This classification is based primarily on that of the American ornithologist Alexander Wet.... order present;

Gliding birds, about 50 cm long. Order Lower Eocene to present; South America. Order ( Lower Pliocene to present (the Eocene Eleutherornis may belong here); southwestern Asia and Africa (fossils from southern Europe and southeastern Asia). Largest living bird; length to 180 cm, height 260 cm, weight 136 kg, egg 1.6 kg. Order Pleistocene; Madagascar (upper Eocene and lower Oligocene fossils from Egypt have been placed here). Very large (to 3 m tall) and graviportal birds (moas) or smaller (length 3080 cm); almost wingless, nocturnal, probing birds (kiwis). Order (pelicans, boobies, tropic birds, cormorants, frigate birds) Paleocene to present; worldwide. Web-footed birds with broad bills containing fine plates or lamellae (waterfowl); or large-footed marsh birds with chicken-like bills (screamers). Order (herons, storks, ibises, spoonbills) Upper Cretaceous to present; worldwide except in extreme north. Order Upper Paleocene to present; worldwide. Diurnal raptors with hooked ! beaks, long talons, and short (hawks, falcons) or very long (secretary bird) legs or carrion-eating birds with weaker claws and tear-ing bills (vultures, condors). Order (grouse, pheasants, quail, turkeys) Middle Eocene to present; nearly worldwide, except southern South America. Order (cranes, rails, coots, cariamas, bustards) Upper Cretaceous to present; worldwide. Length 11152 cm (fossils to 200 cm tall). Order (plovers, sandpipers, gulls, terns, auks) Upper Cretaceous to present; worldwide. 3 basic body plans: Suborder Charadriiwaders (shorebirds), usually feeding on small animals in mud or water, bill variable but often long and used for probing; Lariweb-footed, dense-plumaged water birds feeding by plunging into water for fish, robbing other birds, or scavenging; Alcaedense-plumaged, web-footed, marine, wing-propelled divers, feeding on fish or invertebrates. Order (sand grouse, pigeons, doves, dodoes) Upper Eocene or lower Oligocene to present; worldwide except in ex! treme north. Order (parrots, lories, cockatoos) Upper Oligocen! e to present; throughout tropics, with some temperate-zone species. Order (turacos, cuckoos, roadrunners) Upper Eocene or lower Oligocene to present; worldwide except in extreme north. Order (nightjars, frogmouths, oilbird) Pliocene to present; worldwide except in extreme north. Order (swifts, hummingbirds) Upper Eocene or lower Oligocene to present; worldwide except in extreme north; hummingbirds limited to New World. Order Pantropical, except Australasia; upper Eocene or lower Oligocene to present. Order Eocene to present; worldwide except in extreme north. Order (woodpeckers, barbets, honey guides, toucans) Upper Oligocene (possibly upper Eocene) to present. Order Upper Eocene to present; worldwide. The large complex assemblage of perching birds, containing more than half of the known species of birds. order present;