Birds are feathered, winged, bipedal, endothermic, egg-laying, vertebrate animals. About ten,000 residing species makes them one of the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the world, through the Arctic for the Antarctic. Extant birds selection in dimension from the five cm Bee Hummingbird to your 2.seventy five m Ostrich. The fossil document signifies birds advanced from theropod dinosaurs through the Jurassic period of time, all around 160 million a long time ago. Paleontologists regard birds since the only clade of dinosaurs to have survived the Cretaceous?¡ìCPaleogene extinction occasion 65.five Ma ago.
Present day birds are characterised by feathers, a beak with no teeth, the laying of hard-shelled eggs, a substantial metabolic pace, a four-chambered heart, plus a light-weight but robust skeleton. All dwelling species of birds have wings?athe now extinct flightless Moa of New Zealand was the sole exception. Wings are evolved forelimbs, and most bird species can fly, with some exceptions, like ratites, penguins, and a number of diverse endemic island species. Birds also have special digestive and respiratory techniques which can be highly adapted for flight. Some birds, especially corvids and parrots, are amongst one of the most intelligent animal species; several bird species are already observed production and using equipment, and many social species exhibit cultural transmission of know-how across generations.
Lots of species undertake extensive length yearly migrations, and lots of far more complete shorter irregular movements. Birds are social; they talk making use of visual indicators and by calls and songs, and take part in social behaviours, together with cooperative breeding and hunting, flocking, and mobbing of predators. The vast greater part of bird species are socially monogamous, typically for one breeding year at a time, from time to time for years, but almost never for everyday living. Other species have polygynous or, rarely, polyandrous breeding techniques. Eggs are generally laid inside of a nest and incubated with the mothers and fathers. Most birds have an prolonged time period of parental care just after hatching.
A lot of species are of financial value, primarily as sources of meals acquired by hunting or farming. Some species, notably songbirds and parrots, are popular as pets. Other uses contain the harvesting of guano for use being a fertiliser. Birds figure prominently in all facets of human culture from religion to poetry to popular songs. About 120?¡ìC130 species are getting to be extinct as a result of human activity because the 17th century, and hundreds additional in advance of then. Presently about 1,200 species of birds are threatened with extinction by human things to do, although efforts are underway to guard them.