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American kestrel

Falco sparverius

What do they look like?

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)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    80 to 165 g
    2.82 to 5.81 oz
  • Range length
    22 to 31 cm
    8.66 to 12.20 in
  • Range wingspan
    51 to 61 cm
    20.08 to 24.02 in

Where do they live?

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)

What kind of habitat do they need?

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)

  • Range elevation
    0 to 3690 m
    0.00 to 12106.30 ft

How do they reproduce?

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)

  • How often does reproduction occur?
    American falcons breed once yearly.
  • Breeding season
    Their breeding season may vary with their range, but most populations breed in the early spring to late summer.
  • Range eggs per season
    3 to 7
  • Average eggs per season
    5
    AnAge
  • Range time to hatching
    26 to 32 days
  • Average time to hatching
    30 days
  • Range fledging age
    28 to 32 days
  • Range time to independence
    28 to 32 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    365 days
    AnAge

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)

How long do they live?

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)

  • Average lifespan
    Status: wild
    11 years
  • Average lifespan
    Status: captivity
    17 years
  • Typical lifespan
    Status: wild
    0 to 11 years
  • Average lifespan
    Status: wild
    1 years
  • Typical lifespan
    Status: captivity
    0 to 17 years
  • Average lifespan
    Status: captivity
    5 years

How do they behave?

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)

  • Average territory size
    4.5-5.2 km^2

Home Range

Their home range depends on the available nesting sites and resources, but ranges from 4.5 to 5.2 square kilometers. (Palmer, 1988)

How do they communicate with each other?

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)

What do they eat?

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)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • insects
  • terrestrial non-insect arthropods
  • terrestrial worms

What eats them and how do they avoid being eaten?

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)

What roles do they have in the ecosystem?

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)

  • Ecosystem Impact
  • disperses seeds
  • pollinates
Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • trematodes (Ascocotyle felippei)
  • mites (Epoplichus minor)
  • protozoans (Plasmodium relictum)
  • nematodes (Baruscapillaria falconis)

Do they cause problems?

American kestrels sometimes catch and eat small domesticated animals and pets such as chickens, cats, and small dogs. (Bird, 1982)

How do they interact with us?

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)

  • Ways that people benefit from these animals:
  • research and education
  • controls pest population

Are they endangered?

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)

Some more information...

American kestrels were formerly known as American sparrow hawks. They were officially renamed in 1983 by the American Ornithologist's Union. (Palmer, 1988; Roest, 1957)

Contributors

Sutton Townes (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

References

Ardia, D., K. Bildstein. 1997. Sex-related differences in habitat selection in wintering American kestrels, Falco sparverius. Animal Behavior, 53: 1305-1311.

Bird, D. 1982. The American kestrel as a laboratory research animal. Nature, 299: 300-301.

Bird, D., S. Ho, D. Pare. 1982. Nutritive values of three common prey items of the American kestrel. Comparative Biochemistry and Physiology, 73A/3: 513-515.

Bird, D., J. Negro. 1996. Social behavior of captive fledging American kestrels (Falco sparverius). Journal of Raptor Research, 30/4: 240-241.

BirdLife International, 2012. "Falco sparverius" (On-line). IUCN Red List of Threatened Species. Accessed November 01, 2013 at http://www.iucnredlist.org/details/22696395/0.

Bortolotti, G., K. Wiebe. 1993. Incubation behaviour and hatching patterns in the American kestrel (Falco sparverius). Ornis Scandinavica, 24/1: 41-47.

Brack, V., T. Cable, D. Driscoll. 1985. Food habits of urban American kestrels. Zoology, 94/1: 607-613.

Clapp, R., K. Klimkiewicz, J. Kennard. 1982. Longevity records of North American birds: Gaviidae through Alcidae. Journal of Field Ornithology, 53/2: 81-208.

Dawson, R., G. Bortolotti. 2008. Experimentally prolonging the brood-rearing period reveals sex-specific parental investment strategies in American kestrels (Falco sparverius). The Auk, 125/4: 889-895.

Elbroch, M., E. Marks. 2001. Bird Tracks & Sign - A Guide to North American Species. Machanicsburg, PA: Stackpole Books.

Gonzalez-Acuna, D., E. Lohse, A. Cicchino, S. Mironov, R. Figueroa, K. Ardiles, M. Kinsella. 2011. Parasites of the American kestrel (Falco sparverius) in south-central Chile. Journal of Raptor Research, 45/2: 188-193.

Johnsgard, P. 1990. Hawks, Eagles, and Falcons of North America. United States: Smithsonian Institution.

Medica, D., R. Clauser, K. Bildstein. 2007. Prevalence of West Nile virus antibodies in a breeding population of American kestrels (Falco sparverius) in Pennsylvania. Journal of Wildlife Diseases, 43/3: 538-541.

Monoghan, P., N. Metcalfe. 2000. Genome size and longevity. Trends in Genetics, 16/8: 331-332.

Negro, J., G. Bortolotti, J. Tella, K. Fernie, D. Bird. 1998. Regulation of integumentary colour and plasma carotenoids in American kestrels consistent with sexual selection theory. Functional Ecology, 12: 307-312.

Palmer, R. 1988. Handbook of North American Birds Volume 5. Yale University: Yale University Press.

Parrish, J., J. Stoddard, C. White. 1987. Sexually mosaic plumage in a female American kestrel. The Condor, 89/4: 911-913.

Roest, A. 1957. Notes on the American sparrow hawk. The Auk, 74/1: 1-19.

Rudolph, S. 1982. Foraging strategies of American kestrels during breeding. Ecology, 63/5: 1268-1276.

Smallwood, J. 1989. Age determination of American kestrels: A revised key. Journal of Field Ornithology, 60/4: 510-519.

Steenhof, K., B. Peterson. 2009. Site fidelity, mate fidelity, and breeding dispersal in American kestrels. The Wilson Journal of Ornithology, 121/1: 12-21.

Stotz, D., J. Fitzpatrick, T. Parker, D. Moskovits. 1996. Neotropical Birds: Ecology and Conservation. United States: The University of Chicago Press.

Strasser, E., J. Heath. 2013. Reproductive failure of a human-tolerant species, the American kestrel, is associated with stress and human disturbance. Journal of Applied Ecology, 50: 912-919.

Wiebe, K., G. Bortolotti. 2009. Egg size and clutch size in the reproductive investment of American kestrels. Journal of Zoology, 237/2: 285-301.

Wiehn, J., E. Korpimaki, K. Bildstein, J. Sorjonen. 1997. Mate choice and reproductive success in the American kestrel: A role for blood parasites?. Ethology, 103: 304-317.

 
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Townes, S. 2014. "Falco sparverius" (On-line), Animal Diversity Web. Accessed September 02, 2014 at http://www.biokids.umich.edu/accounts/Falco_sparverius/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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