Bustard (Otis Tarda). issued in 28 July, 2003. The Great Bustard, Otis tarda, is in the bustard family, the only member of the genus Otis. It breeds in southern and central Europe, where it is the largest species of bird, and across temperate Asia. European populations are mainly resident, but Asian birds move further south in winter. Sizeable populations exist in Hungary, Portugal, Slovakia, Russia and Spain, but the species is declining due to habitat loss throughout its range. The male of this huge bird is possibly the heaviest extant bird capable of flight, alongside the similarly sized Kori Bustard. An adult male typically is 90-110 cm (3-3.7 ft) long with a 2.1-2.5 m (6.9-8.2 ft) wingspan and usually weighs from 10 to 16 kg (22-35 lb).[1] The heaviest known bird was about 21 kg (46 lb), although larger specimens have been reported but not verified. An adult male is brown above and white below, with a long grey neck and head. The breast and lower neck sides are chestnut. In the breeding season, the male has long white neck bristles. In flight, the long wings show large areas of white. The female is 30% smaller (typically 80 cm in length and 1.8 m across the wings) and one-third the weight of the male, averaging 3.5-5 kg (6-11 lb). Perhaps because of this, there is a slewed sex ratio of about 1.5:1 female to male. The breast and neck of the female are buff. Both sexes are usually silent. Immature birds resemble the female.