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Birds are a group of warm-blooded vertebrates constituting the class Aves (/ˈvz/), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5.5 cm (2.2 in) bee hummingbird to the 2.8 m (9 ft 2 in) common ostrich. There are about ten thousand living species, more than half of which are passerine, or "perching" birds. Birds have wings whose development varies according to species; the only known groups without wings are the extinct moa and elephant birds. Wings, which are modified forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in some birds, including ratites, penguins, and diverse endemic island species. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming. The study of birds is called ornithology.

Birds are feathered theropod dinosaurs and constitute the only known living dinosaurs. Likewise, birds are considered reptiles in the modern cladistic sense of the term, and their closest living relatives are the crocodilians. Birds are descendants of the primitive avialans (whose members include Archaeopteryx) which first appeared during the Late Jurassic. According to DNA evidence, modern birds (Neornithes) evolved in the Early to Late Cretaceous, and diversified dramatically around the time of the Cretaceous–Paleogene extinction event 66 mya, which killed off the pterosaurs and all non-avian dinosaurs.

Many social species pass on knowledge across generations, which is considered a form of culture. Birds are social, communicating with visual signals, calls, and songs, and participating in such behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially (but not necessarily sexually) monogamous, usually for one breeding season at a time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (one male with many females) or, rarely, polyandrous (one female with many males). Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching.

Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs, meat, and feathers. Songbirds, parrots, and other species are popular as pets. Guano (bird excrement) is harvested for use as a fertiliser. Birds figure throughout human culture. About 120 to 130 species have become extinct due to human activity since the 17th century, and hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry. (Full article...)

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Selected general bird topic

African jacana. Extremely long toes and claws help distribute the jacana's weight over a wide area to allow it to walk on floating leaves.

The anatomy of bird legs and feet is diverse, encompassing many accommodations to perform a wide variety of functions.

Most birds are classified as digitigrade animals, meaning they walk on their toes rather than the entire foot. Some of the lower bones of the foot (the distals and most of the metatarsal) are fused to form the tarsometatarsus – a third segment of the leg, specific to birds. The upper bones of the foot (proximals), in turn, are fused with the tibia to form the tibiotarsus, as over time the centralia disappeared. The fibula also reduced. (Full article...)
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Selected taxon

White-winged chough (Corcorax melanorhamphos)
Corcoracidae is a family of passerine birds known as the Australian mudnesters. The family has sometimes been called Struthideidae in the past; however, despite Struthideidae being an older name than Corcoracidae, the latter name takes precedence. It contains just two species in two genera, the white-winged chough (Corcorax melanorhamphos) and the apostlebird (Struthidea cinerea). Both are endemic to Australia. (Full article...)
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Free online resources:

There is also Birds of North America, Cornell University's massive project collecting information on every breeding bird in the ABA area. It is available for US$40 a year.

For more sources, including printed sources, see WikiProject Birds.


Selected images

Selected bird anatomy topic

Columella (highlighted) in the skull of the extinct therapsid Dicynodon.
In the auditory system, the columella contributes to hearing in amphibians, reptiles and birds. The columella form thin, bony structures in the interior of the skull and serve the purpose of transmitting sounds from the eardrum. It is an evolutionary homolog of the stapes, one of the auditory ossicles in mammals. In many species, the extracolumella is a cartilaginous structure that grows in association with the columella. During development, the columella is derived from the dorsal end of the hyoid arch. (Full article...)
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Selected species

California condor
The California condor, Gymnogyps californianus, is a species of North American bird in the New World vulture family Cathartidae. Currently, this condor inhabits only the western coastal mountains of the United States, Baja California, and the Grand Canyon. It is the only surviving member of the genus Gymnogyps, though fossil members are known. It is a large, black vulture with patches of white on the underside of the wings and a largely bald head with skin color ranging from yellowish to a glowing red, depending on the bird’s mood. It has the largest wingspan of any bird found in North America and is one of the heaviest. The condor is a scavenger and eats large amounts of carrion. Condor numbers dramatically declined in the 20th century. A conservation plan was put in place by the United States government that led to the capture of all the remaining wild condors in 1987. Beginning in 1991, condors have been reintroduced into the wild. The California condor is one of the world's rarest bird species. As of 2005, there were only 273 individuals including 127 in the wild.

Did you know

  • ...that sexual size dimorphism in the brown songlark is among the most pronounced in any bird, with males as much as 2.3 times heavier than females?
  • ...that rufous whistler birds, unlike all other whistler birds, never forage on the ground but high up in trees or other high places?
  • ...that the bill of the magpie duck (pictured) becomes green as the bird gets older, and its black crown may go completely white?


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More outstanding tasks at the project's cleanup listing, Category:Birds articles needing attention, and Wikipedia:WikiProject Birds/Todo.

Taxonomy of Aves

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  1. ^ Commons, T.K. (2012). Instant Genius: Smart Mouths: The Best Quotations Ever Collected. Portable Press. p. pt56. ISBN 978-1-60710-684-5. Retrieved February 7, 2020.
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