greylag, (Anser anser), most common Eurasian representative of the so-called gray goose and ancestor of all Occidental domestic geese. It belongs to the subfamily Anserinae, family Anatidae (order Anseriformes). It nests in temperate regions and winters from Britain to North Africa, India, and China. The greylag is pale gray in colour, with pink legs; the bill is pink in the eastern race, orange in the western.