Colorful American kestrel is deadly to prey Albany

[Donna]

The days are getting shorter; up in the hills you will occasionally find a telltale red leaf; the goldenrods and asters are coming into their full glory; and soon beechnuts and acorns will start falling from the trees. The signs are plentiful that autumn is just around the corner.

One sign that I particularly enjoy is the appearance of American kestrels on the telephone wires that hang next to open fields. The American kestrel is the smallest and most colorful falcon in North America.

Worldwide, there are 58 species of falcons. 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 species: the gyrfalcon, the peregrine falcon, the Merlin and the American kestrel. The American kestrel's European cousin is simply known as the kestrel.

The prototypical falcon is a medium-sized predator that relies on speed to hunt other birds in open country. Falcons are designed for speed: The peregrine falcon, the fastest bird on Earth, has been clocked at up to 275 mph. Long, slim tails and long, swept-back wings help falcons to overtake most birds in a flat-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 (Falco sparverius) measures in at a diminutive 9-12 inches. Gyrfalcons are large enough to hunt and kill geese and can also prey on anything smaller. American kestrels are somewhat limited in their choice of prey animals, being able only to tackle sparrow-sized birds.

This explains a 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 sparrow hawk stuck. Even the American kestrel's scientific name (Falco sparverius) is inappropriate. ''Falco" is fine, 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 will utilize mice, voles and even grasshoppers for food. By taking advantage of such food items, American kestrels were 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 in order to get a clear view of mice and grasshoppers from up in the air an American kestrel must stay still.

So, American kestrels developed broad, fan-shaped tails that they spread out and use as air brakes to assist them in hovering. Kestrels hover with rapid wingbeats (much like hummingbirds), but once they spot a prey animal they can fold up their tails and dive to earth 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 the fact 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 fields.

A drawback of their small 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, such as blue jays and crows, from attacking, because the larger birds can never be sure where the kestrel is looking.

There is no real nest-building that needs to be done, so the female just lays her 3-7 eggs on the floor of the cavity. While one adult incubates the eggs, the other will be out defending the territory and looking for food. As soon as the babies hatch and are about 1 week old, both adults will be out trying to keep them all fed.

American kestrels are more noticeable at this point of the year than at any other as they gear up for their fall migration and can be seen sitting on telephone lines that border large fields. Be particularly sure to look for them near dairy farms, where they seek out small birds and mice.

[MAK]