The mute swan, Cygnus olor, is raised in captivity for its great beauty; domesticated birds are frequently seen on small lakes in parks and private grounds. The male, or cob, in particular, is an impressive sight when disturbed: he pulls his S-curved neck on to his back and raises his bent wings to make himself appear larger. Full-grown adult birds may weigh as much as 22 lb. The adult bird has white plumage and an orange bill with a black knob. The young (cygnets) are grey-brown.

Wild populations may be found here and there in northern Europe and discontinuously throughout central Asia to the lower reaches of the Amur River in eastern Asia. In the United States, feral mute swans, descendants of birds escaped from captivity, are fairly common in the coastal areas of the middle Atlantic states. The mute swan occupies some of the same habitats as the whooper swan, the two species sometimes nesting together. The nest is built in reeds or on islets by the female (pen), with material supplied by the cob.