In birds normally called tarsus; the part of the leg from ankle to toes, in which most (foot)bones are fused to one tarsometatarsus. See also: leg and toe.
Three main types of bird feet can be recognised
1) Perching. This type has great holding and grasping power and can be of the passerine (all toes are free and mobile and the hind toe is highly developed and 'opposable' to produce a firm grip), zygodactyl (2 opposable toes) or the raptorial (widely spread toes with sharp, curved claws) form.
2) Walking and wading. This type has lost its gripping power and the hind toe has often become elevated to lose contact with the ground and/or is reduced in size or completely lost. In some wading birds the toes are (partially) webbed.
3) Swimming. In general this type is transformed to function like a paddle with the toes webbed. In the lobate variation each toe carries independent webs (e.g., the coots Fulica spp.), while in the palmate variation the 3 forward toes are united by a large web (e.g. gulls and ducks) and the hind toe is free and poorly developed. In the totipalmate variation (typical of the Pelecaniformes), all 4 toes are webbed to provide a perfect swimming foot. For examples, see Introduction.

Alternative forms for foot : feet, palmate, tarsus, totipalmate, web, webbed.