One of the more common fall migrant raptors in eastern North America is the American Kestrel (Falco sparverius). This brightly-colored small falcon is now almost gone from Westchester and Putnam counties as a breeder, but continues to migrate through our area in good numbers. It is often seen hovering above open fields as it hunts. Its European counterpart, the Eurasian Kestrel (Falco tinnunculus), is called the “windhover” in parts of Britain because of this habit.
The Kestrel is our smallest diurnal raptor, roughly the size of a Blue Jay. The intricately patterned plumage of male and female kestrels is markedly different. Female kestrels average slightly larger than males. The back, tail, and upper surfaces of the wings are rufous with thin horizontal black barring. The underparts are white, with vertical, smudgy rufous streaking on the breast and belly. The head has a dark gray cap, with two vertical gray stripes pointing down from the cap onto the side of the head, and a single gray spot on the nape, all against a white background.
The male shares the female’s barred rufous pattern on his back, but his wings are slate-gray, and the tail is all rufous, except for a thick black band at the very end of the tail, and the outermost tail feathers are white. The male’s underparts are a very light tan, broken up by scattered gray spotting, except for the undertail coverts, which are pure white. The male’s head pattern has the same two vertical stripes and single spot, but they are a darker gray, almost black, and his gray cap is adorned with a single rufous spot on the very top of the head.
Kestrels are largely insectivorous in the warmer months, and the peak of their migration in September seems to be timed to coincide with the peak of dragonfly migration, providing these birds with an abundant source of food as they make their way south to the southern United States and Mexico to spend the winter.
Kestrels prefer large open fields with dead trees or other suitable sources of cavities for nesting. Like almost all grassland-inhabiting birds in the northeast, kestrels have declined due to reforestation and the loss of open fields to development. Protect these habitats. The cutting of dead trees and competition for scarce nest sites with starlings also pose problems. If you put up a kestrel box, be sure to monitor it for starlings.