For the Birds Radio Program: Bird Feet
Today, Laura puts a foot in her mouth–that is, a bird foot. Date sort of confirmed.
One of the things in the bird world that people take pretty much for granted is bird feet. Sure, we named a violet after them, but most people don’t actually pay much attention to the feet of birds. Hardly anyone even notices that the feet have been removed from chicken legs long before they reach the store, and most people don’t even know that domestic fowl have a sharp and nasty growth on their legs called a spur. This potentially lethal weapon helps roosters enforce their pecking order. In ancient Asia, where cock fighting originated, the natural spurs were made even more lethal by fitting them with iron spikes.
The Disney people, along with most cartoon artists, have obviously spent more time looking at parrot feet than at other kinds of bird feet. They draw all birds, no matter what species, with two fleshy toes in front and two behind, just right for climbing tropical trees or stomping out Sylvester the Cat. When real birds have their toes arranged with two toes in front and two behind, ornithologists say they’re zygodactylous. Woodpeckers have zygodactyl feet, too, but their toes are slender and hard, covered with the same material as our fingernails, and have unusually long, curved claws, the better to cling to trees with.
The powerful, muscular toes of hawks and owls are called talons. Osprey, which are specialized fish eaters, have specialized talons. Under each toe, the Osprey has pads with sharp spicules which help it to grasp wet, slippery feet.
Everyone knows that ducks have webbed feet, but not many people spend their time contemplating the feet of gulls. I often hear grownups exclaim with surprise when they first notice webbed feet on Ring-billed Gulls as they feed them french fries at fast food joints. Loons also have webbed feet, but they are obviously much harder to observe in the wild. The webs on all these birds run between the three front toes. Pelicans and cormorants have webs between all four toes, giving their feet the fancy name totipalmate.
Swifts don’t need their feet for much—they spend most of their lives on the wing. Their feet are so little that their family is officially called Apodidae, which literally means “without feet.” Their feet may be tiny, but they are also uniquely specialized, having all four tiny toes facing forward. Each toe is armed with a powerful and curved claw. They may not be able to walk around or even perch, but their special feet enable swifts to cling to the insides of chimneys and hollowed-out tree snags.
Herons and egrets have a long back toe which enables them to perch in trees. People are often surprised to learn that these huge birds even nest in trees. Cranes are sometimes mistaken for herons, but their tiny back toe, placed high on the tarsus, makes it impossible for cranes to perch. They spend their lives on the ground or in the air, never in between.
Many bird feet have wonderful adaptations for coping with the difficulties presented by snow and ice. Ruffed Grouse toes grow comblike fringes for winter, which may help a little in supporting the grouse’s weight on snow, like snowshoes, but also help the grouse from slipping on icy branches. The Wilow Ptarmigan’s feet have even finer snowshoes, made both by feathers that grow on the toes and claws that double in size to support the bird’s weight even in the softest snow. The soles of the feet of ravens are coated with keratin, which is a poor heat conductor. This coating is six times thicker in the Arctic raven than in subtropical ravens.
All in all, when you’re studying birds, read the field guides but don’t forget to check out the foot notes, too.