swan, common name for a large aquatic bird of both hemispheres, related to ducks and geese. It has a long, gracefully curved neck and an extremely long, convoluted trachea which makes possible its far-carrying calls. The orange-billed white trumpeter swan, Cygnus buccinator, seen in parks, is the mute swan, of Old World origin. It breeds in the wild state in parts of Europe, Asia, and the United States. During the breeding season it has a trumpetlike note, softer in the tame birds. The whistling swan migrates from the arctic to Mexico. Conservation measures saved the almost extinct trumpeter swan of North America, the largest species. Wild species in Europe include the whooper (or whooping) and the Bewick swans. The black swan, Chenopis atrata, is native to Australia, and the black-necked swan, Cygnus melancoriphus, to South America. The black swan has been domesticated. Swans are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Anseriformes, family Anatidae.
See study by P. Scott and the Wildfowl Trust (1972).