The Swan Goose is 81–94 cm (32–37 in) long (the longest Anser goose) and weighing 2.8–3.5 kg (6.2–7.7 lb) or more. The sexes are similar, although the male is larger. 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.
Is a rare large goose with a natural breeding range in inland Mongolia, northernmost China, and southeastern Russia.This species has been domesticated. Introduced and feral populations of its domestic breeds occur in many places outside its natural range.
There is a family of these geese living in the garden and pond of Arenberg Kasteelpark in Heverlee. Very tame, sweet and always on the lookout for the more than occasional scrapes of bread offered by passer-bys.