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
Bird feet and legs absent in diving birds. For example, in the long-tailed duck, the leg and wing bones are not pneumatic, in contrast with some of the other bones, while loonsand puffins have even more massive skeletons with no aired bones. The flightless ostrich and emu have pneumatic femurs, and so far this is the only known pneumatic bone in these birds except for the ostrich's cervical vertebrae. Fusions (leading to rigidity) and pneumatic bones (leading to reduced mass) are some of the many adaptations of birds for flight. Most birds, except loons and grebes, are digitigrade, not plantigrade. Also, chicks in the