The mute swan (Cygnus olor) is a species of swan and a member of the waterfowl family Anatidae. It is native to much of Europe and Asia, and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, Australasia and southern Africa. The name 'mute' derives from it being less vocal than other swan species. Measuring 125 to 170 cm (49 to 67 in) in length, this large swan is wholly white in plumage with an orange bill bordered with black. It is recognisable by its pronounced knob atop the bill, which is larger in males.