The Probert Encyclopaedia of Nature

SWAN

The swan (Cygnus) is a genus of large, long necked birds of the goose sub- family (Anscrinae) of the duck family (Anatidae). They differ from geese in the bill being of equal breadth throughout and furnished with a knob at the base; medial nostrils; short legs and a very long neck. The commonest species seen in Britain is the mute swan, although the Whooper Swan and the Bewick's Swan also visit.
Research Swan