Portal:Birds

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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 over 11,000 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 recent estimates, modern birds (Neornithes) evolved in the Late Cretaceous and diversified dramatically around the time of the Cretaceous–Paleogene extinction event 66 million years ago, 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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With forward-facing eyes, the bald eagle has a wide field of binocular vision.

Vision is the most important sense for birds, since good eyesight is essential for safe flight. Birds have a number of adaptations which give visual acuity superior to that of other vertebrate groups; a pigeon has been described as "two eyes with wings". Birds are theropod dinosaurs, and the avian eye resembles that of other sauropsids, with ciliary muscles that can change the shape of the lens rapidly and to a greater extent than in the mammals. Birds have the largest eyes relative to their size in the animal kingdom, and movement is consequently limited within the eye's bony socket. In addition to the two eyelids usually found in vertebrates, bird's eyes are protected by a third transparent movable membrane. The eye's internal anatomy is similar to that of other vertebrates, but has a structure, the pecten oculi, unique to birds.

Some bird groups have specific modifications to their visual system linked to their way of life. Birds of prey have a very high density of receptors and other adaptations that maximise visual acuity. The placement of their eyes gives them good binocular vision enabling accurate judgement of distances. Nocturnal species have tubular eyes, low numbers of colour detectors, but a high density of rod cells which function well in poor light. Terns, gulls, and albatrosses are among the seabirds that have red or yellow oil droplets in the colour receptors to improve distance vision especially in hazy conditions. (Full article...)
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Green wood hoopoe (Phoeniculus purpureus) at Marakele National Park, South Africa

The wood hoopoes or scimitarbills are a small African family, Phoeniculidae, of near passerine birds. They live south of the Sahara Desert and are not migratory. While the family is now restricted to Sub-Saharan Africa, fossil evidence shows that it once had a larger distribution. Fossils attributed to this family have been found in Miocene rocks in Germany.

The wood hoopoes are related to the kingfishers, the rollers, and the hoopoe, forming a clade with this last according to Hackett et al. (2008). A close relationship between the hoopoe and the wood hoopoes is also supported by the shared and unique nature of their stapes. The wood hoopoes most resemble the true hoopoes with their long down-curved bills and short rounded wings. According to genetic studies, the two genera, Phoeniculus and Rhinopomastus, appear to have diverged about ten million years ago, so some systematists treat them as separate subfamilies or even separate families. (Full article...)
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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.

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Grandry corpuscles are found in high numbers in the bills of aquatic birds, such as ducks, where they are believed to play a role in feeding.
The tactile corpuscles of Grandry or Grandry corpuscles are mechanoreceptors found in the beak skin and oral mucosa of aquatic birds. They were first described by Grandry in 1869 in the bill skin of ducks and geese. Their general structure includes the flattened endings of an afferent nerve fiber sandwiched between two or more somewhat flattened sensory cells called Grandry cells, all surrounded by a layer of satellite cells and a partial capsule of collagen protein. Electrophysiological studies have shown that Grandry corpuscles function as rapidly adapting velocity detectors. In birds, Grandry and Merkel corpuscles share many morphological similarities, which has led to some confusion in the literature over their classification (see §Grandry and Merkel corpuscles). (Full article...)
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A red-tailed black cockatoo in flight
The red-tailed black cockatoo (Calyptorhynchus banksii), also known as Banksian- or Bank's black cockatoo, is a large cockatoo native to Australia. It is more common in the drier parts of the continent. Five subspecies are recognised, differing most significantly in beak size. Although the more northerly subspecies are widespread, the two southern subspecies, the forest red-tailed black cockatoo and the south-eastern red-tailed black cockatoo are under threat. Adult red-tailed black cockatoos are around 60 centimetres (24 in) in length and sexually dimorphic. Males are completely black in colour, excepting their prominent red tail bands; the slightly smaller females are brownish-black with yellow barring and spotting and have yellow-orange tail stripes. The species is usually found in eucalyptus woodlands, or along water courses. In the more northerly parts of the country, these cockatoos are commonly seen in large flocks. They are seed eaters and cavity nesters. Of the black cockatoos, the red-tailed black is the most adaptable to aviculture, although black cockatoos are much rarer and much more expensive outside Australia.


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Taxonomy of Aves

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Sources

  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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