Birds

                 Birds (class Aves) are feathered, winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. With around 10,000 living species, they are the most speciose class of tetrapod vertebrates. All present species belong to the subclass Neornithes, and inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich. The fossil record indicates that birds emerged within theropod dinosaurs during the Jurassic period, around 160 million years (Ma) ago.
                The subclass Neornithes has two extant superorders: Palaeognathae. and Neognathae. The Palaeognathae consists of two orders which comprise 49 existing species: Struthioniformes (ostriches, emus, kiwis, and allies) and Tinamiformes (tinamous). Neognathae comprises 27 orders which have a total of nearly ten thousand species. The orders comprising the Neognathae are: Anseriformes (waterfowl), Galliformes (fowl), Charadriiformes (gulls, button-quails, plovers and allies), Gaviiformes (loons), Podicipediformes (grebes), Procellariiformes (albatrosses, petrels, and allies), Sphenisciformes (penguins),Pelecaniformes (pelicans and allies), Phaethontiformes (tropicbirds), Ciconiiformes (storks and allies), Cathartiformes (New World vultures), Phoenicopteriformes (flamingos), Falconiformes (falcons, eagles, hawks and allies), Gruiformes (cranes and allies), Pteroclidiformes (sandgrouse), Columbiformes (doves and pigeons), Psittaciformes (parrots and allies), Cuculiformes (cuckoos and turacos), Opisthocomiformes (hoatzin), Strigiformes (owls), Caprimulgiformes (nightjars and allies), Apodiformes (swifts and hummingbirds), Coraciiformes (kingfishers and allies), Piciformes (woodpeckers and allies), Trogoniformes (trogons), Coliiformes (mousebirds), Passeriformes (passerines).

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