Anser cygnoides; Print; The swan goose (Anser cygnoides) is a 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. Vagrant birds are encountered in Japan and Korea (where it used to winter in numbers when it was more common); and more rarely in Kazakhstan; Laos; coastal Siberia; Taiwan; Thailand and Uzbekistan.; 1864-1915