Portal:Birds

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The Birds Portal

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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Sign marking the borders of the bird reserve at Ågestasjön, Sweden
A bird reserve (also called ornithological reserve) is a wildlife refuge designed to protect bird species. Like other wildlife refuges, the main goal of a reserve is to prevent species from becoming endangered or extinct. Typically, bird species in a reserve are protected from hunting and habitat destruction. Because of the protection they provide from such threats, bird reserves also serve as excellent locations for bird watching. Normally, wildlife refuges are under the care of non-profit organizations and governmental institutions. (Full article...)
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Rufous whistler (Pachycephala rufiventris)
The Pachycephalidae are a family of bird species that includes the whistlers, shrikethrushes, and three of the pitohuis, and is part of the ancient Australo-Papuan radiation of songbirds. The family includes 64 species that are separated into five genera. Its members range from small to medium in size, and occupy most of Australasia. Australia and New Guinea are the centre of their diversity and, in the case of the whistlers, the South Pacific islands as far as Tonga and Samoa and parts of Asia as far as India. The exact delimitation of boundaries of the family are uncertain, and one species, the golden whistler, has been the subject of intense taxonomic scrutiny in recent years, with multiple subspecies and species-level revisions. (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.

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Secarecytosis is a process involved in the development of a bird's lung cells, before the bird hatches from its egg. It is the processes of cell cutting during attenuation of the tubular epithelium of the developing avian lung. The word secarecytosis is derived from the Latin word secare which means "to cut".

Secarecytosis differs from holocrine and apocrine secretory mechanisms in that it occurs only during development and that portions of cells, complete with their organelles, are lost. It has three documented phenotypes. These are:

  • formation of a double cell membrane and separation between the two membranes;
  • formation of large vacuoles in the supranuclear cytoplasm, their subsequent fusion with each other and with the lateral cell membranes thus separating the apical portion;
  • formation of many tiny vesicles that fuse with each other and the cell membrane thus severing portions of the cell. (Full article...)
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King vulture
The king vulture, Sarcoramphus papa, is a large Central and South American bird in the New World vulture family Cathartidae. This vulture lives predominantly in tropical lowland forests stretching from southern Mexico to northern Argentina. It is the only surviving member of the genus Sarcoramphus, though fossil members are known. It is large and predominantly white, with gray to black ruff, flight, and tail feathers. Its head and neck are bald, with the skin color varying, including yellow, orange, blue, purple, and red. The king vulture has a very noticeable yellow fleshy carnucle on its beak. This vulture is a scavenger and it often makes the initial cut into a fresh carcass. It also displaces smaller New World vulture species from a carcass. King vultures were popular figures in the Mayan codices as well as in local folklore and medicine. Though currently listed as being of least concern by the IUCN, they are declining in number, due primarily to habitat loss.


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Taxonomy of Aves

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Sources

  1. ^ Platt, S.; Library of Congress (1993). Respectfully Quoted: A Dictionary of Quotations. Barnes & Noble Books. p. 242. ISBN 978-0-88029-768-4. Retrieved February 7, 2020.
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