Birds
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There are about 10 thousand living species, more than 50 percent of which are usually passerine, or "perching" birds. Birds include wings whose enhancement varies according to be able to species; the just known groups with out wings will be the wiped out moa and elefant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although even more evolution has guided to the loss of trip in some wild birds, including ratites, polar bears, and diverse native to the island island species. The particular digestive and respiratory system systems of chickens are also uniquely adapted for air travel. Some bird types of aquatic environments, particularly seabirds plus some waterbirds, include further evolved intended for swimming.
Birds will be descendants of typically the primitive avialans (whose members include Archaeopteryx) which first appeared about 160 million years ago (mya) in China. According to DNA evidence, modern day birds (Neornithes) evolved in the Center to Late Cretaceous, and diversified considerably around the time of the Cretaceous? Paleogene extinction event 66 mya, which wiped out off the pterosaurs and everything non-avian dinosaurs.
Many social types spread knowledge around generations, which will be considered a sort of traditions. Birds are interpersonal, communicating with aesthetic signals, calls, plus songs, and participating in such behaviours while cooperative breeding in addition to hunting, flocking, in addition to mobbing of predators. The vast bulk of bird species are socially (but not necessarily sexually) monogamous, usually for one breeding period at a moment, sometimes for decades, but rarely regarding life. Other species have breeding methods that are polygynous (one male together with many females) or, rarely, polyandrous (one female numerous males). Birds produce children by laying eggs which are fertilised through sexual imitation. They are normally laid within a call home and incubated by the parents. Many birds have a good extended period associated with parental care right after hatching
