A few weeks ago I was researching some interesting facts for my post World of Woodpeckers. One of the featured facts was that woodpeckers have two forward and two backwards-facing toes, making their feet zygodactyl. I already knew about the toe directions, but was unfamiliar with the term zygodactyl, so i googled it.
That’s when a whole new world opened up for me: the world of bird feet. It’s not a topic that normally comes up in conversation, but bird feet are pretty amazing. There are different kinds of feet throughout the avian world. They serve a variety of functions and tell a lot about a bird’s ecology.
Functions of avian feet include perching, locomotion, preening, feeding, carrying/holding objects, scratching, reproduction (egg rolling, displays), and heat loss regulation.
Birds are animals that are considered digitigrade. This means that they generally walk on their toes, not on their entire foot like we do. Most birds have have 4 toes, or digits, although some only have 3. Bird digits can be arranged in a few different ways.
Anisodactyl feet are the most common digit arrangement in the bird world. This means that digit number 1 (which is similar to our big toe) faces backwards and the other 3 digits face forwards. This digit arrangement is found in passerines, or perching birds. Anisodactyl feet are extremely flexible because all four digits are independent. Therefore, digit 1 can be flexed to lock the toes around a perch. That’s why you don’t see birds falling out of trees when they sleep on a branch!
On zygodactyl feet, digits 1 and 4 face backwards while digits 2 and 3 face forward. This kind of foot in common in woodpeckers, most parrots, owls, and some other species. The shape of these feet help a bird climb up, down, and along the trunk of a tree. Parrots use their feet to hold food and bring it to their bill, in the same way that we use our hands to eat. Owls have zygodactyl feet to help them hold their prey and perch. Something unique about owls is that they can rotate their 4th digit forward.
There are 4 kinds of webbed feet, with the most common being Palmate.
- In palmate feet, digit 1 is backwards and digits 2,3, and 4 are connected by webbing. Examples include ducks, geese, gulls, terns, loons, and other aquatic birds.
- Semipalmate feet are found in sandpipers, plovers, herons, grouse, and avocets to name a few. These feet are similar to palmate but the webbing is smaller.
- Lobate feet have a backwards digit 1 and digits 2,3, and 4 have lobes of skin surrounding them. A few species with lobate feet include coots, grebes, and phalaropes.
- Totipalmate feet have all four digits connected by webbing. Some totipalmate birds are pelicans, cormorants, anhingas, boobies, frigatebirds, and gannets.
Raptorial feet are found in birds of prey (raptors). The toes of these feet are called talons. They are curved with sharp nails, strong, and large. These kind of feet make raptors lethal hunters.
Other (more uncommon) Feet
- Pamprodactyl feet have the 4 digits facing forward. However, the two outer digits (1 and 4) can be rotated backwards. This kind of foot is found in swifts.
- Another toe arrangement that is similar to zygodatcyl is heterodactyl. There are still 2 forward and 2 backwards, but instead digits 1 and 2 are backward and 3 and 4 are forward. This arrangement is only found in trogons.
- Syndactyl feet are found in Kingfishers. Digits 2 and 3 are fused together and digit 1 is very small and backwards.
- Didactyl feet are only found on ostriches. Didactyl means “two-toed”. The shape of this foot is similar to a horse’s hoof, so having along two toes aids in running and escaping predators.
- Tridactyl feet have only three digits, digit one is missing. Tridactyl birds include emus,.bustards, the Northern Three-toed Woodpecker, and quails.
The anatomy of birds is a broad and fascinating subject. There are over 10,000 birds species and so many variations/adaptations to learn about. I hope to present more bird anatomy posts in the future.
In the meantime, if you have any specific birds or topics you would like to know more about please let me know in the comment section.