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 organisms the giant moa ("Dinornis maximus"), part of the moa family of New Zealand that went extinct around 1500 AD. This particular species of moa stood up to tall, but weighed about half as much as a large elephant bird or mihirung due to its comparatively slender frame. The heaviest bird ever capable of flight was "Argentavis magnificens", the largest member of the now extinct family Teratornithidae, found in Miocene-aged fossil beds of Argentina, with a wingspan up to , a length of up to , a height on the ground of up to and a body weight of at least