The American kestrel is the smallest falcon in North America. There are 58 species of falcons and they can be found on every continent except Antarctica. Here in North America, we have a total of seven falcons, but in the eastern U.S. we are only likely to see four of them: the gyrfalcon, peregrine falcon, the Merlin, and the American kestrel.
The prototypical falcon is a medium-sized predator that hunts other birds in open country. As a result, falcons are designed for speed, with the peregrine being the fastest bird on Earth (clocked at 275 mph!). Long, slim tails and long, swept-back wings help falcons overtake most other birds in a fl at-out race. As with everything in nature, however, there are exceptions.
The gyrfalcon (Falco rusticolus) is the largest, measuring 25 inches from head to tail, while the American kestrel (F. sparverius) measures in at a diminutive 9 to 12 inches. Gyrfalcons are large enough to kill geese, but American kestrels are somewhat limited in their choice of prey animals and are only able to tackle sparrow-sized birds.
This explains the popular folk name “sparrow hawk.” Sparrows represent only a small portion of the American kestrel’s diet, and American kestrels are falcons not hawks, but the name stuck. Even the American kestrel’s scientific name (Falco sparverius) is inappropriate. “Falco” is fi ne, but “sparverius” is nothing more than the Latinized form of the French word “espervier,” which means “sparrow hawk.”
Because of their small size, American kestrels are able to utilize mice, voles, and even grasshoppers for food. By taking advantage of such food items they are able to stay in traditional falcon habitat (open country) while avoiding competition with larger species. This kind of behavioral adaptation did require an accompanying physical adaptation, however.
Hunting grasshoppers and mice requires a technique quite different from the standard falcon approach. American kestrels have very good eyesight, which allows them to identify prey animals from great heights.
But to get a clear view of mice and grasshoppers from up in the air, they must stay still. So they developed broad, fan-shaped tails that they can spread out and use as air brakes to assist in hovering.
Kestrels hover with rapid wing beats, but once they spot a prey animal they can fold up their tails and dive with great speed. As a result of their lifestyles, American kestrels have much longer and broader tails than most other falcons.
Another advantage of their small size is that they can nest in natural cavities in trees. They also use old woodpecker holes and will readily utilize nest boxes that are put up in trees at the edges of fi elds.
A drawback of their size is vulnerability to attacks from larger birds. To protect themselves, American kestrels developed false eye spots on the backs of their heads. This may deter larger birds from attacking them because the larger birds can never be sure where the kestrels are actually looking.
SEEKING THEM OUT
It may seem odd to contemplate a trip for the purpose of falcon watching, but that should not deter you from actually trying it. American kestrels can be found anywhere there are large, open fields and with just a little effort you should be able to spot one fairly easily.
A great place to start looking is on the telephone wires that might run parallel to the edge of a field. Kestrels are about the same size as a mourning dove. With a little practice, you’ll quickly be able to tell the two birds apart.
Bill Danielson is a professional nature photographer and author living in Altamont. Contact him at www. speakingofnature.com.