lure from the end of their "fishing rod," actually a modified spine on the dorsal fin. Most frogfish rest quietly in place on the ocean floor or crawl about with the help of armlike pectoral fins. The sargassumfish, one of the best-known species, in contrast, lives not at the bottom of the sea but instead drifts near the surface amid floating forests of sargassum weed. Looking very much like the algae in which it dwells, it creeps among the plants, stalking other inhabitants of the sargassum weed. Sargassumfish have the ability to inflate their bodies by swallowing water or air, most likely as a means of preventing predators from extricating them from their seaweed world.

Froghopper

See Spittlebug.

Frond

A leaflike structure found in some lower plants.

Front

Associated with changing weather, a front is the moving boundary between two air masses of different properties. If the advancing air mass is colder than the one it is replacing, the leading edge of colder air is called a cold front; if the air is warmer, the leading edge is called a warm front. Cold fronts move rapidly, as the denser, heavier cold air drives a wedge under the warm air. Most cold fronts cause brief showers and gusty winds, followed by clear skies and cool, dry conditions. Warm fronts move more slowly, with the advancing warm air gradually sliding up over the heavier, low-lying cold air. They bring layered clouds and longer, steadier rains, which are usually followed by clearing skies and warm, humid air. When a fast-moving cold front catches up with a slowly advancing warm front, the result is an occluded front. The warm air, now surrounded by colder air, is forced aloft. Trapped over a trough of cool air, the warm air produces rain that lasts for hours.

Frost

The delicate ice crystals that tum grass to silvery white, create feathery patterns on windowpanes, and lend a magical quality to other surfaces are known as frost. It is formed-usually on cold, cloudless nights-when air saturated with moisture comes in contact with belowfreezing surfaces near the ground. Unlike frozen dew, which occurs when dewdrops freeze after a fall in temperature, frost is formed from water vapor that has crystallized directly into ice without passing through the liquid stage.

Fruit

Fruit are seeds together with their surrounding tissues. Botanically speaking, acorns, cucumbers, bean pods, and even grains of wheat all are fruits. The mature seed-bearing structures of flowering plants, fruits develop from the flowers' ovaries and, sometimes, associated floral parts. They can be sweet and fleshy, like apples and cherries, or dry and papery, like milkweed pods. Fruits are classified according to their structure. Simple fruits, for example, develop from a single ovary, while complex fruits derive from more than one. Those with stony pits, such as peaches and plums, are called drupes; pods, like those of peas and beans, are legumes; and the winged fruits of maples and elms are known as samaras. Apples and pears are called pomes; their edible flesh is actually swollen stem tissue. So is the ripe flesh of a strawberry; the seeds on its surface are in fact tiny individual fruits called achenes.

Fruit fly

Tiny insects that lay their eggs on fruit or decaying vegetation, fruit flies of various kinds are found all over the country. The Mediterranean fruit fly, for example, is a serious pest that periodically infests citrus crops. The well-known vinegar fly, Drosophila melanogaster, in contrast, has benefited humanity, for it has proved to be an ideal subject for the study of heredity.

Fulmar

Fulmarus glacialis

Stocky seabirds that look like thick-necked gulls, fulmars spend most of their lives gliding over far northern seas. They feed mainly on fish and squid but also trail fishing boats to scavenge for cast-off wastes. Like their relatives the petrels, fulmars have tubelike nostrils atop their beaks. When disturbed, they regurgitate a thick, smelly oil and spit it at enemies. The name fulmar, in fact, means foul gull.

Fumarole

Often hissing with steam, fumaroles are vents in the earth that emit water vapor, carbon dioxide, and other volcanic gases. They are found in volcanic areas such as Yellowstone National Park, where molten magma lies relatively close to the surface. The discharge from some fumaroles is mainly steam; in others the water vapor carries along a mixture of volatile, sometimes noxious, gases escaping from the lava.

Function

An Animal Behavior term, this is used to describe the function of an attribute, such as a behavior pattern, is its selective advAntage. This is the way in which it confers on its possessors greater survival and reproductive success than if they did not have it, and thereby persists in the population.

Functional response

The change in an individual predator's rate of exploitation of prey as a result of a change in prey density.

Funding (Action and Learning)

Money provided for a particular use. The government provides funding to a wide range of community groups and individuals to carry out projects aimed at protecting, conserving or restoring the environment.

Fungus

Molds, mildews, yeasts, and the familiar mushrooms all are fungi. Although they have traditionally been considered plants, fungi differ in so many ways that some scientists now place them in a separate kingdom. Unlike green plants, for example, fungi have no chlorophyll to make their own food and so must absorb nutrients from other organisms, living or dead. Most fungi are microscopic, but even those that yield mushrooms or other visible structures consist mainly of underground masses of fine cottony threads. A mushroom is the fungus's fruiting body and exists solely to make spores that, scattered by wind and water, develop into new fungi. Many of the fungi form partnerships with plants. Lichens, for instance, consist of algae and fungi that live in close association. Other fungi are attached to the roots of living plants, providing them with mineral nutrients and receiving food in return. Many plants, such as orchids, cannot survive without the help of fungi. Fungi also cause diseases, including ringworm, athlete's foot, and the rusts and smuts that afflict many crop plants. But mostly they are beneficial. Fungi enrich the soil by assisting in decay; they cause the fermentation that results in alcohol; they produce antibiotics and other life-saving drugs. And of course, many mushrooms are good to eat.

Gabbro

A dark, coarse-grained igneous rock, gabbro forms by slow cooling and crystallization of magma deep within the earth. Common in the Adirondack Mountains of New York, it often contains the green mineral olivine, as well as feldspar and large amounts of iron-rich minerals such as pyroxene. Sometimes sold under the name black granite, gabbro is widely used as a building stone, and it is especially popular for decorative facings.

Gaia Hypothesis

Biological Philosophy term. Gaia is the Greek godd