Birds of humid Andean forests include mountain-toucans, quetzals and the Andean Cock-of-the-rock, while mixed species flocks dominated by tanagers and Furnariids commonly are seen-in contrast to several vocal but typically cryptic species of wrens, tapaculos and antpittas.

Birds ( class Aves ) are feathered, winged, bipedal, endothermic ( warm-blooded ), egg-laying, vertebrate animals.

Birds also have unique digestive and respiratory systems that are highly adapted for flight.

Birds are social ; they communicate using visual signals and through calls and songs, and participate in social behaviours, including cooperative breeding and hunting, flocking, and mobbing of predators.

Birds are bipedal when not flying.

Birds of prey, waterfowl, and song birds are more susceptible to eggshell thinning than chickens and related species, and DDE appears to be more potent than DDT.

He responded, " ' The Birds of America ' will then raise in value as much as they are now depreciated by certain fools and envious persons.

Birds adapted to living in the marine environment are often referred to as seabirds.

Birds, humans, insects, crustaceans, and snakes are not quadrupeds.

Birds from the western Pacific population are somewhat larger than those from the eastern Pacific, and male birds tend to be slightly larger than females.

Birds are thus equipped to fly at altitudes at which mammals would succumb to hypoxia.

Birds typically have a reverse, ZW system — males are ZZ and females ZW.

Birds, too, can see into the ultraviolet ( 300 – 400 nm ), and some have sex-dependent markings on their plumage that are visible only in the ultraviolet range.

Birds are also of medical importance and their role as carriers of human diseases such as Japanese Encephalitis, West Nile Virus and H5N1 have been widely recognised.

Birds have a similar system of sex determination ( ZW sex-determination system ), in which it is the females that are heterogametic ( ZW ), while males are homogametic ( ZZ ).

Birds of prey are birds that hunt for food primarily via flight, using their keen senses, especially vision.

Birds of prey generally prey on vertebrates, which are usually quite large relative to the size of the bird.

Under the Wild Birds Directive, 26 sites totalling roughly 25 % of the nation's land are " Special Protected Areas "; the Natura 2000 proposal would increase the totals to 260 sites and 32 % of national territory.

Under the classification used in the Handbook of the Birds of the World ( HBW ) main groupings of the sparrows are the true sparrows ( genus Passer ), the snowfinches ( typically one genus, Montifringilla ), and the rock sparrows ( Petronia and the Pale Rockfinch ).

Birds and other small wildlife are common throughout the grounds.

Some of the exhibits at the Bronx Zoo, such as World of Birds and World of Reptiles, are arranged by taxonomy, while others, such as African Plains and Wild Asia, are arranged geographically.

Birds, including parrots are plentiful.

The Thames Basin Heaths Special Protection Area ( SPA ), 1356 hectares of which lie within Bracknell Forest ( Sandhurst to Owlsmoor Bogs and Heaths SSSI and the Broadmoor to Bagshot Woods and Heaths SSSI ), supports nationally important populations of Dartford Warbler, Nightjar and Woodlark, all of which are Annex I species of the Birds Directive, and a small breeding population of Hobby, an important migratory species in a European context.

Others have been made into short films, often rewritten by other people, and even as feature length films, such is the case of Children of the Corn, The Birds, Brokeback Mountain, Who Goes There ?, Duel, A sound of thunder, The Body, The Lawnmower Man, and Hearts in Atlantis.

Birds often eat the egg-laden bodies of female bagworms after they have died.

Birds are also warm-blooded and are similar in size to many small mammals, yet often live 5 – 10 times as long.

Two of the subspecies listed above ( Falco peregrinus pelegrinoides and F. p. babylonicus ) are often instead treated together as a distinct species, Falco pelegrinoides ( Barbary Falcon ), although they were included within F. peregrinus in the 1994 Handbook of the Birds of the World.

Birds in coastal Portugal are also often listed as this subspecies but this is disputed.

Birds, insects, aircraft, and kites are often considered to fly in the sky.

Birds are generally of little importance however, except in spring when male songbirds are engaged in courtship display and often rather oblivious of their surroundings, in late summer when inexperienced fledglings abound, and in winter when most small mammals hibernate.

Birds breeding at the coast often make foraging flights to inland lakes or offshore areas to feed.

Notably, jazz bassist David Holland's album, which was written as a metaphor for his own enlightenment, and Om's Conference of the Birds, which deals with extremely esoteric themes often connected with metaphors of flight, inward vision, destruction of self, and oneness with the cosmos

Birds forage singly or in pairs in summer, and more often in larger flocks in autumn and winter, during which time they are more likely to loiter around people and urban areas.

Birds breeding in western Alaska winter along the Pacific coast from southern Alaska to California ; they often move inland – particularly to the rich feeding grounds in the Californian Central Valley – and some cross the Rocky Mountains again and winter as far east as Utah and south to Texas and northern Mexico.

Birds in their first year are often duller or a different color altogether.

Birds often hide their illnesses very well, and an avian veterinarian may see symptoms of illness that are not observable to the untrained eye.

Birds breeding in Ireland and western Scotland are slightly darker coloured than those in other areas, and are often distinguished as the subspecies Anthus pratensis whistleri, though it intergrades clinally with nominate Anthus pratensis pratensis found in the rest of the species ' range.

Birds may not breed for another year or two, and are often vagrants (" floaters ") until they establish their own territories.

Birds often nest at the edge of ponds / wetland complexes and travel large distances to feed at the waters edge.

Buyers who arrive before the hours of the sale to review the items are known as " Early Birds ;" they often are professional restorers or resellers.

Birds within a group often indulge in allopreening, play chases and mock fights.

Birds are often seen singly or in groups of up to three individuals, sometimes joining mixed-species foraging flocks.

Birds will often ascend slowly before making impressively steep parabolic dives ; it is thought that this behaviour is often associated with nesting, or nest failure.

The Common Nighthawk is one of more than 50 species of birds seen in the monument. Birds are the animals most often seen in the monument.

Birds are found often in Finnic mythology.