The American kestrel (Falco sparverius), also called the sparrow hawk, is the smallest and most common falcon in North America. It has a roughly two-to-one range in size over subspecies and sex, varying in size from about the weight of a blue jay to a mourning dove. It also ranges to South America and is a well-established species that has evolved into 17 subspecies adapted to different environments and habitats throughout the Americas.
Description: 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 (northern hemisphere), 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).
Vocalizations: The American kestrel has 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, but the larger females typically have lower-pitched voices than the males. The “whine” call is primarily associated with feeding but is also uttered during copulation.
Ecology and behavior: American kestrels are found in a wide variety of habitats, including grasslands, meadows, deserts and other open to semi-open regions. They can also be found in both urban and suburban areas. A kestrel’s habitat must include perches, open space for hunting, and cavities for nesting .
The American kestrel is able to live in very diverse conditions, ranging from above the Arctic Circle to the tropics of Central America, to elevations of over 4,500 m (14,800 ft) in the Andes Mountains.The bird is distributed from northern Canada and Alaska to the southernmost tip of South America, Tierra del Fuego. It is the only kestrel found in the Americas,though as mentioned above this classification is genetically inaccurate. It has occurred as a vagrant in the UK, Denmark, Malta and the Azores.
Feeding: American kestrels feed largely on small animals such as grasshoppers,crickets, butterflies, moths,[35] dragonflies, beetles,lizards, mice, voles, shrews, frogs,and small birds. The kestrel has also been reported to have killed scorpions, 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 and birds in the air.
Status and conservation: The American kestrel is likely the most abundant falcon in North America, although its total population is difficult to quantify, as local populations can change quickly due to resource availability. Count data from the USGS Breeding Bird Survey (BBS) indicate that the North American breeding population is experiencing long-term and gradual but sustained declines, with some regions, such as New England and coastal California, exhibiting more rapid declines.
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