The American kestrel is the smallest and most common falcon in North America. In contrast to many other raptors, the males and the females in this species differ more in plumage than in size. Males have blue-grey wings with black spots and white undersides with black barring. Their 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. Their tail is rufous in color with numerous narrow dark black bars.
Read Pritish Kumar Halder article, in which he discusses about American Kestrel
The breeding range of American kestrels extends from central and western Alaska across northern Canada to Nova Scotia, and south throughout North America, into central Mexico and the Caribbean. They are local breeders in Central America and are widely distributed throughout South America. Most birds breeding in Canada and the northern United States migrate south in the winter, sometimes going as far as Central America and the Caribbean.
American kestrels are found in a wide variety of habitats, including grasslands, meadows, deserts, and other open to semiopen regions. They can also be found in both urban and suburban areas. Their habitat must include perches, open space for hunting, and cavities for nesting.
Under traditional classification, the American kestrel is the smallest raptor in America. The American kestrel is sexually dimorphic, although there is some overlap in plumage coloration between the sexes. The bird ranges from 22 to 31 cm (8.7 to 12.2 in) in length with a wingspan of 51–61 cm (20–24 in). The female kestrel is larger than the male, though less so than larger falcons, being typically about 10% to 15% larger within a subspecies.
The more northern subspecies tend to larger sizes, with a large northern female being about twice the size of a small southern male. The male typically weighs 80–143 g (2.8–5.0 oz), and the female 86–165 g (3.0–5.8 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).
Physically, American kestrels are leaner and less muscular than larger falcons. The pectoral flight muscles of the American kestrel make up only about 12% of its body weight, as compared to about 20% for the strongest flying falcons such as the peregrine. The wings are moderately long, fairly narrow, and taper to a point.
Their less muscular body type is adapted to energy-conserving ambush hunting, rather than spending large amounts of energy-consuming time on the wing and getting into long tail-chases of bird prey. For their size, they have strong talons and beaks, and can swiftly dispatch prey. Their lean build and energy-conserving strategy allow a lower daily food intake than if they were more strongly muscled, yet with enough strength to commonly take bird prey as large as themselves, and occasionally larger.
Habits and Lifestyle
Outside of the breeding season, American kestrels spend their time singly. They usually hunt by day in energy-conserving fashion; they perch and scan the ground for prey to ambush or may also hunt from the air. They are often seen along roadsides or fields perched on objects such as trees, overhead power lines, or fence posts.
They also hunt by kiting, hovering in the air with rapid wing beats and scanning the ground for prey. Other hunting techniques include a low flight over fields or chasing insects and birds in the air. Prey is most often caught on the ground, though occasionally they take birds in flight. Before striking, the kestrel characteristically bobs its head and tail, then makes a direct flight toward the prey to grab it in its talons.
American kestrels communicate with thelp of three basic vocalizations – the “klee” or “killy”, the “whine”, and the “chitter”. The “klee” is usually delivered as a rapid series – klee, klee, klee, klee when the kestrel is upset or excited. This call is used in a wide variety of situations and is heard from both sexes. The “whine” call is primarily associated with feeding. The “chitter” is used in courtship feeding, mating, and feeding of nestlings.
Diet and Nutrition
American kestrels are carnivores and feed largely on small animals such as grasshoppers, dragonflies, lizards, mice, voles, and small birds. They may also hunt snakes, bats, and squirrels.
American kestrels are monogamous and form strong long-lasting pair bonds. In migratory populations, the males arrive at the breeding ground before females, then the female selects a mate. Males perform elaborate dive displays to advertise their territory and attract a mate. These displays consist of several climbs and dives, with three or four “klee” calls at their peaks. Pairs usually use previous nesting sites in consecutive years.
American kestrels are cavity nesters, but they are able to adapt to a wide variety of nesting situations. They generally prefer natural cavities (such as in trees) but will also nest in holes created by large woodpeckers, or use the abandoned nests of other birds. They may even nest on cliff ledges and building tops, or utilize nesting boxes. The female lays 3 to 7 eggs which are white to cream in color with brown or grey splotching.
Incubation usually lasts 30 days and is mainly done by the female. Hatchlings are altricial (helpless) and are only able to sit up after 5 days. They grow very quickly, reaching an adult weight after 16-17 days. After 28-31 days, they are able to leave the nest and depend on their parents another 2 or 3 weeks. American kestrels usually reach reproductive maturity and may breed from a year old.
The main threat to American kestrels is habitat loss as a result of longleaf pines being cleared from agricultural fields. They also suffer from competition with other birds for nest sites, from hunting and trapping, road collisions and predation by other raptors.
According to the All About Birds resource the total population size of the American kestrel is around 9.2 million individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
Fun Facts for Kids
- American kestrels have two black spots (ocelli) on each side of their 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 kestrels from potential attackers.
- The American kestrel is also known as grasshopper hawk, due to its diet, and killy hawk, due to its distinct call.
- There are 17 subspecies of the American kestrel and each varies in color, size, and vocalizations.
- The American kestrel is commonly used in falconry, especially by beginners. Though not as strong a flyer as many other, larger falcons, proper training and weight control by the falconer allows many American kestrels to become effective hunters of birds such as sparrows and starlings.