Bird of the Month: American Kestrel
By Andy McCormick
PC: Mick Thompson (American Kestrel)
Scientific Name: Falco sparverius
Length 9 in
Wingspan 22 in
Weight 4.1 oz (117 g)
AOU Band code AMKE
If you see a small, long-winged bird hovering over an open field, most of the time it will be an American Kestrel. This type of hunting pattern is used by only a few species of birds and it is a trademark for a kestrel, which hovers by facing into the wind, flapping its wings and spreading its tail. It will glide to a new location and hover again to detect grasshoppers, other large insects and sometimes small rodents. The kestrel will also frequently be seen perched on a wire or exposed branch from where it will swoop down to catch prey.
The American Kestrel is sexually dichromatic. The male has grey-blue wings which contrast with its rufous back and a rufous tail with a black terminal band. The female has rufous wings barred with black. The tail is also rufous with black bands along its length (Smallwood & Bird). Both male and female have black moustachial stripes and a vertical black mark behind the eye giving them a striped-head look. The bill is small and the feet and legs are yellow.
There are nine North American falcons in the genus Falco, from the Latin falx, an agricultural implement with a curved blade, a scythe or sickle. The American Kestrel has the species name sparverius. In Early Modern English this was the term for Sparrow Hawk, which is still used as a common name for this bird. Kestrel is from the French, crecelle, a noisy bell, referring to its call, which is a high-pitched, loud and ringing killy-killy-killy-killy-killy (Holloway, Alderfer).
The American Kestrel is a cavity-nester using natural openings in trees (or cactus in the southwest), spaces between rocks, nooks in structures, and holes excavated by woodpeckers (Smallwood & Bird). Kestrels will readily use nest boxes when they are placed high in a tree. The birds do not build a nest but will make a scrape in whatever material is already in the cavity. Typically, 4-6 whitish, spotted eggs are deposited and then incubated by both parents for about a month. First flight occurs in another month with the parents continuing to feed the young kestrels for another 12 days.
Migration occurs in stages with northern breeding birds migrating first and others following in waves. It is thought that migration is stimulated by changes in available light. Kestrels can be seen in Washington year-round with some breeding in the state and others wintering from northern areas.
Two studies indicate that the life span for an American Kestrel may be between 1-2 years. However, average life span in captivity is five years. The North American population has changed in response to human intervention. Deforestation and farming increased kestrel habitat but forest regrowth, increased urbanization and sprawl has reduced open field acreage. Overall the American Kestrel has a stable population and remains our smallest, most widespread and well-loved falcon.