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 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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A diagram of a bird egg
Bird eggs are laid by the females and range in quantity from one (as in condors) to up to seventeen (the grey partridge). Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been fertilized; it is not uncommon for pet owners to find their lone bird nesting on a clutch of infertile eggs, which are sometimes called wind-eggs. (Full article...)
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Cathartidae, known commonly as New World vultures or condors, are a family of birds of prey consisting of seven extant species in five genera. It includes five extant vultures and two extant condors found in warm and temperate areas of the Americas. They are known as "New World" vultures to distinguish them from Old World vultures, with which the Cathartidae does not form a single clade despite the two being similar in appearance and behavior as a result of convergent evolution.

Like other vultures, New World vultures are scavengers, having evolved to feed off of the carcasses of dead animals without any notable ill effects. Some species of New World vulture have a good sense of smell, whereas Old World vultures find carcasses exclusively by sight. Other adaptations shared by both Old and New World vultures include a bald head, devoid of feathers to prevent rotting matter from accumulating while feeding, and an extremely disease-resistant digestive system to protect against scavenging-related germs. (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.

WikiProjects

  • WikiProject Birds
  • WikiProject Science
  • WikiProject History of Science
  • WikiProject Tree of Life
  • WikiProject Biology
  • WikiProject Ecology
  • WikiProject Extinction

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In birds, the bursa of Fabricius (Latin: bursa cloacalis or bursa fabricii) is the site of hematopoiesis. It is a specialized organ that, as first demonstrated by Bruce Glick and later by Max Dale Cooper and Robert Good, is necessary for B cell (part of the immune system) development in birds. Mammals generally do not have an equivalent organ; the bone marrow is often the site of both hematopoiesis and B cell development. The bursa is present in the cloaca of birds and is named after Hieronymus Fabricius, who described it in 1621. (Full article...)
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A male splendid fairy-wren (subsp. splendens)
The splendid fairy-wren (Malurus splendens), also known simply as the splendid wren or more colloquially in Western Australia as the blue wren, is a passerine bird of the family Maluridae. It is found across much of the Australian continent from central-western New South Wales and southwestern Queensland over to coastal Western Australia. The male in breeding plumage is a small, long-tailed bird of predominantly bright blue and black colouration. Non-breeding males, females and juveniles are predominantly grey-brown in colour. It comprises several similar all-blue and black subspecies that were originally considered separate species. Like other fairy-wrens, the splendid fairy-wren is notable for several peculiar behavioural characteristics; birds are socially monogamous and sexually promiscuous. Male wrens pluck pink or purple petals and display them to females as part of a courtship display. The habitat of the splendid fairy-wren ranges from forest to dry scrub, generally with ample vegetation for shelter. It has not adapted well to human occupation of the landscape and has disappeared from some urbanized areas. The splendid fairy-wren mainly eats insects and supplements its diet with seeds.


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Taxonomy of Aves

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Sources

  1. Hudson, William Henry (1998). Green Mansions. Oxford, UK: Oxford University Press. p. 63. ISBN 0-19-283-288-3.
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