The American Kestrel
By Steve Bryant, Wildlife Biologist
The American kestrel, commonly called the sparrow hawk, is more accurately described as a falcon. Falcons are distinguished from other birds commonly called hawks in that they have relatively large heads, broad shoulders, long pointed wings and long tails. The American kestrel is the most widely distributed and numerous of the falcons on the American Continent, ranging from southern Alaska through western Canada, throughout the contiguous 48 states and south through Mexico, Central American and South America.
It is the smallest of the falcons, with adults ranging from 8 to 11 inches in length. Both sexes are very colorful and distinctly marked. Identifying characteristics of the kestrel are a small falcon with a rufous back and rufous tail.
The Kestrel is commonly sighted perched on a utility line, fence, post, or a tree overlooking its preferred habitat of open land such as fields, meadows or pastures. In the arid western states, it also inhabits deserts. It is sometimes seen in residential areas but rarely in cities or the interior of forests.
The kestrel employs two types of hunting techniques. The most common is remaining perched in a location that provides a good view of the surrounding landscape. At other times, the kestrel will face into the wind and hover by flapping its wings as it surveys the terrain below. Its eyesight has been estimated to be approximately eight times stronger than humans. When prey is spotted, it attacks by partially folding its wings making a swooping dive; just before impact it will spread its wings and tail to brake, grasping the quarry in its talons. American kestrels employ a kicking motion as it seizes its prey, which serves to increase the velocity of the actual attack, making it more lethal. A kestrel will return to its perch to consume its prey. The kestrel is an opportunistic feeder, preying on what ever is easily caught. This includes crickets, beetles, grasshoppers and other insects, small reptiles or amphibians, mice, voles, rats and small birds. Researchers have discovered that the young of other birds appear to be the choice food for fledging kestrels. At other times during the warm months, insects and mice are key food items. During the winter, the diet is predominately small rodents. The kestrel’s diet benefits humans because it utilizes insects and small rodents that are generally destructive.
American kestrels begin pairing for mating in February in the southern states, around April in the middle states and progressively later as latitude increases. Kestrels in the southern states usually raise two sets of young per year, while those in more northern latitudes attempt only one nest. The male will make short flights in search of a receptive female. After a female is located, courtship begins. Courtship behaviors include mutual preening while perched, touching of beaks and nibbling the mate’s toes. Kestrels also engage in courtship flights or chases where they touch beaks or grasp feet while in flight. Sometimes they will fly circles around each other. The female also does a flutter glide that stimulates the male to offer her food. During courtship they can be heard making the call kille, kille, kille.
The male takes the responsibility of locating a suitable nest site. American kestrels are cavity nesters. Suitable nesting locations include natural cavities in trees, abandoned woodpecker holes, niches in cliffs, or holes in the walls of deserted buildings. Nest boxes that are built specifically for kestrels are eagerly used. The dimensions suitable for a kestrel nest box are one foot deep and wide with a height of 16 inches. A four-inch round hole should be placed 8 to 12 inches above the floor of the box. Narrow spaces should be left between the top and the sides of the box to improve ventilation. Some small holes drilled in the bottom will allow for drainage. Sawdust in the bottom will give the hen a soft place to lay her eggs.
Males locate prospective nest sites, which are inspected and approved by the female before egg laying begins. Once laying commences, females will lay one egg, approximately every other day until a clutch of four to six eggs is completed. Kestrel eggs are round, pale brownish in color with darker brown and black splotches. Both the male and the female incubate the eggs, alternately taking turns, feeding each other and watching for danger. Kestrels establish a territory around the nest of approximately one-half square mile. If intruders enter the territory the kestrel will pursue them screaming kille, kille, kille.
Eggs are incubated for approximately one month before hatching. The parents feed and care for the young for another month until they fledge. After the young kestrels leave the nest, they remain with the parents for up to another month. They hunt as a family unit, each taking their perch around a field to watch for prey. Kestrels form such an attraction for a favorable perch that they may use it for months. Many kestrels migrate south for the colder months; however, some have been known to winter in the northern U.S. Those that remain in the northern latitudes for the winter usually associate with an agricultural setting.
To view video of American kestrels at the Alabama Capitol, visit www.outdooralabama.com/outdoor-alabama-tv/video.cfm. Scroll down until you see the "American Kestrels Nest in State Capitol" title.