American Kestrel

American Kestrel (Falco sparverius)

The American Kestrel sometimes known as the Sparrow Hawk, is a the smallest falcon and the only kestrel found in the Americas. It is the most common falcon in North America, and is found in a wide variety of habitats.

Its breeding range extends from central and western Alaska across northern Canada to Nova Scotia, and south throughout North America, into central Mexico and the Caribbean. It is a local breeder in Central America and is widely distributed throughout South America. Most birds breeding in Canada and the northern United States migrate south in the winter.

The American Kestrel is sexually dimorphic, although there is some overlap in plumage coloration between the sexes. the sexes differ more in plumage than in size. Males have blue-greywings with black spots and white undersides with black barring. The back is rufous, with barring on the lower half. The belly and flanks are white with black spotting. The tail is also rufous, with a white or rufous tip and a black subterminal band.

The back and wings of the female American Kestrel are rufous with dark brown barring. The undersides of the females are creamy to buff with heavy brown streaking. The tail is noticeably different from the male’s, being rufous in color with numerous narrow dark black bars.

Juveniles exhibit coloration patterns similar to the adults’. In both sexes, the head is white with a bluish-grey top. There are also two narrow, vertical black facial markings on each side of the head, while other falcons have one. Two black spots (ocelli) can be found on each side of the white or orangish nape. The function of these spots is debated, but the most commonly accepted theory is that they act as “false eyes”, and help to protect the bird from potential attackers. The wings are moderately long, fairly narrow, and taper to a point.

The bird ranges from 12 to 27 cm (4.7 to 11 in) in length with a wingspan of 50–61 cm (20–24 in). The female kestrel is larger than the male. The male weighs 80–105 g (2.8–3.7 oz), as opposed to the female which weighs 100–120 g (3.5–4.2 oz). In standard measurements, the wing bone is 16–21 cm (6.3–8.3 in) long, the tail is 11–15 cm (4.3–5.9 in) and the tarsus is 3.2–4 cm (1.3–1.6 in).

American Kestrels feed largely on small animals such as grasshoppers, dragonflies, lizards, mice, and voles. They will occasionally eat small birds. The kestrel has also been reported to have killed snakes, bats, and squirrels.

The kestrel is able to maintain high population densities, at least in part because of the broad scope of its diet. The American Kestrel’s primary mode of hunting is by perching and waiting for prey to come near. The bird is characteristically seen along roadsides or fields perched on objects such as trees, overhead power lines or fence posts. It also hunts by kiting, hovering in the air with rapid wing beats and scanning the ground for prey. Other hunting techniques include low flight over fields, or chasing insects in the air.

American Kestrels do not use nesting materials. If the cavity floor is composed of loose material, the female hollows out a shallow depression there. American Kestrels nest in cavities, although they lack the ability to excavate their own. They rely on old woodpecker holes, natural tree hollows, rock crevices, and nooks in buildings and other human-built structures. The male searches for possible nest cavities. When he’s found suitable candidates, he shows them to the female, who makes the final choice. Typically, nest sites are in trees along wood edges or in the middle of open ground. American Kestrels take readily to nest boxes.

References: Wikipedia, Cornell Lab of Ornithology