Flightless bird Flightless bird Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species including the well known ratites (ostrich, emu, cassowary, rhea and kiwi) and penguins. The smallest flightless bird is the Inaccessible Island rail (length 12.5 cm, weight 34.7 g). The largest (both heaviest and tallest) flightless bird, which is also the largest living bird, is the ostrich (2.7 m, 156 kg). Ostriches are farmed for their decorative feathers, meat and their skins, which are used to make leather. Many domesticated birds, such as the domestic chicken and domestic duck, have lost
Largest prehistoric animals "Argentavis magnificens" which a wingspan of , and a body weight of . The largest-known waterfowl of all time belonged to the Dromornithidae (e.g. "Dromornis stirtoni"). The largest-known of Ciconiiformes was "Leptoptilos robustus", standing tall and weighing an estimated . The largest-known of the hesperornithines was "Canadaga arctica" at long. The largest-known diatryma was "Gastornis" tall, with large individuals up to tall. The largest-known teratorn and the largest flying bird ever was "Argentavis". The immense bird had a wingspan estimated up to and a weight up to . It was as high as an adult human when standing. The largest-known-ever