The Swan Goose is a rare large goose with a natural breeding range in inland Mongolia, northernmost China, and southeastern Russia. It is migratory and winters mainly in central and eastern China.
The Swan Goose is large and long-necked for its genus. It is 90cm long [the longest goose] and weighing 4kg OR more. The sexes are similar, although the male is larger, with a proportionally longer bill and neck. Wing Span is 45 cm; the bill is about 95 mm long. The upperparts are greyish-brown, with thin light fringes to the larger feathers and a maroon hindneck and cap reaching just below the eye. The remiges are blackish, as are the entire underwing and the white-tipped rectrices, while the upper- and undertail coverts are white. A thin white stripe surrounds the bill base. Apart from darker streaks on the belly and flanks, the underside is pale buff, being especially light on the lower head and foreneck which are sharply delimited against the maroon. In flight, the wings appear dark, with no conspicuous pattern. Uniquely among its genus, the long, heavy bill is completely black; the legs and feet, on the other hand, are orange as in most of its relatives. The eyes' irides are maroon.