About the size of a Mourning Dove, the American Kestrel is North America’s smallest, most common, and most widespread falcon. The colorful male wears rufous above, with gunmetal blue wings and a pale and lightly spotted chest and belly. The less colorful but still lovely female shows barred rufous brown above and is similarly pale and lightly spotted below. The pale faces of both sexes have 2 very distinctive vertical slashes—a field mark that can often be easy to spot even on a bird perched on a power line as you drive by at 55 m.p.h. And indeed, rural utility lines are great spots to check for these little hunters, as they scan the ground below for prey. But they can hover mid-air, if suitable perches are lacking and the breeze is just right. A hovering bird faces into the wind, while the wings alternately flap and glide and the tail constantly adjusts to each change in the breeze.
Kestrels typically inhabit open areas covered by short ground vegetation where they hunt primarily from perches. Their diet consists primarily of large insects, with grasshoppers high on the menu, along with beetles, dragonflies, moths, and caterpillars. They’ll also eat small mammals (e.g., voles, mice) and occasionally a small bird. They capture most prey on ground, although some individuals can become adept at capturing flying insects or small birds on the wing.
Spring migration stretches from late March to early May in Colorado. Kestrels breed throughout most of the state except in the highest mountains and the agricultural areas of the Eastern plains. Returning males arrive on the breeding grounds about a week earlier than the females, who follow about a week later. They nest in existing tree cavities when available and may evict woodpeckers, starlings, flickers, chipmunks, and squirrels, although sometimes those dastardly starlings prevail. The species also readily takes to human-constructed nest boxes. The female lays 4 – 5 eggs, incubating them for 29 – 31 days. The male may take a turn or two at incubating, although the female bears the greater burden of this task. Mom remains with the nestlings most of the time at first, while Dad brings food for the entire family. But after a couple of weeks, she also joins in on the hunting tasks. The youngsters take their first flights out of the nest about 28 – 31 days after hatching. By the time they fledge, the youngsters have plumage very similar to their adult coloring, so it’s easy to tell the sex of the young. Just check the color of the wings—blue, male; rufous, female. Parents continue to feed the fledglings for 10 – 12 days. Although a few kestrels stick around through the winter, most in our area migrate beginning in early August through early December, with peak movement in September and October.
As the only kestrel in North America, The American Kestrel’s common name (“American) differentiates this species from the 13 other kestrel species in the world. “Kestrel” derives from the French crecelle—a noisy bell, allegedly referring to this bird’s call. Its scientific (Falco sparverius) arises from falx (Latin), an agricultural implement with a curved blade (referring to its hooked talons), and sparve (Modern Early English), a colloquial form of sparrow in England. Indeed, North American kestrels used to be called “sparrow hawks”—a misnomer in 2 ways. First, they’re not hawks but falcons; second, sparrows and other small birds make up probably less than 5% of their diets.
American Kestrels often hang around human-modified habitats, such as pastures and parks. As a result, you can often see them near areas of human activity, including some heavily developed urban areas. So as you drive around this summer, keep an eye out for this little hunter, peering intently at the ground from a utility wire. Once you start looking, you may be surprised to see them around!
You can learn more about this little falcon here.