BIO 554/754

Terms to describe bird feet:

Anisodactyl: the hallux is behind and the other three toes are in front, as in a thrush.
Drawing of an anisodactyl foot
Syndactyl: the third and fourth toes (outer and middle) are united for most of their length and have a broad sole in common, as in the Belted Kingfisher 
See diagram below
Zygodactyl: the toes are arranged in pairs, the second and third toes in front, the fourth and hallux behind, as in a woodpecker.
Drawing of a zygodactyl foot
Heterodactyl: like the zygodactyl foot except the inner toe is reversed (digits 3 and 4 face forward, 1 and 2 face       backward); only found in trogons. 
See diagram below
Pamprodactyl: all four toes are in front
Although listed as a 'foot type' by Proctor and Lynch (1993:72), it is doubtful that ". . . any birds predominantly or even regularly use this toe configuration . . . " (Collins 1983:736).
Raptorial: the toes are deeply cleft, with large, strong, sharply curved nails (talons), as in hawks & owls
Drawing of a raptorial foot
Semipalmate, or half-webbed: the anterior toes are joined part way by a small webbing, as in the Semipalmated Plover
Drawing of a semipalmate foot
Totipalmate, or fully webbed:  all four toes are united by ample webs, as in a cormorant.
Drawing of a totipalmate foot
Palmate, or webbed: the front toes are united as in ducks and gulls.
Lobate, or lobed: a swimming foot with a series of lateral lobes on the toes, as in a grebe. 

Drawings of the different types of bird feet

Toe arrangements: a = anisodactyl, b = zygodactyl, c = heterodactyl, d =  syndactyl, & e =  pamprodactyl (as illustrated in Proctor and Lynch 1993, but see Collins 1983).

Literature Cited:

Collins, C.T. 1983. A reinterpretation of pamprodactyly in swifts: a convergent grasping mechanism in vertebrates. Auk 100:735-737.

Proctor, N.S. and P.J. Lynch. 1993. Manual of ornithology: avian structure and function. Yale Univ. Press, New Haven.

Useful links:

Topography of the Foot

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