Raptor Hunting

One of the most spectacular sights in the world of birds is a kill of another bird by a stooping Peregrine Falcon. The falcon plunges steeply downward, wings partially closed, at speeds that can exceed 150 miles an hour. It was long thought that falcons and other raptors struck with their feet clenched like a fist. High-speed cinematographic studies, however, have shown that they strike their prey from above with all four toes fully extended. The Peregrine's victim is often ripped by the falcon's talons, producing a shower of feathers. Usually the prey is picked up off the ground afterward, although occasionally the falcon will stoop again and gather the tumbling bird before it falls to the ground.

Peregrines use other modes of hunting as well, sometimes diving past their prey and then zooming up from beneath to snatch it from behind and below, or simply catching a small bird from above with their talons. Sometimes they will patrol low over the ground like a harrier, attempting to flush game birds. The hunting success of Peregrines can vary widely with location, season, and even sex, as Cornell ornithologist Tom Cade showed with an interesting comparison. One breeding male in the eastern United States, hunting Blue jays almost exclusively, caught 93 percent of his targets one season. A breeding female in Australia was successful only 31 percent of the time, but she captured mostly coots which were more than five times as heavy as the Blue jays. Considering that the female probably weighed half again as much as the male, and analyzing the energy costs and benefits of both hunting patterns, Cade concluded that it took the male 49 kilocalories (kcal, what dieters normally just call a "calorie") to deliver 1,000 kcal of prey to the eyrie, while the female expended just 43 kcal to get the same job done. The female is more efficient, but is limited in the amount of time she can hunt because of her nest guarding duties. The somewhat less-efficient male probably delivered more nourishment to the young because he could spend more time hunting.

As a group, raptors exhibit an extraordinary variety of hunting techniques. Aside from owls (which are sometimes considered raptors) almost all are diurnal hunters, but a few like the European Hobby (a smaller relative of the Peregrine) will pounce on mice in the moonlight. Some are like the Peregrine in that they hunt at high speed. The Sharp-shinned Hawk, for example, often flashes through relatively thick woodland, maneuvering skillfully and often snatching passerines right from their perches. Others, like American Kestrels, Black-shouldered Kites, and the young of the very successful Red-tailed Hawk, often hover when hunting, and then drop steeply down on their targets. And still others, including adult Red-tails, soar as they watch for prey on the ground. But most hunting by raptors probably is done from perches with a commanding view from which the bird can scan the surrounding terrain with its telescope-like vision, where it can glide rapidly to gather in its prey. Interestingly, whether an American Kestrel hovers or perch-hunts depends in large part on whether there is a good breeze to hover in. Whichever technique is used, most prey of raptors are killed by the talons of the contracting foot being driven into their bodies; if required, the hooked bill is used to give a coup-de-grace. The exceptions are falcons, which ordinarily kill by biting into the necks of victims not dispatched in mid-air. (Owls also bite the necks of their prey.)

A Merlin stoops on an Inca Dove, killing it with a slashing blow of its open feet

Of course, there are some birds of prey (in addition to falcons) that employ rather specialized hunting techniques. Perched or hovering Ospreys plunge into water to grab living fish; Snail and Hook-billed Kites course around like harriers in pursuit of their less-than-agile preferred food: snails.

SEE: Hawk-Eyed; How Owls Hunt in the Dark; Size and Sex in Raptors.

Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.