Birds

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There are about 10 thousand living types, more than half of which will be passerine, or "perching" birds. Birds possess wings whose growth varies according to species; the sole known groups with out wings would be the vanished moa and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although more evolution has brought to the loss of trip in some wild birds, including ratites, penguins, and diverse native to the island island species. The digestive and respiratory systems of birds are also distinctly adapted for airline flight. Some bird types of aquatic conditions, particularly seabirds and some waterbirds, include further evolved with regard to swimming.

Birds happen to be descendants of the primitive avialans (whose members include Archaeopteryx) which first appeared about 160 mil years ago (mya) in China. In accordance with 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 sixty six mya, which slain off the pterosaurs and all non-avian dinosaurs.

Many social kinds pass on knowledge across generations, which is usually considered a kind of traditions. Birds are cultural, communicating with visual signals, calls, plus songs, and participating in such behaviours because cooperative breeding and hunting, flocking, and even mobbing of predators. The vast bulk of bird species are socially (but not necessarily sexually) monogamous, usually for one breeding time at a moment, sometimes for decades, but rarely intended for life. Other types have breeding systems that are polygynous (one male together with many females) or perhaps, rarely, polyandrous (one female with many males). Birds produce children by laying ova which are fertilised through sexual reproduction. They are generally laid inside a nest and incubated by the parents. Most birds have an extended period of parental care after hatching