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
Emu in Australia at the time of European settlement, and one additional species is known from fossil remains. The insular dwarf emus, "D. baudinianus" and "D. n. minor", originally present on Kangaroo Island and King Island respectively, both became extinct shortly after the arrival of Europeans. "D. n. diemenensis", a subspecies known as the Tasmanian emu, became extinct around 1865. However, the mainland sub-species, "D. n. novaehollandiae", remains common. The population of these birds varies from decade to decade, largely being dependent on rainfall; in 2009, it was estimated that there were between 630,000 and 725,000 birds. Emus were introduced to