American kestrels are the smallest falcons in North America. Males and females have different markings. Males have blue-gray wings and crowns, while females have reddish-brown wings and crowns. Juveniles of both genders look very similar to adult females. Adult males may have no spotting, or light spotting on the plumage of their upper breast, while juveniles have heavy streaking on their upper breast. As adults, males and females have a black and white pattern on their faces. They both have two black slashes on their faces, making it easy to tell them apart. Adults have a sharp, pointed beak. They also have long, pointed wings and tails, as well as large feet. (Bird, 1982; Elbroch and Marks, 2001; Negro, et al., 1998; Palmer, 1988; Parrish, et al., 1987; Smallwood, 1989; Stotz, et al., 1996)
American kestrels (Falco sparverius) are widespread throughout North and South America, they can be found from Alaska to the southern tip of South America. They are permanently found in 35 U.S states, the Gulf of California, northwest and central Mexico, and every country in South America except Brazil. They migrate, in the United States they are only found in Montana, North and South Dakota, Wyoming, Minnesota, Wisconsin, Michigan, central Alaska, and Maine in the summer for breeding. They may also migrate to Canada for the summer breeding season, they can be found in British Columbia, Alberta, Saskatchewan, Manitoba, New Brunswick, Nova Scotia, the Gulf of St. Lawrence, and parts of Ontario, Quebec, the Yukon, and the Northwest Territories. In the winter, American kestrels can be found in eastern Mexico and Central America. (Ardia and Bildstein, 1997; Palmer, 1988)
American kestrels can live in most habitat types found in their range including fields, cities, deserts, plains, mountains, and tropical lowlands. To live in a habitat successfully, they need areas for hunting, tall trees to perch in, and areas for nesting. They are most often found in open habitats and urban areas. (Ardia and Bildstein, 1997; Johnsgard, 1990; Palmer, 1988)
American kestrels pair bond and only mate with one individual. After making a nest, they begin courting. Pairs bond by using courtship rituals, such as flight displays and courtship feeding. After a relationship is developed, it becomes strong and usually permanent. Most pairs return to the same nesting sites each year. (Bortolotti and Wiebe, 1993; Dawson and Bortolotti, 2008; Johnsgard, 1990; Palmer, 1988; Steenhof and Peterson, 2009; Wiebe and Bortolotti, 2009)
American kestrels may breed at different times of the year, depending on their range, but most breed during the early spring to late summer. Breeding pairs search for nesting sites together, although males often make the final decisions. To protect their brood from predators, these falcons mostly nest in tree hollows, rock crevices, and the corners of buildings or other man-made structures such as telephone poles and fence posts. They typically raise one brood of 3 to 7 eggs per season, but they can raise two if the first brood is unsuccessful. Their average gestation period is 30 days. Chicks are ready for flight about 30 days after hatching, and become independent from their parents about three weeks later. (Bortolotti and Wiebe, 1993; Dawson and Bortolotti, 2008; Johnsgard, 1990; Palmer, 1988; Wiebe and Bortolotti, 2009)
Male and female American kestrels have different roles during the breeding season. Females are more likely to incubate the eggs, although males will also incubate the eggs when the females are not present. Males bring food for the mother and offspring from the time the female lays the eggs until she begins hunting for her own food, after the chicks are about 10 days old. After hatching, females protect their young and stay near the nest, while males begin leaving the nests more often. Chicks are born with a white downy coat and pink skin. Kestrels are born altricial, which means they are very dependent on their parents for food and protection. This dependence lasts about three weeks after fledging, when offspring are self-sufficient. (Bortolotti and Wiebe, 1993; Johnsgard, 1990; Palmer, 1988; Wiebe and Bortolotti, 2009)
In the wild, American kestrels live an average of 1 year and 3 months, however, the oldest known wild individual survived 11 years. They live an average of 5 years and 2 months in captivity, although they have been known to survive up to 17 years. American kestrels are mostly killed by illegal hunting and trapping, although they are also vulnerable to cars, predators, and diseases. (Clapp, et al., 1982; Monoghan and Metcalfe, 2000; Palmer, 1988; Roest, 1957)
Other than during mating season, American kestrels are solitary birds. They are aggressive towards other birds over prey, territory, and nesting sites. They show their aggression by making loud calls and circling and diving at other birds. Eventually, one of the birds will give up and leave the area. These falcons bathe in standing water or rain showers. To help control external parasites, they also take dust baths by splashing dust with their wings to cover their body. (Bird and Negro, 1996; Johnsgard, 1990; Palmer, 1988; Rudolph, 1982)
Their home range depends on the available nesting sites and resources, but ranges from 4.5 to 5.2 square kilometers. (Palmer, 1988)
American kestrels make three types of calls – the “klee” or “killy,” the “chitter,” and the “whine”. The "klee" is used all year by both males and females to communicate distress or excitement. Adult male and female birds give a friendly “chitter” call to the opposite sex, usually during courtship or breeding. The “whine” call usually has to do with feeding; it is used by adults and by hungry offspring. By the time they are 2 weeks old, they can give all 3 calls. American kestrels also communicate visually by making behavioral displays. (Johnsgard, 1990)
American kestrels have different diets seasonally. During the summer they mostly eat insects such as grasshoppers, crickets, butterflies, moths, and beetles. During the winter, they hunt small prey such as mice, voles, shrews, snakes, frogs, and small birds. In urban areas, their diets usually include 78% insects, 14% mammals, 6% reptiles and amphibians, and 3% birds. American kestrels hunt during the day with three different hunting types: hovering, perching, and in-flight insect catching. They are good hunters partially due to their talon-tipped feet and sharp beaks. (Bird, et al., 1982; Brack, et al., 1985; Johnsgard, 1990; Palmer, 1988; Rudolph, 1982)
Since American kestrels are small falcons, they may be preyed on by other raptors including great-horned owls, red-tailed hawks, and prairie falcons. Among American kestrels, mostly eggs, chicks, and young birds are preyed upon. American kestrels have two black spots on the back of their head, which may confuse predators because the black dots look like eyes. They may also be preyed on by bobcats, skunks, coyotes, and raccoons. Their keen eyesight helps them avoid predators. (Johnsgard, 1990; Palmer, 1988)
American kestrels host parasites such as trematodes (Ascocotyle felippei), mites (Epoplichus minor), nematodes (Baruscapillaria falconis), and protozoa (Plasmodium relictum). American kestrels may also carry avian malaria. Falcons also help disperse the seeds of some plants by eating them, and spreading them throughout their community. They also help control prey populations. (Gonzalez-Acuna, et al., 2011; Medica, et al., 2007)
American kestrels sometimes catch and eat small domesticated animals and pets such as chickens, cats, and small dogs. (Bird, 1982)
American kestrels are kept and trained by humans for the sport of falconry. In the United States, American kestrels and red-tailed hawks are the only birds used by beginner falconers. These birds are used to hunt rodents, insects, and small birds. American kestrels are also used in scientific research because they are easily bred in captivity. They are considered useful to humans, especially farm owners, because they eat pest species. (Bird, 1982; Medica, et al., 2007)
American kestrels have a stable population of more than 1,000,000 birds. They are considered a species of least concern around the world and are not listed as a species of concern in the United States. (BirdLife International, 2012; Strasser and Heath, 2013)
Sutton Townes (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
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