Birds

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There are about eight thousand living kinds, more than 1 / 2 of which happen to be passerine, or "perching" birds. Birds have got wings whose growth varies according to species; the sole known groups without wings will be the vanished moa and dickhäuter (umgangssprachlich) birds. Wings, which evolved from forelimbs, gave birds to be able to fly, although even more evolution has led to losing airline flight in some parrots, including ratites, polar bears, and diverse native to the island island species. The digestive and respiratory systems of parrots are also exclusively adapted for air travel. Some bird kinds of aquatic environments, particularly seabirds in addition to some waterbirds, have further evolved for swimming.

Birds are descendants of typically the primitive avialans (whose members include Archaeopteryx) which first appeared about 160 , 000, 000 years ago (mya) in China. According to DNA evidence, modern day birds (Neornithes) advanced in the Midst to Late Cretaceous, and diversified considerably around the time of the Cretaceous? Paleogene extinction event 66 mya, which murdered off the pterosaurs and everything non-avian dinosaurs.

Many social species spread knowledge around generations, which is considered a form of traditions. Birds are sociable, communicating with visual signals, calls, and even songs, and taking part in such behaviours while cooperative breeding in addition to hunting, flocking, in addition to mobbing of potential predators. The vast majority of bird species are socially (but not necessarily sexually) monogamous, usually with regard to one breeding season at a time, sometimes for decades, but rarely intended for life. Other varieties have breeding techniques that are polygynous (one male along with many females) or perhaps, rarely, polyandrous (one female numerous males). Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are generally laid in the home and incubated by simply the parents. Most birds have a great extended period of parental care after hatching