One of the things I love most about nature (aside from the sheer breathtaking beauty of it all) is its order. I love the way everything has a place, and each intricate piece fits together with all the other pieces in ways that are, for the most part, both irreducibly complex and logical. North America's falcons are a good example of this order. They remind me of a set of graduated mixing bowls or models of car, stepping right up the scale from the smallest to the largest option.
The largest of North American falcons (family Falconidae), and indeed the world's largest falcon, is the Gyrfalcon (
Falco rusticolus), an Arctic-breeding bird with a head-to-tail length of 22 inches and a wingspan of nearly four feet. In the mid-to-large size range are the Peregrine and Prairie Falcons (
F. peregrinus and
F. mexicanus, respectively), the Peregrine being just slightly larger than the Prairie on average. (Sort of like the difference between a Toyota Avalon and Camry.) Scaling down a little more is the Corolla-sized Merlin (
F. columbarius), a smaller bird measuring 11 inches long with a 24 inch wingspan. And at the bottom of the scale is the American Kestrel, the little Prius C, smallest of all North American falcons. (Forgive my lame comparisons - I'm not really a car person!)
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| American Kestrel (male) |
American Kestrels measure about 10 inches long, from head to tail, with a 22 inch wingspan. While their larger cousins, the Gyrfalcons, prey on birds and mammals as large as ptarmigans, gulls, hares and even young arctic foxes, the pint-sized American Kestrel targets equally pint-sized prey. Most often, their prey consists of invertebrates, such as grasshoppers, beetles, caterpillars, dragonflies and butterflies, but they will also take small mammals and birds when given the opportunity. (I think the bird in the photos above and below is munching on a Jerusalem cricket.)
All falcons are powerful, fierce, yet graceful hunters. Watching their aerial displays, pointed wings slicing through the air, is a real treat. Hunting in open country by day, American Kestrels often scan for prey from a perch atop a tree, fence post or utility wire. They also hover over fields and grasslands, beating their wings rapidly and "kiting," or hovering stationary in mid-air, before dropping down on their prey.
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| American Kestrel (male) |
Common and widespread across nearly all of North America, American Kestrels are a familiar sight in open country, like grassland and farmland, where they are often seen perched on fences and wires along roadways.
I mentioned how I admire the orderliness of nature, and here is another example: diurnal raptors often have an analogous nocturnal counterpart, mostly owls, which fit into similar ecological niches but operate at different times of day; the presence of one often indicates suitable habitat, nesting sites and prey, and therefore the presence of the other. For example, where you see Red-tailed Hawks during the day, you're likely to find Great-horned Owls at night (in fact, Great-horned Owls often nest in abandoned Red-tailed Hawk nests); marshy grassland habitat suitable for Northern Harriers is also fine for Short-eared Owls, where both species nest on the ground; forest-loving Red-shouldered Hawks may indicate the presence of forest-dwelling Barred Owls (generally in the eastern U.S.). And the presence of American Kestrels is often a sign that you are in Burrowing Owl habitat as well, since these small raptors favor similar dry, open county and target similar prey.
It may also be noted that both species are cavity nesters: the Burrowing Owl nests in abandoned ground squirrel burrows while the American Kestrel nests in cavities in trees or rocks that are either naturally occurring or were excavated by another creature, like a woodpecker. Kestrels also take readily to human-made nest boxes.
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| American Kestrel (male) |
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| American Kestrel (male) |
While the American Kestrel does not appear to be in any immediate danger, the North American Breeding Bird Survey indicates that populations have decreased by half since the 1960's. Ongoing threats to kestrels include clearing of standing dead trees, or snags, which they rely on for nest cavities, as well as extensive use of pesticides, which wipe out the insects, spiders and other invertebrate prey that make up the bulk of the kestrel's diet.
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| American Kestrel (female) outside of a nest cavity. |
Unlike most species of raptors, where it is nearly impossible to distinguish the male from the female (except by size, which is deceptive in the field), American Kestrels are sexually dimorphic; that is, the male and female exhibit different physical characteristics that allow them to be easily identified in the field. The slate-blue wings of the males are easily distinguished from the rust-and-black uniformly barred wings of the female; both male and female show the dark facial marks characteristic of most falcons.
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| American Kestrel (female) |
While American Kestrels are present in California's Great Central Valley year-round and in fact breed here, northerly populations in Alaska, Canada and some of the northern United States are migratory, and it seems that there are more kestrels in our area during the colder months, as local populations are augmented by overwintering birds.
While you're out exploring the wildlands this fall and winter (the best season for birding in the Valley!) be sure to keep an eye out for the diminutive American Kestrel, as well as its larger falcon cousins, all of which, except the Gyrfalcon, are common residents in and winter visitors to the Central Valley.
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