September 13, 2011

American Kestrel and a legacy

From the Massachusetts Breeding Bird Atlas 1
Atlas 1 data collected from 1975-1979

American Kestrel
Falco sparverius
Egg Dates: April 19 to July 5
Number of broods: one; may re-lay if first attempt fails.

The American Kestrel belongs to a group of small falcons with a worldwide distribution. Our British forefathers mistakenly named it “Sparrow Hawk” after Europe’s small accipiter of the same name. In North America, the species nests from the Arctic tree line south across much of Canada and the United States, where it is the commonest falcon. During the Atlas period, kestrels were “confirmed” breeding in all sections of the state. Populations were densest in eastern Massachusetts, including Cape Cod and the Islands, and were sparsest in portions of the hill country in central regions.
The adult male, which has blue wings, two sharp, vertical, black stripes contrasting against a light face, and a bright rufous tail, is certainly the most colorful of North American hawks. The somewhat larger female is not as brilliant as the male and has its upperparts entirely rufous, and barred with black. Kestrels tend to perch high and conspicuously in the open, making them easily visible. They can be tamed readily and will reproduce in confinement. Many falconers have noted that the small males are more docile and tractable than the females.

Spring migration occurs mainly during March and April, and by the latter month local breeders are on their territories at woodland borders, fields, pastures, and the edges of highways. As the breeding season approaches, kestrels abandon their solitary winter habits. Members of a pair often perch side by side, and courtship consists of aerial displays by the male above a perched or flying female. The male ascends on rapidly fluttering wings and then plunges steeply, giving the familiar, repetitive killy-killy or kee-kee call, which is used not only in courtship but also at other times of excitement. Copulation during this period is frequent and precedes egg laying by several weeks.

Preferring a covered nest site, kestrels choose a hole in a tree, post, or roof. Cavities excavated by flickers may be used, and the birds will readily occupy nest boxes. Because the latter are the most accessible to observe, most Atlas information on nesting comes from pairs using these artificial sites. In one sample of Massachusetts nests, 23 were in boxes and 1 was in a cavity in a maple (CNR). Clutches of three to five (rarely six or seven) eggs are laid. Incubation, mostly by the female, lasts 29 to 30 days. If the first clutch is lost, she often lays a new set of eggs. In Massachusetts, 17 records of nestlings range from May 19 to August 4 (CNR), and brood sizes in 125 nests were as follows: one (6 nests), two (15 nests), three (32 nests), four (30 nests), five (41 nests), and six (1 nest) (Olmstead). The juveniles are ready to fly about 30 days after hatching. The family stays together for some time after fledging, even when the young are feeding on their own.

Kestrels vary their hunting and feeding habits depending on the prey available. Ordinarily, they perch high, dropping down after spotting an insect or small mammal and then returning to the same spot, pumping or bobbing the tail upon alighting. At other times, they make forays into the open, heading into the wind with the body tilted diagonally upward and hovering with the tail fanned out. They also pursue small birds, plucking an unsuspecting individual from a perch or capturing it in midair.

By late August and early September, kestrels begin to depart for the southern states and beyond, with northern migrants passing in September and October. Some of these northern birds winter here, and a few of the breeders may be permanent residents. Kestrels are encountered in winter throughout the state but are more common in coastal sections.

Note: fairly common and widespread in grasslands and smiliar open situations; possibly declining

Nancy A. Claflin

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