ecology: Methods in ecology: Biotelemetry and other electronic tracking equipment, which allow the movements and behaviour of free-ranging organisms to be followed remotely, can provide rapid sampling of populations. Radioisotopes are used for tracing the pathways of nutrients through ecosystems, for determining the time and extent of transfer of…

ecoterrorism: …of terrorism, also known as bioterrorism, includes, for example, threats to contaminate water supplies or to destroy or disable energy utilities, as well as practices such as the deployment of anthrax or other biological agents.

angiosperm: Distribution and abundance: …and their almost complete worldwide distribution. The only area without angiosperms is the southern region of the Antarctic continent, although two angiosperm groups are found in the islands off that continent. Angiosperms dominate terrestrial vegetation, particularly in the tropics, although submerged and floating aquatic angiosperms do exist throughout the world.…

community ecology: Guilds and interaction webs: Most communities contain groups of species known as guilds, which exploit the same kinds of resources in comparable ways. The name “guild” emphasizes the fact that these groups are like associations of craftsmen who employ similar techniques in plying their trade. Guilds may…

biotic potential, the maximum reproductive capacity of an organism under optimum environmental conditions. It is often expressed as a proportional or percentage increase per year, as in the statement “The human population increased by 3 percent last year.” It can also be expressed as the time it

biogeographic region: Endemism: …can be quantified using Jaccard’s coefficient of biotic similarity, which is determined by the equation:

biotin, water-soluble, nitrogen-containing acid essential for growth and well-being in animals and some microorganisms. Biotin is a member of the B complex of vitamins. It functions in the formation and metabolism of fats and carbohydrates. A relatively stable substance, it is widely distributed in

biotite, a silicate mineral in the common mica group. It is abundant in metamorphic rocks (both regional and contact), in pegmatites, and also in granites and other intrusive igneous rocks. For chemical formula and detailed physical properties, see mica (table). Biotite is regarded as a mixture

Cobán: …Cobán in nearby Purulhá is Biotopo del Quetzal. This cloud forest and nature reserve dedicated to preserving Guatemala’s national bird, the quetzal, is open for tourists. The agricultural hinterland of Cobán is best known for its coffee, tea, cacao (the source of cocoa beans), vanilla, cardamom and other spices. Grains,…

toxin, any substance poisonous to an organism. The term is sometimes restricted to poisons spontaneously produced by living organisms (biotoxins). Besides the poisons produced by such microorganisms as bacteria, dinoflagellates, and algae, there are toxins from fungi (mycotoxins), higher plants

poison: Biotransformation: Biotransformation, sometimes referred to as metabolism, is the structural modification of a chemical by enzymes in the body. Chemicals are biotransformed in several organs, including the liver, kidneys, lungs, skin, intestines, and placenta, with the liver being the most important. Chemicals absorbed in the…

Cambrian Period: Fauna: …fossils indicates changes in Cambrian bioturbation, the churning and stirring of seafloor sediment by animal forms. Late Precambrian (Ediacaran) trace fossils from around the world are essentially surface trails that show little evidence of sediment burrowing. Quantitative study in the western United States has shown that a significant increase in…

Adolfo Bioy Casares was an Argentine writer and editor, known both for his own work and for his collaborations with Jorge Luis Borges. His elegantly constructed works are oriented toward metaphysical possibilities and employ the fantastic to achieve their meanings. Born into a wealthy family, Bioy

biozone, stratigraphic unit consisting of all the strata containing a particular fossil and, hence, deposited during its existence. The extent of the unit in a particular place, on the local stratigraphic range of the fossil plant or animal involved, is called a teilzone. The geological time units

pipa: …the contemporary pipa is the quxiang (“curved-neck”) pipa, which traveled from Persia by way of the Silk Road and reached western China in the 4th century ad. It had a pear-shaped wooden body with two crescent-shaped sound holes, a curved neck, four strings, and four frets. In performance it was…

United States: The Iran nuclear deal, the Bipartisan Budget Act of 2013, and the Ukraine crisis: …the Senate (64–36) passed the Bipartisan Budget Act of 2013, based on a compromise forged by Republican Rep. Paul Ryan and Democratic Sen. Patty Murray, the chairpersons of the House and Senate Budget Committees, respectively. The act replaced the bulk of the automatic spending cuts required by sequestration with targeted

Bipartisan Campaign Reform Act of 2002 (BCRA), U.S. legislation that was the first major amendment of the Federal Election Campaign Act of 1971 (FECA) since the extensive 1974 amendments that followed the Watergate scandal. The primary purpose of the Bipartisan Campaign Reform Act (BCRA) was to

Joe Biden: Presidency: …the Senate passed the bipartisan Infrastructure Investment and Jobs Act, a drastically scaled-back ($550 billion) version of a wide-ranging infrastructure plan announced by Biden in March. Its smaller scale was made necessary by objections from Republicans and conservative Democrats to spending levels, tax increases on corporations and the wealthy, and…

marine ecosystem: Distribution and dispersal: …many marine organisms is a bipartite life cycle, which can affect the dispersal of an organism. Most animals found on soft and hard substrata, such as lobsters (see Figure 4), crabs, barnacles, fish, polychaete worms, and sea urchins, spend their larval phase in the plankton and in this phase are…

mammal: The female tract: Carnivores have a bipartite uterus, in which the horns are largely separate but enter the vagina by a single cervix. In the bicornate uterus, typical of many ungulates, the horns are distinct for less than half their length; the lower part of the uterus is a common chamber,…

bipedalism, a major type of locomotion, involving movement on two feet. The order Primates possesses some degree of bipedal ability. All primates sit upright. Many stand upright without supporting their body weight by their arms, and some, especially the apes, actually walk upright for short

lizard: Annotated classification: Amphisbaenia Family Bipedidae (two-legged worm lizards) Worm lizards with front limbs that are molelike. 1 genus, Bipes, is known and contains 3 species. Restricted to western Mexico and Baja California. Family Amphisbaenidae (worm lizards) Limbless, wormlike lizards that are found through much of the tropical world but are…

Peter Seeberg: …first book appeared in 1956, Bipersonerne (“Secondary Characters”), a novel about a collective of foreign workers in Berlin toward the end of World War II. These workers inhabit an unreal world, a film studio, at an unreal time, and their alienation gradually becomes symbolic of the human condition in general.…

biphenyl, an aromatic hydrocarbon, used alone or with diphenyl ether as a heat-transfer fluid; chemical formula, C6H5C6H5. It may be isolated from coal tar; in the United States, it is manufactured on a large scale by the thermal dehydrogenation of benzene. Biphenyl is slightly less reactive

Coleoptera: Annotated classification: Family Biphyllidae (false skin beetle) About 200 species; mostly tropical; example Biphyllus. Family Byturidae (fruitworm beetles) Small, hairy; few genera; damage raspberry blossoms and fruit; example Byturus. Family Cerylonidae

echinoderm: Development: …of asteroids develops into a bipinnaria larva with two ciliated bands, which also may become sinuous and form lobes or arms; one band lies in front of the mouth, the other behind it and around the edge of the body. In most asteroids the larval form in the next stage…

biplane, airplane with two wings, one above the other. In the 1890s this configuration was adopted for some successful piloted gliders. The Wright brothers’ biplanes (1903–09) opened the era of powered flight. Biplanes predominated in military and commercial aviation from World War I through the

angiocardiography: …frequently used angiocardiographic methods are biplane angiocardiography and cineangiocardiography. In the first method, large X-ray films are exposed at the rate of 10 to 12 per second in two planes at right angles to each other, thus permitting the simultaneous recording of two different views.

International Bureau of Weights and Measures (BIPM), international organization founded to bring about the unification of measurement systems, to establish and preserve fundamental international standards and prototypes, to verify national standards, and to determine fundamental physical constants.

photoreception: Neural transmission: …rear of the retina, the bipolar cells, and finally the ganglion cells, whose axons make up the optic nerve. Forming a network between the photoreceptors and the bipolar cells are the horizontal cells (the outer plexiform layer), and between the bipolar cells and the ganglion cells, there exists a similar…

human ear: Auditory nerve fibres: …longer central processes of the bipolar cochlear neurons unite and are twisted like the cords of a rope to form the cochlear nerve trunk. These primary auditory fibres exit the modiolus through the internal meatus, or passageway, and immediately enter the part of the brainstem called the medulla oblongata.

bipolar disorder, mental disorder characterized by recurrent depression or mania with abrupt or gradual onsets and recoveries. There are several types of bipolar disorder, in which the states of mania and depression may alternate cyclically, one mood state may predominate over the other, or they

bipolar disorder: …disorder, which encompass the so-called bipolar spectrum, include bipolar I, bipolar II, mixed bipolar, and cyclothymia.

semiconductor device: Bipolar transistors: This type of transistor is one of the most important of the semiconductor devices. It is a bipolar device in that both electrons and holes are involved in the conduction process. The bipolar transistor delivers a change in output current in response to…

propellant: …ignited by some external means; bipropellants, consisting of an oxidizer such as liquid oxygen and a fuel such as liquid hydrogen, which are injected into a combustion chamber from separate containers; and multipropellants, consisting of several oxidizers and fuels.

building-integrated photovoltaics (BIPVs), photovoltaic cells and thin-film solar cells that are integral components of a building. Building-integrated photovoltaics (BIPVs) simultaneously serve conventional structural functions—as exteriors, windows, or rooftops—while also generating electricity.

Bekaa valley, broad valley of east-central Lebanon, extending in a northeast-southwest direction for 75 miles (120 km) along the Litani and Orontes rivers, between the Lebanon Mountains to the west and Anti-Lebanon Mountains to the east. The valley contains nearly half of Lebanon’s arable land but

Lodovico Ferrari: …solution to the biquadratic, or quartic, equation (an algebraic equation that contains the fourth power of the unknown quantity but no higher power).

William Kingdon Clifford: Clifford developed the theory of biquaternions (a generalization of the Irish mathematician Sir William Rowan Hamilton’s theory of quaternions) and then linked them with more general associative algebras. He used biquaternions to study motion in non-Euclidean spaces and certain closed Euclidean manifolds (surfaces), now known as “spaces of Clifford-Klein.” He…

Beed, city, central Maharashtra state, western India, on a tributary of the Krishna River near a gap in a range of low hills. Beed was known earlier as Champavatinagar. Its other name, Bir or Bhir, probably was derived from the Persian bhir (“water”). In its early history it belonged to the

Sait Faik Abasıyanık: …also wrote an experimental novel, Bir takım insanlar (1952; “A Group of People”), which was censored because it dealt strongly with class differences.

symmetry: Symmetry in animals: In biradial symmetry, in addition to the anteroposterior axis, there are also two other axes or planes of symmetry at right angles to it and to each other: the sagittal, or median vertical-longitudinal, and transverse, or cross, axes. Such an animal therefore not only has two…

Birāk, oasis, western Libya, on the southeastern edge of Al-Ḥamrāʾ Hammada, a stony plateau. One of the string of oases along the Wādī (seasonal river) ash-Shāṭiʾ, it is isolated from Sabhā, 40 mi (64 km) south, by great sand dunes, but the Adīrī-Birāk road, running east, links with the north road

Tall Birāk, ancient site located in the fertile Nahr al-Khābūr basin in Al-Ḥasakah governorate, Syria; it was inhabited from c. 3200 to c. 2200 bc. One of the most interesting discoveries at Birāk was the Eye Temple (c. 3000), so named because of the thousands of small stone “eye idols” found

crustacean: Appendages: …or from the double-branched (biramous) limb of the class Remipedia. A biramous limb typically has a basal part, or protopodite, bearing two branches, an inner endopodite and an outer exopodite. The protopodite can vary greatly in its development and may have additional lobes on both its inner and outer…

Marie-François-Pierre Maine de Biran was a French statesman, empiricist philosopher, and prolific writer who stressed the inner life of man, against the prevalent emphasis on external sense experience, as a prerequisite for understanding the human self. Born with the surname Gonthier de Biran, he

Berar, cotton-growing region, east-central Maharashtra state, western India. The region extends for approximately 200 miles (320 km) east-west along the Purna River basin and lies 700 to 1,600 feet (200 to 500 metres) above sea level. Berar is bounded on the north by the Gawilgarh Hills (Melghat)

Birātnagar, town, southeastern Nepal, in the Terai, a low, fertile plain, north of Jogbani, India. The town is Nepal’s principal industrial and foreign trade centre; manufactures include jute, sugar, and cotton. The Birātnagar Jute Mills (1936) was Nepal’s first industrial endeavour and became one

Philae, island in the Nile River between the old Aswan Dam and the Aswan High Dam, in Aswān muḥāfaẓah (governorate), southern Egypt. Its ancient Egyptian name was P-aaleq; the Coptic-derived name Pilak (“End,” or “Remote Place”) probably refers to its marking the boundary with Nubia. The

Bīrbal was a Brahman courtier of the Mughal emperor Akbar. With a reputation as a skilled poet and a charismatic wit, he joined Akbar’s court early in the emperor’s reign and became one of his closest advisers. Indeed, Bīrbal was the only Hindu follower of Akbar’s elite religious movement, the

Birbhum, district, West Bengal state, northeastern India. It comprises two distinct regions. To the west lies an undulating, generally barren upland, part of the eastern fringe of the Chota Nagpur plateau, rising to 3,000 feet (900 metres); to the east is a densely populated alluvial plain of the

Ira Glass: …frequent This American Life contributor) Mike Birbiglia. Glass also was a producer on Birbiglia’s film Don’t Think Twice (2016), which was about a New York City improv comedy troupe.

amidah: …sections and is known as bircath sheva. The 13 petitions are omitted because it is forbidden to speak of need and sadness at these joyous services.

birch, (genus Betula), genus of about 40 species of short-lived ornamental and timber trees and shrubs of the family Betulaceae, distributed throughout cool regions of the Northern Hemisphere. A birch has smooth, resinous, varicoloured or white bark, marked by horizontal pores (lenticels), which

Birch and Swinnerton-Dyer conjecture, in mathematics, the conjecture that an elliptic curve (a type of cubic curve, or algebraic curve of order 3, confined to a region known as a torus) has either an infinite number of rational points (solutions) or a finite number of rational points, according to

sweet birch: Birch beer is made from the sap.

Betulaceae, family of six genera and about 145 species of woody flowering plants (order Fagales). Members of the family are distributed in temperate and subarctic areas of the Northern Hemisphere, where some reach the northern limit of woody plants; in tropical mountains; and in South America

Polyporales: The inedible birch fungus Polyporus betulinus causes decay on birch trees in the northern United States. Dryad’s saddle (P. squamosus) produces a fan- or saddle-shaped mushroom. It is light coloured with dark scales, has a strong odour, and grows on many deciduous trees. The edible hen of…

birch mouse, (genus Sicista), any of 13 species of small, long-tailed mouselike rodents. Birch mice live in the northern forests, thickets, and subalpine meadows and steppes of Europe and Asia. Their bodies are 5 to 10 cm (2 to 4 inches) long, excluding the semiprehensile tail that is longer than

sweet birch: …birch is a source of birch oil, formerly a substitute for oil of wintergreen, and is used in aromatherapy. Birch beer is made from the sap.

Birch and Swinnerton-Dyer conjecture: …1960s in England, British mathematicians Bryan Birch and Peter Swinnerton-Dyer used the EDSAC (Electronic Delay Storage Automatic Calculator) computer at the University of Cambridge to do numerical investigations of elliptic curves. Based on these numerical results, they made their famous conjecture.

Perak War: …assassination in 1875 of James Birch, the first British resident (adviser) in Perak. Although they succeeded in eliminating Birch, the Malay leaders failed in their ultimate objective—the curbing of British economic and political influence in the area.

John Birch Society: The name derives from John Birch, an American Baptist missionary and U.S. Army intelligence officer who was killed by Chinese communists on Aug. 25, 1945, making him, in the society’s view, the first hero of the Cold War. The society publishes the biweekly magazine The New American and the…

Grease: Legacy: … (1982), which is directed by Patricia Birch (who served as the choreographer for Grease and its original stage production) and stars Michelle Pfeiffer. Grease also inspired the musical television series Grease: Rise of the Pink Ladies (2023), which is set four years before the events in Grease.

American Beauty: …unhappy teenage daughter, Jane (Thora Birch). Lester also hates his job. Lester and Carolyn go to a basketball game at Jane’s high school to see Jane perform with the other cheerleaders, and Lester becomes thoroughly infatuated with another cheerleader, Jane’s friend Angela (Mena Suvari), to Jane’s horror. Angela, however,…

mountain mahogany: Common species: The birch-leaf mountain mahogany (Cercocarpus betuloides) and curl-leaf mountain mahogany (C. ledifolius) are both scaly-barked trees that may reach up to 9 metres (30 feet) in height. The true, or alder-leaf, mountain mahogany (C. montanus) is a long-lived shrub common to the foothills of the Rocky…

corporate governance: Johnston Birchall, a British professor in social policy, argued that it is useful to focus on three main issues when considering how organizations are governed. The first issue concerns which individuals or groups are provided with membership rights. Membership rights might be given only to…

canoe: The birchbark canoe was first used by the Algonquin Indians in what is now the northeastern part of the United States and adjacent Canada, and its use passed westward. Such canoes were used for carrying goods, hunters, fishermen, and warriors. The craft varied in length from…

Louise Erdrich: Birchbark Books and other literary works: …stories, and children’s books, including The Birchbark House (1999), which launched a series: The Game of Silence (2005), The Porcupine Year (2008), Chickadee (2012), and Makoons (2016). Her memoir The Blue Jay’s Dance: A Birth Year (1995) is a meditation on her experience of pregnancy, motherhood, and writing. In 2026…

Sabi River: …by the 1,080-foot (329-meter) single-span Birchenough Bridge, 83 miles (133 km) south of Mutare (formerly Umtali), just north of its confluence with the Devure River. The river is navigable by light craft for 100 miles (160 km) above its mouth.

John Banville: Fiction: …an intentionally ambiguous narrative, and Birchwood (1973), the story of an aristocratic Irish family in decline. Doctor Copernicus (1976), Kepler (1981), and The Newton Letter: An Interlude (1982) are fictional biographies based on the lives of noted scientists. These three works use scientific exploration as a metaphor to question perceptions…

Charlie Parker was an American alto saxophonist, composer, and bandleader. He was a lyric artist generally considered the greatest jazz saxophonist. Parker was the principal stimulus of the modern jazz idiom known as bebop, and—together with Louis Armstrong and Ornette Coleman—he was one of the

Jackson Pollock: Early life and work: …paintings from this period include Bird (c. 1941), Male and Female (c. 1942), and Guardians of the Secret (1943).

Barry Keoghan: Star turns: The Banshees of Inisherin and Saltburn: …two children in the drama Bird; and an Irish shepherd in the thriller Bring Them Down. The following year he appeared as a manager for a musician (played by the artist known as the Weeknd) in the thriller Hurry Up Tomorrow. In 2026 he was part of the ensemble cast…

Clint Eastwood: First directorial efforts: …Eastwood also directed the well-regarded Bird (1988), a film biography of saxophonist Charlie Parker (Forest Whitaker), and produced the documentary Thelonious Monk: Straight, No Chaser (1988). Off-screen, Eastwood made national headlines in 1986 when he was elected mayor of Carmel, California; he served for two years.

badminton: …with lightweight rackets and a shuttlecock. The roots of the sport can be traced to the old game battledore and shuttlecock, which was played in ancient Greece, China, and India. The game was taken from India to England, where it was first played in Gloucestershire, at the country estate of…

bird, (class Aves), any of the approximately 11,200 living species unique in having feathers, the major characteristic that distinguishes them from all other animals. A more-elaborate definition would note that they are warm-blooded vertebrates more related to reptiles than to mammals and that they

Rosa Guy: Guy’s first novel, Bird at My Window (1966), is set in Harlem and examines the relationship between black mothers and their children, as well as the social forces that foster the demoralization of black men. Children of Longing (1970), which Guy edited, contains accounts of black teens’ and…

ornithology: Bird banding (or ringing), first performed early in the 19th century, is now a major means of gaining information on longevity and movements. Banding systems are conducted by a number of countries, and each year hundreds of thousands of birds are marked with numbered leg bands.…

Sandra Bullock: Later work: …a perilous journey blindfolded in Bird Box, a supernatural thriller in which an obscure force causes destruction to those who look upon it. In her next film, The Unforgivable (2021), Bullock portrayed a convicted murderer who searches for redemption and her younger sister after being released from prison. She returned…

bird rug, floor covering woven in western Turkey, carrying on an ivory ground a repeating pattern in which leaflike figures, erroneously described as birds, cluster around stylized flowers. The rugs first appear in Western paintings in the 16th century and were probably not woven after the 18th

Marie Ponsot: …poetry: The Green Dark (1988), The Bird Catcher (1998; National Book Critics Circle Award), Springing: New and Selected Poems (2002), and Collected Poems (2016).

John T. McCutcheon: …fictional Illinois town he called Bird Center. The series, continued when he joined the Chicago Tribune in 1903, stressed the wholesome values of small-town life. A collection of the Bird Center cartoons was published in 1904. Three years after joining the Tribune he was sent on a tour of Asia.…

Annie Proulx: In the memoir Bird Cloud (2011), Proulx chronicled the building of her home in Wyoming.

chemoreception: Smell: When bird dogs are searching for a scent on the ground, they may sniff very rapidly, perhaps creating turbulence of the air in the nasal cavity and enhancing the likelihood that odor molecules will reach the olfactory epithelium. When these dogs run into the wind with…

immune system disorder: Type III hypersensitivity: …fungal spores from moldy hay; pigeon fancier’s lung, resulting from proteins from powdery pigeon dung; and humidifier fever, caused by normally harmless protozoans that can grow in air-conditioning units and become dispersed in fine droplets in climate-controlled offices. In each case, the person will be sensitized to the antigen—i.e., will…

Derek Jacobi: He later was cast in A Bird Flew In (2021), a drama that follows various characters as they endure a lockdown during the COVID-19 coronavirus pandemic.

angiosperm: Pollination: Vertebrate pollinators include birds, bats, small marsupials, and small rodents. Many bird-pollinated flowers are bright red, especially those pollinated by hummingbirds. Hummingbirds rely solely on nectar as their food source. Flowers (e.g., Fuchsia) pollinated by birds produce copious quantities of nectar but little or no odor because birds

bird flu, a viral respiratory disease mainly of poultry and certain other bird species, including migratory waterbirds, some imported pet birds, and ostriches, that can be transmitted directly to humans. The first known cases in humans were reported in 1997, when an outbreak of avian influenza A

coffee: Grading: … certification and the Smithsonian Institution’s Bird Friendly certification are awarded to sustainable shade-grown coffee that protects biodiversity.

Constantin Brancusi: Maturity of Constantin Brancusi: …of polished-bronze sculptures, all entitled Bird in Space. The elliptical, slender lines of these figures put the very essence of rapid flight into concrete form.

Kenneth Rexroth: Later writings and other projects: His essays include Bird in the Bush (1959), Assays (1962), The Alternative Society (1970), With Eye and Ear (1970), and American Poetry in the Twentieth Century (1971). An Autobiographical Novel was published in 1966. Shortly before his death from heart disease in 1982, Rexroth converted to

Seychelles: Plant and animal life: Bird Island is the breeding ground for millions of terns, turtle doves, shearwaters, frigate birds, and other seabirds that flock there each year.

Bird Island, coral-covered sandbank only 15 feet (4.5 metres) high at low tide, located in the Caribbean Sea about 350 miles (560 km) north of Venezuela and 70 miles (110 km) west of Dominica. (The island is not a part of the group of Venezuelan islands of similar name, Islas de Aves, comprising

bird louse, (suborder Amblycera and Ischnocera), any of two groups of chewing lice (order Phthiraptera) that live on birds and feed on feathers, skin, and sometimes blood. Probably all bird species have these chewing lice. Although they are not harmful, if they become too numerous, their irritation

avian malaria, infectious disease of birds that is known particularly for its devastation of native bird populations on the Hawaiian Islands. It is similar to human malaria in that it is caused by single-celled protozoans of the genus Plasmodium and is transmitted through the bite of infected

Trinidad and Tobago: Little Tobago lies about a mile off Tobago’s northeastern coast. Also called Bird of Paradise Island, Little Tobago was once noted as the only wild habitat of the greater bird of paradise outside of New Guinea; however, the bird is no longer found there.

bird of prey, any bird that pursues other animals for food; it is a famous apex predator (meaning without a natural predator or enemy). Birds of prey are classified in two orders: Falconiformes and Strigiformes. All birds of prey have hook-tipped beaks and sharp curved claws called talons (in

Goldie Hawn: …who became her longtime companion; Bird on a Wire (1990), with Mel Gibson; Housesitter (1992), with Steve Martin; Robert Zemeckis’s dark comedy Death Becomes Her (1992), with Meryl Streep and Bruce Willis; and The First Wives Club (1996), with

aviary, a structure for the keeping of captive birds, usually spacious enough for the aviculturist to enter. Aviaries range from small enclosures a metre or so on a side to large flight cages 30 m (100 feet) or more long and as much as 15 m high. Enclosures for birds that fly only little or weakly