Feet and Legs
Birds stand completely on their toes. Their instep, or tarsus, is elevated, and the angle at which the leg bends forward (which looks like a backward “knee”) is actually the bird's “heel.” The bird's knee (the top of what we call the “drumstick”) is hidden in feathers. Like a knee, it bends forward when the bird squats.
There is wide speciation among birds as to the number and arrangement of toes. Whereas their reptilian ancestors had five toes, most birds today have four toes, as described in the discussion of the bird's skeleton earlier.
Songbirds and perching birds (this includes over 50 percent of all birds) have a back-turned first toe (hallux). We call this first toe by the Roman numeral ‘I,’ and the subsequent toes ‘II,’ ‘III,’ and ‘IV.’ If it is at the same level as the other toes, as it is predominantly, the hallux is incumbent. The feet of many ground-dwelling birds have an elevated hallux that does not touch the ground.
Brief descriptions (followed by images) of the basic toe configurations follow:
Tridactyl feet. Birds such as Sanderlings have three toes.
Didactyl feet. The ostrich, for example, has two toes.
Pamprodactyl feet. Swifts, for example, are capable of turning all toes forward.
Syndactyl feet. The kingfisher, for example, has two toes fused for part of their length.
Zygodactyl feet. Two outside toes (I and IV) face backward as on the parrot. These birds are also called “yoke-toed.”
Anisodactyl feet. The first toe faces backward. An example is the robin.
Heterodactyl feet. Two toes (I and II) face backward, two forward for example on the trogon.
Palmate feet. Webbing connects the three front toes. An example is the Mallard.
Totipalmate feet. Webbing connects all four toes as on the pelican.
Lobate feet. Membranous lobes increase the size of the toes for swimming and keep the bird (such as the coot) from sinking in mud.
In identifying birds, decide whether the bird is flat footed or has a nice arch. Water birds have flat toes for wading and swimming. Birds that spend time in trees have curly toes.
Bird claws, which we call talons on birds of prey, are formed by scales at the end of each toe. The scales grow and fall off continuously. Some birds use them for climbing and scratching the ground for food, others for seizing prey. Birds of prey use their talons to tear off bits of flesh. They can feed their nestlings morsels as small as match-sticks.
In winter, many grouse and ptarmigans grow a horny fringe along the sides of their toes. This functions like a snowshoe, which they then slough in the spring. Various birds have a toothed surface on one claw that they use for grooming rictal bristles around the beak and removing parasites from their feathers. This is the feather comb.
Assorted pheasants, turkeys, and other fowl sport bony outgrowths with hard, pointed horns growing from the rear inner tarsus. Birds use these spurs to fight during breeding season in the spring. A few species may actually kill each other with their spurs.
Other differences distinguish bird species’ feet from one another. For instance, a wading bird called a jacana has disproportionately elongated toes that prevent it from sinking. Although it is actually balancing on vegetation, it appears to be walking on water. While most birds’ legs and feet are bare, owls’ are feathered. This adaptation muffles the sound of owls’ stealthy approach.