There are seven species of swan in the genus Cygnus; this includes the Whistling Swan (Cygnus columbianus columbianus) and Bewick’s Swan (Cygnus columbianus bewickii) as sister species which are sometimes grouped together as Tundra Swan. The Coscoroba Swan (Coscoroba coscoroba) is the eight species and has physical features more closely aligned to a goose.
Five of the swan species are found in the Northern Hemisphere, these being the Whooper (Cygnus cygnus), Mute (Cygnus olor), Bewick’s, Whistling and the Trumpeter (Cygnus buccinators); all are white in colour. The southern hemisphere swans are a mix of colouration with the Black Swan (Cygnus atratus), the Black-necked Swan (Cygnus melanocoryphus) and the white Coscoroba.
Swans tend to pair for life and stay together throughout the year. There are a few exceptions, with occasional incidences of divorce. Mates have been observed to switch in all species if there has been a significant nesting failure or if the mate has been lost. Pairing for life holds many benefits, from raising clutches and learning opportunities for the young to mutual protection. Pairing for life is especially beneficial to the Bewick’s Swan which migrates an average 2,500 km a year, reducing available time for pairing and breeding.
The Whooper, Tundra and Trumpeter Swans are fully migratory species, whereas the Mute Swan is a partial migrant, being resident in Western Europe but migratory in Eastern Europe and Asia. The Black Swan is purely resident.
Swans primarily feed on aquatic vegetation, using their feet in shallow waters to expose roots and shoots. They feed by upending and plunging their heads into the water. Their long necks give them the advantage to feed in deeper waters than most other waterfowl, reducing the competition for food. In winter months where aquatic food sources are limited, swans will also eat grasses and cereal crops. Young cygnets will eat aquatic insects and crustaceans as they require more protein in their younger years.
Due to their large size, swans have few natural predators, their main threat is human activity; either in the form of degradation/destruction of habitat, hunting and lead poisoning following the ingestion of lead fishing weights and spent lead gunshot.