American kestrel

Name and taxonomy

Carl Linnaeus named the species in 1758, in the tenth edition of Systema Naturae. He worked from an account of a little hawk that Mark Catesby published in the 1730s. Catesby collected in Carolina, so the type locality is now fixed there. The genus name Falco comes from a late Latin word for a falcon. The species name sparverius is medieval Latin and means a sparrowhawk. The English word kestrel arrived through the French crecerelle, a word for a ratchet rattle.

North American books called this bird the sparrow hawk for most of two centuries. The American Ornithologists' Union dropped that name in 1983, because it pointed at the wrong family. The Eurasian sparrowhawk belongs to the genus Accipiter and is only a distant relative. Older names include grasshopper hawk, which describes the food, and killy hawk, which copies the call. Seventeen subspecies are recognised, and they differ in size, voice and plumage.

Evolution and relatives

The kestrel belongs to the family Falconidae, which holds the falcons, the caracaras and the forest falcons. Falcons are not close kin of hawks and eagles, and they sit near the parrots and the songbirds. For many years this bird was grouped with the kestrels of Europe and Africa. DNA work moved it away from them, and it now sits at the base of the other falcons. The resemblance is probably a case of convergent evolution, because both groups hunt small ground animals. Nobody has renamed the bird, so it keeps a name that its genes do not support.

Species in the genus Falco stay close enough that most pairs can be crossed by artificial insemination. The spot-winged falconet of South America is almost as small as this kestrel. The 17 subspecies run from large northern birds to small tropical ones. That range in size is wide, and northern birds tend to be the larger ones.

Appearance

This is a slim falcon with long pointed wings and a long tail. The body runs from 22 to 31 centimetres, and the wings span 51 to 61 cm. A male weighs 80 to 143 grams and a female 86 to 165 g. The female is the larger sex, usually by 10 to 15% within one subspecies. The bill is short and hooked, and it measures about 1.2 to 1.4 centimetres. The tail is 11 to 15 cm long, and the wing bone is 16 to 21 cm.

The two sexes differ more in colour than in size, which is unusual among raptors. A male has blue-grey upper wings with black spots, and a rufous back barred at the rear. His tail is rufous, with a black band near the pale tip. A female has rufous wings and back, both barred with dark brown. Her underparts are cream to buff with heavy brown streaks, and her tail carries many narrow bars. Both sexes wear a white face crossed by two black stripes, under a blue-grey crown.

Two black spots sit on the pale nape, and they may work as false eyes. A young bird looks much like an adult female. The flight muscles make up about 12% of the body weight. In a peregrine falcon the same muscles reach about 20%, which shows how lean a kestrel is.

Habitat and range

A kestrel needs three things: open ground to hunt over, a perch, and a hole for its eggs. Where it finds them it settles, from prairie and pasture to desert, town park and roadside. The species breeds from central Alaska and northern Canada south to Tierra del Fuego. It lives above the Arctic Circle in summer and at over 4,500 metres in the Andes. GBIF holds occurrence records from 72 countries.

Birds that breed in Canada and the northern United States move south for the winter. Those that breed below about 35 degrees north usually stay in place all year. Some northern birds reach Mexico, Central America and the Caribbean. In winter the sexes separate, and females hold the most open ground. One reading of that pattern is that the larger females arrive first and drive males away. Stray birds have reached the United Kingdom, Denmark, Malta and the Azores.

Diet and hunting

The American kestrel eats whatever small animal is common near its perch. Grasshoppers, crickets, beetles, dragonflies, moths and butterflies fill the summer diet. In winter it turns to mice, voles, shrews, lizards, frogs and small birds. One study in a town found insects at 78% of the food and mammals at 14%. Reptiles and amphibians made up 6% of that diet, and birds 3%. Kestrels have also killed scorpions, snakes, bats and squirrels.

The usual method is to sit on a wire or a bare branch and study the ground. The bird bobs its head and tail, then flies straight down and grips the prey in its feet. It also hovers on fast wing beats, holding one point in the air while it looks below. Other hunts are low flights across a field, or a chase after an insect on the wing. A kestrel often carries a catch to a high perch, away from animals on the ground. The broad diet is probably the main reason the species is so widespread.

Behaviour and social life

The American kestrel lives alone for most of the year. It pairs in the breeding season and defends a territory around the nest hole. Quarrels over prey, perches and holes involve circling, diving and loud calling. One bird gives way in the end, and the loser leaves the ground it fought for. Home ranges are small for a raptor, at about 4.5 to 5.2 square kilometres.

The flight is quick, with rapid beats broken by short glides. Kestrels bathe in shallow water and during rain showers. They also take dust baths, throwing dust through the feathers with the wings. The dust probably cuts the number of feather mites and other parasites. After the young leave the hole, a family may hunt together for a short time. Hunting is a daytime job, and the bird roosts at night.

Communication and senses

The kestrel uses three main calls. The klee, often written killy, is a fast repeated note given in alarm or excitement. Both sexes use it, and females call at a lower pitch than males. The whine goes with food, at a meal and during mating. The chitter passes between a male and a female at courtship, mating and the feeding of chicks. Nestlings give calls like an adult's at about 16 days old.

Sight is the sense that matters most to a hunting kestrel. A perched bird appears to pick an insect out of grass long before a person would. Keen eyesight is also the main defence against a predator. Display flights carry information as well, and a male climbs and dives while calling. Birds signal to each other with posture and with the pattern of the plumage.

Reproduction and life cycle

American kestrels can breed in their first spring. In migratory populations the male arrives first, and the female then chooses a mate. He climbs and dives over the territory, calling at the top of each climb. Pairs form a strong bond, and many stay together for life. A pair usually returns to the same hole in later years, which gives it local knowledge. The male passes food to the female for weeks before she lays.

The species builds nothing and takes a ready-made cavity. Tree holes, old woodpecker holes, cliff ledges, cactus cavities and gaps in buildings all serve. Kestrels use wooden boxes readily, and box schemes now support many pairs. A clutch holds three to seven eggs, and four or five is the usual number. Each egg is white or cream, blotched with brown and grey. An egg measures about 32 by 29 millimetres, which is large for a bird of this size.

Incubation lasts about 30 days, and the female does most of it. The male sits for 15 to 20% of the time. Chicks hatch blind and helpless, over three or four days. They reach an adult weight in about 16 to 17 days. The young leave the hole 28 to 31 days after hatching. They still depend on their parents for about three more weeks.

A pair raises one brood a year, and tries again if the first fails. Lost eggs are usually replaced within 11 to 12 days. Most wild kestrels live 3 to 5 years. The oldest ringed wild bird reached 11 years and 7 months. Captive birds have lived up to 17 years.

Predators and threats

Larger raptors take kestrels, above all the great horned owl, the red-tailed hawk and the prairie falcon. Cooper's hawk is bold enough to attack a kestrel that is busy on the ground. Raccoons, skunks, bobcats, coyotes and snakes rob the nest holes. Most losses fall on eggs, chicks and birds in their first year. In Florida, large introduced snakes such as Burmese pythons have eaten kestrels.

People cause far more deaths than predators do. One review of 1,355 reported deaths blamed humans for 43.2% and predation for 2.8%. Those figures are biased, because a dead bird is easier to find near a road or a house. Pesticides reach kestrels through the animals they eat. Flame retardants called PBDEs weaken the immune system and disturb the thyroid gland. PCBs change plumage colour, delay laying and lower breeding success.

Population and conservation

The IUCN lists the American kestrel as Least Concern. Its 2025 assessment put the world population at about 9.2 million mature birds. An older estimate gave 1.2 million pairs in North America, with as many again to the south. A smaller count put about 236,000 birds in North America in winter. Numbers probably rose in the 18th and 19th centuries, as forest gave way to farmland.

Since 1966 the North American breeding population has fallen steadily. Counts at migration watch sites agree with the breeding bird survey. New England and coastal California have lost birds faster than the rest. The southeastern subspecies Falco sparverius paulus has declined by 82% since 1940. Clearance of longleaf pine for crops took away the holes it needed. Fewer holes, fewer insects, more pesticide and competition from starlings are all suspected.

The Peregrine Fund started the American Kestrel Partnership in 2012. It runs a web network where volunteers and scientists enter nest box records. Researchers use the data to link nesting success to land use, weather and pollution. A camera streams from a box at the fund's campus in Boise, Idaho, each season.

Relationship with humans

This is the classic beginner's bird in North American falconry. Its small size makes it easy to keep, but its weight must be managed with care. Trained birds hunt sparrows and starlings, and bold ones tackle prey twice their own weight. Falconers call the small-scale sport micro-hawking, and it needs no dogs and no wide estate. A wild-caught bird often feeds from the hand the day after capture. In the United States, Canada and Mexico a permit is needed to hold one.

Farmers value kestrels because they take grasshoppers, mice and voles from the fields. Boxes on farm buildings and fence posts bring pairs onto working land. Public health officers watch sick and dead kestrels as an early sign of West Nile virus. Researchers use the species widely, because it breeds well in captivity. A kestrel now and then kills a chicken chick or a very small pet.

In culture and myth

Many local names for this bird appear to copy the sound of its call. Brazilian Portuguese speakers call it quiriquiri, and some Spanish speakers call it cliclí. Birdwatchers in the United States write the common call as killy-killy-killy. In Ojibwe the bird is bibiigiwizens. Spanish also gives it the names cernícalo americano and halconcito colorado, the little red falcon.

In North American farming tradition the bird was the grasshopper hawk. In older American bird books it was the sparrow hawk, and that name held until 1983. In falconry tradition it is the bird a beginner learns on. Like other kestrels, it hovers, and European writers call that habit windhovering. Roland Wauer wrote a book about the species under the title falcon of many names.