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Portal:Birds

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The Birds Portal

Eurasian nuthatch (Sitta europaea)

Birds are a group of warm-blooded vertebrate animals constituting the class Aves, 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 that retains dinosaur-like characteristics. 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 and they are split into 44 orders. More than half of the world's bird species are passerine or "perching" birds. Nearly all birds have wings whose development varies according to the life style of each species. 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 only known groups without wings are the extinct moa and elephant birds. Birds are the only extant members of Dinosauria, and are a type of paravian theropods. 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 evolved from earlier theropods, and thus constitute the only known living dinosaurs. Whilst traditional Linnaean taxonomy placed birds in their own class (owing to their unique morphology and being the only group of animals other than mammals where all its species are warm-blooded), birds are considered reptiles in the modern cladistic sense of the term. Their closest living relatives are the crocodilians, both forming a clade known as archosaurs. Birds are descendants of the primitive avialans (whose members include Archaeopteryx) which first appeared during the Late Jurassic. According to some estimates, modern birds (Neornithes) evolved in the Late Cretaceous or between the Early and Late Cretaceous (100 Ma) and diversified dramatically around the time of the Cretaceous–Paleogene extinction event 66 million years ago, which killed off the pterosaurs and all non-ornithuran dinosaurs.

Many social species preserve knowledge across generations (culture). Birds are social, communicating with visual signals, calls, and songs, and participating in such behaviour 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...)

Selected general bird topic

A diagram of a bird egg

A bird egg is the reproductive structure produced by female birds, consisting of a hard, calcareous shell that encloses nutrient-dense yolk, protective albumen, and embryonic membranes, providing a self-contained environment for embryonic development and hatching. Bird eggs 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...)

Selected taxon

Cathartidae, commonly known as New World vultures and 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 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 (Cathartes sp.) 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 which helps prevent rotting matter from accumulating while feeding, and an extremely disease-resistant digestive system to protect against dangerous pathogens found in decaying meat. (Full article...)

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Resources

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

Selected images

Selected bird anatomy topic

3 bursa of Fabricius opened : left : chronic inflamation; middle : acute inflamation; right : normal

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...)

Selected species

Elfin-woods warbler
The elfin-woods warbler (Dendroica angelae, Spanish: reinita de bosque enano), is a bird endemic to the Caribbean island of Puerto Rico where it is a local and uncommon species. It was discovered in 1968 and described in 1972. The species name, angelae, is a tribute to Angela Kepler, one of its discoverers. An insectivore, it feeds by gleaning small insects off leaves. Due to its small populations and restricted habitats, conservation efforts were begun in 1982 to protect this species. The species is not in immediate danger as the majority of its habitat is protected forest, but introduced species, such as rats and mongooses, habitat reduction, and natural disasters represent potential threats to the population.


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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Taxonomy of Aves

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Sources

  1. ^ Gaither, C.C.; Cavazos-Gaither, A.E. (2012). Gaither's Dictionary of Scientific Quotations. Springer New York. p. 1660. ISBN 978-1-4614-1114-7. Retrieved February 7, 2020.
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