Footsies

Great Egret feet_HomosassaSP-FL_LAH_8290

When out in the field identifying birds, how often do we look at the feet? For me, at least, the bird’s feet may be the last thing I take note of—if I can see them at all. Wading and swimming birds keep their feet under water and out of sight, and mind. Perched birds’ feet are often hidden in the foliage, or too small to see from a distance. Yet, bird feet can provide a clue, not just to a bird’s identity, but also to its habitat, diet, and general lifestyle.

Most bird species have four toes. In the majority of bird species, the “big toe” is turned toward the rear, while the other three face forward. You can see this in the photo at the top of the page. However, there are endless variations on this theme.

Birds tiptoe (they walk on their toes), which means they are considered “digitigrades” (so are cats and dogs, and many other animals). Loons and grebes are the exception—they walk on their metatarsals as well as their toes, like we do. This makes them “plantigrades” (I think of them “planting” their entire foot on the ground).

The “Thick-Knees,” such as this Bush Stone-Curlew, are named for what look like knobby knees. However, if you look at the skeleton, what we consider knees are actually ankles, so the bird family should actually be called “Thick-Ankles”!

Bush Stone-Curlew_LonePineKoalaSanctuary-Brisbane-QLD-Australia_LAH_1913

Birds of prey have strong, grasping talons tipped with sharp claws. Osprey even have spines on their soles, handy when you consider how hard it is to hold onto a wet fish!

Ptarmigans have feathery “snowshoes.”

Most birds have legs and feet that are the same color, but a glimpse of its “golden slippers” cinches the identity of a Snowy Egret. (A Snowy Egret look-alike on the other side of the world, Little Egrets have the same black legs and yellow feet combo, making it difficult to ID the rare stray.)

Snowy Egret_MerrittIslandNWR-FL_LAH_3570-001

Chickens, emus, and other ground-dwelling birds have tough feet with sharp claws used to scratch the dirt. Although they have the typical four toes, cranes, rails, and pheasants have their first toe higher up on their leg, where it won’t drag as they walk or run along the ground.

Sandhill Cranes_BosquedelApacheNWR-NM_LAH_7389

Cassowaries have three toes. The middle one is tipped with a dangerous claw that can be five inches long. The birds use it to defend themselves against potential predators.

Cassowary_DaintreeWildZoo-QLD-Australia_LAH_4987

Ostriches are unique in having their digits fused into two toes. Their feet mimic a horse’s hooves—perfect for long-distance running.

Ducks, loons, and gulls have palmate feet, with webbing between the three forward toes. On the other hand, the toes of some other water-going species all face forward, with webbing between all four digits. Examples of this arrangement include pelicans, cormorants, frigatebirds, and gannets.

Double-crested Cormorant_LaJollaCove-CA_LAH_0809

Shorebirds, especially those who typically walk on soft mud or sand, have some webbing, but not as much as ducks. Instead, their long toes spread their weight over a large surface. The jacanas take this to an extreme, as they scamper over floating waterlily leaves!

Grebes and coots have lobate feet. Instead of webbing, their toes and thick and fleshy. They get less propulsion than birds with webbing (there’s a reason swim fins are webbed, not lobate!), but it doesn’t seem to cause them any problems, and they can walk more easily on land this way. (Have you ever tried walking in fins?)

American Coot_Agua Caliente-Tucson_LAH_9066

In birds with zygodactyl feet, two toes (the first and fourth) point forward while the middle two point backward. This offers increased dexterity to species that use their feet to manipulate objects, such as parrots, and stabilizes birds that climb trees, such as woodpeckers. (But don’t forget yet another exception—the American Three-toed Woodpecker—with feet that are missing the first digit.) Then there are the trogons; where toes one and two are the backward ones, while three and four aim forward.

Some birds have built-in flexibility. Swifts can either turn all their toes forward—or not. This is a big help when you spend significant time hanging on a vertical wall. Owls, too, can choose which way their fourth digit points—helpful for birds that both perch in trees and grasp squirming prey. Notice how the Barn Owl on the left has three toes in front of the perch, while the one on the right has only two.

And speaking of perching… songbirds have thin feet and toes, ideally suited to hanging on to branches. I’ve long wondered how they keep their grasp even when asleep. It turns out that this feat is accomplished by a simple locking mechanism. The Achilles’ tendon runs down the back of the leg, enabling both birds and people to move their feet up and down. According to Ornithology.com,

When a bird lands on a branch, the ankle bends and the Achilles’ tendon is stretched. When the tendon stretches, it pulls on the toes and curls them around the branch. There is no muscular effort involved in holding onto the branch – it’s automatic. When the bird takes off, the legs straighten, the tendon relaxes, and the toes release their hold on the branch.

American Flamingos_WoodlandParkZoo-Seattle-WA_LAH_9763Then there’s the ago old question: why do flamingos (and some other birds) prefer to stand on one leg? A pair of neuromechanists—Lena Ting at Emory University and Young-Hui Chang at the Georgia Institute of Technology—recently came up with the surprising answer. It’s easier for the bird! Who would have guessed? Unlike with us humans, flamingos’ skeletons are arranged to perfectly center their weight over one side or the other. As when they’re holding onto a perch, no effort is required. Ting and Chang discovered that for a flamingo, standing on one leg is such a stable position, even dead birds can do it!


Birds, from top: Great Egret feet, Bush Stone-Curlew, Red-tailed Hawk, Osprey, Snowy Egret, Sandhill Crane, Cassowary, Greater White-fronted Geese, Mallard, Double-crested Cormorant, Comb-crested Jacana, Long-billed Curlew, American Coot, Australian King Parrot, American Three-toed Woodpecker, Barn Owl (2), and American Flamingo.

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