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Photo credit: Jean-Guy Dallaire

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The American Kestrel (Falco sparverius) is a small falcon.

Birds in northern Canada and Alaska migrate further south. This small falcon species is common in North America, but a very rare vagrant to western Europe.

This bird was formerly known as the Sparrow Hawk. This name was unfortunate because it implied a connection with the Old World Sparrowhawk Accipiter nisus, which is unrelated - the latter is a hawk rather than a falcon.

Description

American Kestrels are the smallest falcon in North America. These tiny, seemingly fearless birds are brightly adorned with reddish, blue and cinnamon colors. Both sexes have reddish and blue crowns. Males have blue wings and cinnamon or rusty backs and tails. The breast is white with dark spots. Females have a cinnamon body color with dark streaks. the breast is a lighter tan color with vertical brown streaks.

Adult males have a chestnut patch on top of the head; their wings are blue-grey, their belly is pale and their tail has a black band near the end. Adult females have chestnut wings with black bars and chestnut streaks on the breast; their heads are duller in colour.

They have white cheeks with two black vertical lines, one in front of the eye and one at the ear. They have long slim pointed wings, a blue-grey cap and a long chestnut tail. Their back is chestnut with black bars.

As with all raptors the females are larger than males, however the difference is slight. Lengths average 25 cm (10 inches) for females and 24 cm (nine inches) for males. Wingspans average 57 cm (22 inches) for females and 55 cm (21 inches) for males. Weights average 120 g (5 oz) for females and 111 g (3.5 oz for males.

Identification Tips

American Kestrels are a small raptor - about the size of a robin and one of the few raptors where there is a color difference between the male and female. Both sexes have reddish and blue crowns. Males have blue wings and cinnamon or rusty backs and tails. The breast is white with dark spots. The breast of the female is a lighter tan color with vertical brown streaks. As with all falcons they have long, pointed wings when seen in flight. The are also commonly seen sitting on phone and electrical wires between the poles.

Habitat

American Kestrels are found in a variety of habitats including parks, suburbs, open fields, forest edges and openings, alpine zones, grasslands, marshes, open areas on mountainsides, prairies, plains, deserts with giant cacti, and freeway & highway corridors. In addition to requiring open space for hunting, American kestrels seem to need perches for hunting from, cavities for nesting (either natural or man-made), and a sufficient food supply. In Idaho they can be found in both urban and rural areas.

Range

American Kestrels are widely distributed across the Americas. Their breeding range extends as far north as central and western Alaska across northern Canada to Nova Scotia, and extends south throughout North America, into central Mexico, the Baja, and the Caribbean. They are local breeders in Central America and are widely distributed throughout South America. Most of the birds breeding in Canada and the northern United States migrate south in the winter, although some males stay as year round residents.

Behavior

The American Kestrel is the only North American falcon to habitually hover with rapid wing beats, keeping its head motionless while scanning the ground for prey. The kestrel commonly perches along fences and powerlines. It glides with flat wings and wingtips curved upward. It occasionally soars in circles with its tail spread and its wings flat.

Several hunting techniques are used by the American Kestrel. It will hover over one spot—when prey is sighted the kestrel will partly fold its wings and drop lower once or several times before striking. When the prey disappears the falcon will glide in a semicircle before turning back into the wind to hover again. It will also soar in circles, or figure eights, using the same stooping tactics as when hovering. The kestrel commonly hunts from elevated perch sites, waiting for prey to move on the ground. The kestrel bobs its head and pumps its tail just before attacking. Other prey capture techniques include direct pursuit, landing and flushing prey from the ground (especially for grasshoppers)and then taking them in flight, capturing flying insects from an elevated perch, and nest robbing including the burrows of Bank Swallows and the nests of Cliff Swallows. It is also an occasional bat catcher, taking bats from their tree roosts, or striking bats in flight from above or as the bats leave or enter caves. The kestrel will kill and cache food items.

The American Kestrel is migratory over much of the northern half of its North American breeding range. Returning individuals commonly re-establish territories held the previous year. In one study, a pair nested in the same tree for six consecutive years.

Because it feeds on both insects and vertebrates, the American Kestrel maintains fairly high population densities. It has a small breeding home range, from 1.75 to 2 square miles. Territory size has been estimated at 269 to 321 acres with much larger wintering home ranges.

The American Kestrel occasionally robs one another. This species has also been known to rob a shrike of its prey. Kestrels sometimes harass other hawks, and even Golden Eagles, in flight. The American Kestrel will vigorously defend its nest against other cavity nesters.

Nesting

The American Kestrel is double-brooded, particularly in the southern United States, in areas of abundant small mammals. Replacement clutches can be laid.

A cavity nester, American Kestrels will use holes in trees, artificial nest boxes, or small spaces in buildings. Kestrels in the NCA usually nest in small rock cavities and crevices in cliffs. The number of suitable breeding cavities limits this species' breeding density. The American Kestrel has adapted well to nest boxes. In one program, nest boxes were fixed to the backs of signs along a freeway thus allowing kestrels to breed in areas formerly devoid of nest sites. Pairs nesting in boxes on poles have much higher nesting success than pairs using boxes on trees. No nest is built inside. In nest boxes sawdust and wood shavings may be a suitable substrate for the eggs

Both sexes take turns incubating their eggs, a very rare situation among North American birds of prey where the female usually incubates exclusively. Both sexes develop bare oval patches on each side of their breasts where the warm bare skin can contact the eggs for warming. Eggs hatch about 30 days after being laid. There are from three to seven eggs laid, but four to six are average. The eggs are typically short elliptical in shape, and are white or pinkish-white with an even covering of fine spots and flecks of brown shades, occasionally concentrating as a ring or a cap. They will renest if the first nest fails and have been reported to raise 2 broods per year in some of the southern states.

The young grow very quickly, becoming noisy between day 11 and 14 and assuming adult weight in about 2.5 weeks. The young take their first flight between days 26 and 31. Early fledgling behavior varies. Broods typically stay together for a week or two. Some broods remain close to the nest area for a week or two while others travel throughout the parents' home range. Generally, young do not disperse more than 0.6 miles (one km) away from the nest area until two to four weeks old. Young disperse as hunting skills develop. Occasionally groups of older juveniles from various broods join together into flocks.

Food/Diet

In summer, kestrels feed largely on grasshoppers, dragonflies, lizards, mice, and voles. They will also eat other small birds. Wintering birds feed primarily on rodents and birds. The birds characteristically hunt along roadsides from telephone wires, fence posts, trees or other convenient perches when not actually flying in search of food. When they are flying and looking for food they frequently hover with rapid wingbeats.

Voice

The American Kestrel has three basic vocalizations - the "klee" or "killy", the "whine", and the "chitter." The "klee" or "killy" is usually delivered as a rapid series - "killy, killy, killy, killy" when the kestrel is upset or excited. It is used at the apex of the dive display, during fights with other kestrels, and after unsuccessful hunting attempts.

The "whine" may last as long as one to two minutes and may be single or treble. The more intense the situation, the more likely the "whine" will move toward the treble extreme. "Whines" are given during courtship feeding and copulation. The treble whine is heard from breeding females and fledged hungry young.

The "chitter" is the most frequent vocalization in male - female interactions. Its volume and duration depends upon the stress or excitement of the situation. It is associated with friendly approaches and bodily contact between the sexes during breeding season. Occasionally a "chitter" follows a "whine."

Calling occurs throughout the day. Nestlings at two weeks can produce all three vocalizations. Female kestrels tend to have slightly lower pitched and harsher voices than males.

Reproduction/Life Span

Kestrels form pairs in which the bond is strong, tending toward permanence. Courtship begins shortly after the male establishes a territory. In early courtship, he may give the "dive display", a series of climbs and dives 33 to 66 feet (10 to 20 m) with 3-5 "klee" notes given near the peak of each climb. He may present the female with food during courtship feeding. He may entice her to the nest site by calling. He may "flutter-glide" toward her with quick and shallow wing beats while carrying food and she may also beg for food by flutter-gliding. The female initiates copulation by bowing with her tail in line with her body or slightly raised.

The American Kestrel is not long-lived. The oldest banded wild bird was 11 years and seven months old while a captive lived 14 years. A mortality rate average of 57 percent was found. First year mortality rates have declined since 1945 with a decrease in shooting. Major causes of death include collision with traffic, illegal shooting, and predation by other raptors, including the red-tailed hawk, Northern goshawk, Cooper's hawk, peregrine falcon, barn owl, and great horned owl.

Conservation

The American Kestrel's North American population has been estimated at 1.2 million pairs, with the Central and South American populations being as large. It is possible that the clearing of parts of North America for agriculture in the last two hundred years has caused the American kestrel population to increase. The southeastern race, Falco sparverius paulus, is in serious decline (an 82 percent decrease since the early 1940s in north central Florida) possibly due to habitat loss and loss of nest sites, and has been listed in Florida as "threatened." Threats to the species as a whole include loss of nest sites, pesticide poisoning (including dieldrin and DDT among others), and death through collisions with vehicles as well as shooting.

The species responds very well to nest box programs which can dramatically increase nesting densities in areas where kestrels were formerly scarce. Nest boxes may also increase the number of wintering kestrels by acting as shelters and roost sites. The American kestrel is an adaptable species which can survive in suburban areas, given proper nesting sites.

Observing American Kestrels

One of the best places to view the American kestrel is in the Snake River Birds of Prey National Conservation Area (NCA) in Idaho. Birds in the NCA are not on display. They follow the rhythms of nature and not the desires of people who come to see them. In and around the NCA if you see a small bird "hovering", it's a kestrel. Your chance of seeing the falcons will improve if you follow these tips:

*Bring a good pair of binoculars. Field guides or spotting scopes are also helpful.

*Viewing tends to be best in mid-March, May and June, in the early morning and evening hours when the falcons are actively hunting.

*During April, viewing opportunities slow as birds spend most of their time sitting on nests.

*By July, the canyon temperatures are fiercely hot, ground squirrels have gone back underground and many birds of prey have left the area.

*Wildlife are wary of humans. Patience is a wildlife watcher's best virtue. When an animal changes behavior as a result of your presence, you are too close.

References

*This article incorporates text from the Bureau of Land Management, which is in the Public domain.

External links

* American Kestrel videos on the Internet Bird Collection