Flightless birds are
birds that have evolved the inability to
fly. There are over 40 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.