American Kestrel

Present and common in the county year round, but numbers increase somewhat during the winter. Prefers to hunt in open areas near woods or structures that provide perches. A common sight on power lines and other perches along rural roadways or kiting (motionless, wings spread, riding on air currents) or hovering (motionless, wings flapping) over fields, looking for its favored prey of small rodents and large insects. Also preys on small reptiles and small birds (“sparrow hawk” was once a common name for the Kestrel, the latin name sparverius means “related to sparrows”). Known to nest widely here, with many confirmed nesting sites in the southern part of the county. Mostly uses abandoned woodpecker holes, but may use other natural or artificial cavities. Highly territorial. Defends territory against even much larger birds. I have seen screaming kestrels chase birds as large as a Red-shouldered Hawk (Buteo linneatus). Less territorial, however, during migration when small aggregations of Kestrels may form without hostility. Sometimes referred to as the “wire falcon” for its habit of sitting on power lines.

Our smallest diurnal raptor, our smallest falcon. Male Kestrels are also our most colorful raptors. Males have a blue-grey cap and wings of the same color offset by rich rufous elsewhere on the upper parts, although the primaries are black or nearly black. Yellow eye-ring (often not clearly visible except at close range), yellow cere (the bump at the base of the bill), and yellow feet. The strong facial markings--notably two dark lines, one descending from below the eye, the other from well behind the eye and a dark spot at the back of the head--are distinctive. Note that at a distance these lines may blend into the rest of the face so that the white space between them becomes the most prominent facial feature, giving the bird a white-cheeked look. In flight, adult males from above are rufous on the back and tail (which has a dark terminal band) with blue-grey cap and wings (but black primaries). Note also a row of pale dots along the trailing edge of the wings (although these are hard to see in the field). Females from above look mostly rufous to brownish with the wingtips shading into darker tones. In flight from below, adult males are pale and mottled overall, but with a rufous wash on the breast and a markedly rufous tail. The dark terminal band on the tail is obvious from the ventral view as well. Females in flight from below are mostly pale-looking but finely barred with rufous with more rufous in the tail than elsewhere. Thin dark terminal band is much less obvious than in the male. Juveniles are similar to adults. The most common vocalization is usually described as a high-pitched killy-killy-killy, but to me it sounds more like klee!, klee!, klee!, klee!, klee! (klee! usually repeated about three to eight times).

Facial pattern and markings are suggestive of Peregrine Falcon (Falco peregrinus), but Kestrels are unlikely to be confused with that or any other bird except the much less common Merlin (Falco columbarius). Peregrine Falcon is a significantly larger bird (the largest female Peregrines being about 20 inches from head to tail, or about twice as big as a Kestrel, which is about the size of a Western Scrub-jay (Aphelocoma californicus)). In poor light, a Kestrel (particularly a female) can simply look dark, and its distinctive facial pattern can be hard to see in flight. Together these facts may make it hard to distinguish a Kestrel from a Merlin in some situations. However, Kestrel is a somewhat smaller, more delicately proportioned bird, typically with a lighter, more buoyant look in flight. Kestrels frequently hover or kite, Merlins rarely do--if ever. Kestrel has a proportionately longer tail. Merlins typically fly straight and fast. Although a Kestrel may do the same when hunting another bird, Kestrel tends to change direction fairly often for a more wandering flight pattern. When perched, Kestrels maintain their balance by occasionally raising and lowering their tails--which Merlin does not do (according to Dunne). Kestrels are generally skittish, leaving a perch when approached before a Merlin will. A flushed Kestrel usually (but by no means always) perches quickly again, however, without flying far away--which can make them exasperating to photographers trying to approach. Given a good view, however, plumage differences should be enough to distinguish the two birds.

Kestrel numbers appear to be declining in the San Francisco Bay Area. The reasons are obscure, but habitat destruction seems the most likely cause.

For current raptor migration information, visit the Golden Gate Raptor Observatory website