Swans usually mate for life, though "divorce" does sometimes occur, particularly following nesting failure. The number of eggs in each clutch varies both within and among swan species, typically between 3-8 eggs.
Young swans are known as cygnets, from the Latin word for swan, cygnus. The male and female adults are known as cob and pen, though these terms are little used nowadays.
The Northern Hemisphere species of swan are all pure white in plumage, but the Southern Hemisphere species are all patterned with various amounts of black. The Australian Black Swan (Cygnus atratus) is blackest, black all over except for the white flight feathers on its wings, and the South American Black-necked Swan has, as its name suggests, a black neck; finally, the Coscoroba Swan, also from southern South America, has black tips to the primary feathers. The legs of all swans are dark blackish grey, except for the two South American species, which have pink legs. Bill colour varies rather more; the three far northern species have black bills with varying amounts of yellow, and all the others varyingly patterned red and black. The Mute Swan and Black-necked Swan have a curious lump at the base of the bill on the upper mandible.
Species of swan:
Once swans were considered an edible form of poultry. Nowadays they are protected species in many countries. In Britain, for example, all swans are protected by law. However, they may be taken for food under some circumstances, and roast swan is a traditional item at celebratory dinners in certain Oxbridge colleges.
The noise a swan makes is uniquely known as a "beable", but this word has fallen into disuse in all but a few parts of Britain.
Cygnus, the Swan, is also a constellation in the northern sky.