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The American kestrel (''Falco sparverius''), also called the sparrow hawk, is the smallest and most common
falcon Falcons () are birds of prey in the genus ''Falco'', which includes about 40 species. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene. Adult falcons ...
in North America. It has a roughly two-to-one range in size over subspecies and sex, varying in size from about the weight of a
blue jay The blue jay (''Cyanocitta cristata'') is a passerine bird in the family Corvidae, native to eastern North America. It lives in most of the eastern and central United States; some eastern populations may be migratory. Resident populations are ...
to a mourning dove. It also ranges to South America and is a well-established species that has evolved into 17 subspecies adapted to different environments and habitats throughout the Americas. It exhibits
sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
in size (females being moderately larger) and
plumage Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
, although both sexes have a
rufous Rufous () is a color that may be described as reddish-brown or brownish-red, as of rust or oxidised iron. The first recorded use of ''rufous'' as a color name in English was in 1782. However, the color is also recorded earlier in 1527 as a dia ...
back with noticeable barring. Its plumage is colorful and attractive, and juveniles are similar in plumage to adults. The American kestrel usually hunts in energy-conserving fashion by perching and scanning the ground for prey to ambush, though it also hunts from the air. It sometimes hovers in the air with rapid wing beats while homing in on prey. Its diet typically consists of
grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...
s and other insects,
lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...
s, mice, and small birds (e.g.
sparrows Sparrow may refer to: Birds * Old World sparrows, family Passeridae * New World sparrows, family Passerellidae * two species in the Passerine family Estrildidae: ** Java sparrow ** Timor sparrow * Hedge sparrow, also known as the dunnock or he ...
). This broad diet has contributed to its wide success as a species. It nests in cavities in trees, cliffs, buildings, and other structures. The female lays three to seven eggs, which both sexes help to incubate. Its breeding range extends from central and western
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...
across northern Canada to
Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...
, and south throughout North America, into central
Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
and the
Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean ...
. It is a local breeder in Central America and is widely distributed throughout South America. Most birds breeding in Canada and the northern United States migrate south in the winter. It is an occasional vagrant to Western Europe. Based on appearance and behavior it was for many years considered a member of the primarily European and African kestrel
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
within the genus ''Falco'', but DNA analysis shows the American kestrel to actually be genetically more closely related to the larger American falcons such as the aplomado,Wink, M., and H. Sauer-Gürth (2004) "Phylogenetic relationships in diurnal raptors based on nucleotide sequences of mitochondrial and nuclear marker genes", pp. 483–498 in R.D. Chancellor and B.-U. Meyburg (eds.) ''Raptors Worldwide'', World Working Group on Birds of Prey, Berlin. peregrine, and
prairie falcon The prairie falcon (''Falco mexicanus'') is a medium-large sized falcon of western North America. It is about the size of a peregrine falcon or a crow, with an average length of 40 cm (16 in), wingspan of approximately 1 meter (40&n ...
s. Though the species has not been renamed as a result of these genetic analyses, it is not actually a
kestrel The term kestrel (from french: crécerelle, derivative from , i.e. ratchet) is the common name given to several species of predatory birds from the falcon genus ''Falco''. Kestrels are most easily distinguished by their typical hunting behaviou ...
in the
phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...
sense. Instead, a process of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
to fit a similar small prey niche in the ecosystem as the true kestrels have left it with similar physical characteristics and hunting methods. The American kestrel is a common bird used in
falconry Falconry is the hunting of wild animals in their natural state and habitat by means of a trained bird of prey. Small animals are hunted; squirrels and rabbits often fall prey to these birds. Two traditional terms are used to describe a person ...
, especially by beginners. Though not as strong a flyer as many other, larger falcons, proper training and weight control by the falconer allows many American kestrels to become effective hunters of birds in the size range of sparrows and starlings, with occasional success against birds up to approximately twice their own weight.


Description

Under traditional classification, the American kestrel is the smallest raptor in America. The American kestrel is sexually dimorphic, although there is some overlap in plumage coloration between the sexes. The bird ranges from in length with a wingspan of . The female kestrel is larger than the male, though less so than larger falcons, being typically about 10% to 15% larger within a subspecies. The more northern subspecies tend to larger sizes (northern hemisphere), with a large northern female being about twice the size of a small southern male. The male typically weighs , and the female . In standard measurements, the wing bone is long, the tail is and the tarsus is . Physically, American kestrels are leaner and less muscular than larger falcons.Mullenix, Matt (2003
Merlins and American Kestrels Compared
merlinfalconry.com.
The pectoral flight muscles of the American kestrel make up only about 12% of its body weight, as compared to about 20% for the strongest flying falcons such as the peregrine. The wings are moderately long, fairly narrow, and taper to a point. Their less muscular body type is adapted to energy-conserving ambush hunting, rather than spending large amounts of energy-consuming time on the wing and getting into long tail-chases of bird prey. For their size, they have strong talons and beaks, and can swiftly dispatch prey. Their lean build and energy-conserving strategy allow a lower daily food intake than if they were more strongly muscled, yet with enough strength to commonly take bird prey as large as themselves, and occasionally larger. The success of this body style and hunting strategy is reflected in the high success of the species in densely populating a large range throughout the Americas. The flight of the American kestrel is not so dramatic and swift as more muscular falcons such as merlins and peregrines, but their efficient adaptation to a broader diet of more available smaller prey, and need for less food per day, has resulted in there being many more of them. In contrast to many other raptor species, the sexes differ more in plumage than in size. Males have blue-grey
wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is e ...
s with black spots and white undersides with black barring. The back is
rufous Rufous () is a color that may be described as reddish-brown or brownish-red, as of rust or oxidised iron. The first recorded use of ''rufous'' as a color name in English was in 1782. However, the color is also recorded earlier in 1527 as a dia ...
, with barring on the lower half. The belly and flanks are white with black spotting. The tail is also rufous, with a white or rufous tip and a black subterminal band. The back and wings of the female American kestrel are rufous with dark brown barring. The undersides of the females are creamy to buff with heavy brown streaking. The tail is noticeably different from the male's, being rufous in color with numerous narrow dark black bars. Juveniles exhibit coloration patterns similar to the adults'. In both sexes, the head is white with a bluish-grey top. There are also two narrow, vertical black facial markings on each side of the head, while other falcons have one. Two black spots (ocelli) can be found on each side of the white or orangish nape. The function of these spots is debated, but the most commonly accepted theory is that they act as "false eyes", and help to protect the bird from potential attackers.


Vocalizations

The American kestrel has three basic vocalizations – the "klee" or "killy", the "whine", and the "chitter". The "klee" is usually delivered as a rapid series – ''klee, klee, klee, klee'' when the kestrel is upset or excited. This call is used in a wide variety of situations and is heard from both sexes, but the larger females typically have lower-pitched voices than the males. The "whine" call is primarily associated with feeding but is also uttered during
copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...
. The "chitter" is used in activities that involve interaction between male and female birds, including
courtship feeding A nuptial gift is a nutritional gift given by one partner in some animals' sexual reproduction practices. Formally, a nuptial gift is a material presentation to a recipient by a donor during or in relation to sexual intercourse that is not simpl ...
, copulation, and the feeding of nestlings. Nestlings can produce calls similar to those of adults at 16 days old.


Taxonomy

Until the sixth edition of the AOU Checklist of North American Birds was published by the
American Ornithologists' Union The American Ornithological Society (AOS) is an ornithological organization based in the United States. The society was formed in October 2016 by the merger of the American Ornithologists' Union (AOU) and the Cooper Ornithological Society. Its ...
in 1983, the most commonly used name for the American kestrel was the ''sparrow hawk''. This was due to a mistaken connection with the
Eurasian sparrowhawk The Eurasian sparrowhawk (''Accipiter nisus''), also known as the northern sparrowhawk or simply the sparrowhawk, is a small bird of prey in the family Accipitridae. Adult male Eurasian sparrowhawks have bluish grey upperparts and orange-barr ...
in the genus ''
Accipiter ''Accipiter'' is a genus of birds of prey in the family Accipitridae. With 51 recognized species it is the most diverse genus in its family. Most species are called goshawks or sparrowhawks, although almost all New World species (excepting th ...
''. The sixth edition of the AOU Checklist corrected this, officially renaming the bird ''American kestrel''. Several other colloquial names for the kestrel are also in use, including ''grasshopper hawk'', due to its diet, and ''killy hawk'', due to its distinct call. Wauer, p. 4 As noted in the introduction, DNA analysis shows the American kestrel to actually be genetically more closely related to the larger American falcons than to the true kestrels. However, based on its physical similarity to the kestrels and the established nature of the name American kestrel, there has been little impetus to change its name. This could change in the future if continued genetic research more precisely determines the evolutionary history of the American kestrel within the genus ''Falco''. The entire genus is actually a set of species so closely related that most or all can be hybridized by artificial insemination. Significant natural hybridization of species has occurred in the past during the evolution of this closely related set of species, such that precise evolutionary genetic analysis as to which species are more basal to other species or to the genus as a whole is difficult to render. The American kestrel's scientific name, ''Falco sparverius'', was given by
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...
in his 18th century work ''
Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial ...
''. The genus refers to the falcate, or hooked, shape of the beak, and the specific name means "pertaining to a sparrow", referring to the bird's small size and hunting of sparrows as a typical prey. Seventeen subspecies of the American kestrel are recognized, generally based upon plumage, size, and vocalizations: *''F. s. sparverius'', described by
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...
in
1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of ''Systema Naturae'', the starting point of modern zoologi ...
, is the
nominate subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all speci ...
. It is found in most of the United States, Canada and Mexico. *''F. s. paulus'', described by Howe and King in 1902, is found in the southeastern United States from
Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is bord ...
to Florida. *''F. s. peninsularis'', described by
Edgar Alexander Mearns Edgar Alexander Mearns (September 11, 1856 – November 1, 1916) was an American surgeon, ornithologist and field naturalist. He was a founder of the American Ornithologists' Union. Life Mearns was born in n Highland Falls, New York to Alex ...
in 1892, is found in southern
Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
. *''F. s. tropicalis'', described by Ludlow Griscom in 1930, is found from southern Mexico to northern
Honduras Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Oce ...
. *''F. s. nicaraguensis'', described by Howell in 1965, is found in Honduras and
Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the coun ...
. *''F. s. sparveroides'', described by
Nicholas Aylward Vigors Nicholas Aylward Vigors (1785 – 26 October 1840) was an Irish zoologist and politician. He popularized the classification of birds on the basis of the quinarian system. Early life Vigors was born at Old Leighlin, County Carlow on 1785 a ...
in 1827, is found on
Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribb ...
, Isla de Juventud and the central and southern
Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the a ...
. *''F. s. dominicensis'', described by
Johann Friedrich Gmelin , fields = , workplaces = University of GöttingenUniversity of Tübingen , alma_mater = University of Tübingen , doctoral_advisor = Philipp Friedrich Gmelin Ferdinand Christoph Oetinger , academic_advisors = , docto ...
in 1788, is found on
Hispaniola Hispaniola (, also ; es, La Española; Latin and french: Hispaniola; ht, Ispayola; tnq, Ayiti or Quisqueya) is an island in the Caribbean that is part of the Greater Antilles. Hispaniola is the most populous island in the West Indies, and th ...
(both the
Dominican Republic The Dominican Republic ( ; es, República Dominicana, ) is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean region. It occupies the eastern five-eighths of the island, which it shares with ...
and
Haiti Haiti (; ht, Ayiti ; French: ), officially the Republic of Haiti (); ) and formerly known as Hayti, is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean Sea, east of Cuba and Jamaica, and s ...
) and
Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of Hispa ...
. *''F. s. caribaearum'', described by Gmelin in 1788, is found on
Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and unincorporated ...
and throughout the
Lesser Antilles The Lesser Antilles ( es, link=no, Antillas Menores; french: link=no, Petites Antilles; pap, Antias Menor; nl, Kleine Antillen) are a group of islands in the Caribbean Sea. Most of them are part of a long, partially volcanic island arc be ...
to
Grenada Grenada ( ; Grenadian Creole French: ) is an island country in the West Indies in the Caribbean Sea at the southern end of the Grenadines island chain. Grenada consists of the island of Grenada itself, two smaller islands, Carriacou and Pet ...
. *''F. s. brevipennis'', described by Hans von Berlepsch in 1892, is found in the
Netherlands Antilles nl, In vrijheid verenigd"Unified by freedom" , national_anthem = , common_languages = Dutch English Papiamento , demonym = Netherlands Antillean , capital = Willemstad , year_start = 1954 , year_end = 2010 , date_start = 15 December , ...
. *''F. s. isabellinus'', described by
William John Swainson William John Swainson FLS, FRS (8 October 1789 – 6 December 1855), was an English ornithologist, malacologist, conchologist, entomologist and artist. Life Swainson was born in Dover Place, St Mary Newington, London, the eldest son of Jo ...
in 1837, is found from
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...
to northern
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
. *''F. s. ochraceus'', described by Charles B. Cory in 1915, is found in eastern
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the ...
and northwestern
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...
. *''F. s. caucae'', described by Frank Chapman in 1915, is found in western Colombia. *''F. s. aequatorialis'', described by Mearns in 1892, is found in northern
Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ' ...
. *''F. s. peruvianus'', described by Cory in 1915, is found in southwestern Ecuador,
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = National seal , national_motto = "Firm and Happy f ...
and northern
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...
. *''F. s. fernandensis'', described by Chapman in 1915, is found on the
Juan Fernández Islands The Juan Fernández Islands ( es, Archipiélago Juan Fernández) are a sparsely inhabited series of islands in the South Pacific Ocean reliant on tourism and fishing. Situated off the coast of Chile, they are composed of three main volcanic ...
off Chile. *''F. s. cinnamominus'', described by Swainson in 1837, is found in Peru, Chile and
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
. *''F. s. cearae'', described by Cory in 1915, is found from northeastern Brazil south to eastern
Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...
. File:Male American Kestrel.jpg, Male upperparts pattern File:American kestrel (Falco sparverius).jpg, ''F. s. dominicensis'',
Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of Hispa ...
File:American kestrel (Falco sparverius sparveroides) male red morph.JPG, ''F. s. sparveroides''
male red morph,
Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribb ...
File:American kestrel (Falco sparverius sparveroides) female white morph.JPG, ''F. s. sparveroides''
female white morph,
Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribb ...
File:American kestrel-Midwest.JPG, Perched in central
Illinois Illinois ( ) is a state in the Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolitan areas include, Peoria and Rock ...
File:20210506-DSC 3800.jpg, alt=Male showing female a nest box and offering mouse – Maine, Male showing female a nest box and offering mouse – Maine File:20200704-DSC 1454.jpg, alt=Female feeding nestling – Maine, Female feeding nestling – Maine File:20200707-DSC 1815.jpg, alt=Just fledged male, Just fledged male – Maine


Ecology and behavior

American kestrels are found in a wide variety of habitats, including
grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
s,
meadow A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non- woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or arti ...
s,
desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...
s and other open to semi-open regions. They can also be found in both urban and suburban areas. A kestrel's habitat must include perches, open space for hunting, and cavities for nesting (whether natural or man-made). The American kestrel is able to live in very diverse conditions, ranging from above the Arctic Circle, to the tropics of Central America, to elevations of over in the
Andes Mountains The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
. The bird is distributed from northern Canada and Alaska to the southernmost tip of South America,
Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla ...
. It is the only kestrel found in the Americas, though as mentioned above this classification is genetically inaccurate. It has occurred as a vagrant in the UK, Denmark, Malta and the
Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...
. American kestrels in Canada and the northern United States typically migrate south in the winter, some of them converging with resident kestrels of smaller size in Mexico, sometimes going as far as Central America and the Caribbean. Birds that breed south of about 35° north latitude are usually year-round residents. Migration also depends on local weather conditions. American Kestrels breeding at lower latitudes – below 48ºN to be precise – arrive earlier after warmer springs, whereas birds from higher latitudes return to their breeding grounds at the same time each year. These patterns suggest that short-distance migrants are better able to cope with climate change. Wintering kestrels' choice of habitat varies by sex. Females are found in open areas more often than males during the non-breeding season. A common explanation for this behavior is that the larger females who are bigger than the males arrive at the preferred habitat first and exclude males from their territory. The American kestrel is not long-lived, with a lifespan of <5 years for wild birds. The oldest banded wild bird was 11 years and 7 months, while captive kestrels can live up to 14–17 years. In a study, humans accounted for 43.2% of 1,355 reported deaths, which included direct killing and roadkills, while predation (including by larger birds of prey) accounted for 2.8%. This statistic is likely biased, however, as reported deaths are usually found near or in areas populated by humans.


Feeding

American kestrels feed largely on small animals such as
grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...
s,
cricket Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by st ...
s,
butterflies Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprises ...
,
moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
s,
dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threa ...
,
beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s,
lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...
s,
mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus'' ...
,
vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...
s,
shrew Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to differ ...
s,
frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s, and small birds. The kestrel has also been reported to have killed
scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always en ...
s,
snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...
s, bats, and
squirrel Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. ...
s. The kestrel is able to maintain high population densities, at least in part because of the broad scope of its diet. The American kestrel's primary mode of hunting is by perching and waiting for prey to come near. The bird is characteristically seen along roadsides or fields perched on objects such as trees,
overhead power line An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...
s, or fence posts. It also hunts by kiting, hovering in the air with rapid wing beats and scanning the ground for prey. Other hunting techniques include low flight over fields, or chasing insects and birds in the air. Prey is most often caught on the ground, though occasionally they take birds in flight. Before striking, the kestrel characteristically bobs its head and tail, then makes a direct flight toward the prey to grab it in its talons. Much like the
red-tailed hawk The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members wit ...
, American kestrels conserve energy in a hunt and pick their attacks with care as to position and odds of success. During the breeding season, the bird will carry large prey back to its mate or young. One study found that an American kestrel pair "foraged in ways that minimized the costs of energy acquisition in its particular situation". For example, if the success rate for catching prey decreases significantly in a particular area, the bird will move to a different area.


Reproduction

American kestrels are sexually mature by their first spring. In migratory populations, the males arrive at the breeding ground before females, then the female selects a mate. Pair bonds are strong, often permanent. Pairs usually use previous nesting sites in consecutive years. This gives birds an advantage over younger or invading individuals, as they would already be familiar with the hunting grounds, neighbors, predators, and other features of the site. Males perform elaborate dive displays to advertise their territory and attract a mate. These displays consist of several climbs and dives, with three or four "klee" calls at their peaks. Females are promiscuous for about one to two weeks after their arrival at the nesting site. This is thought to stimulate ovulation. Food transfers from the male to the female occur from about four to five weeks prior to egg laying to one to two weeks after. American kestrels are cavity nesters, but they are able to adapt to a wide variety of nesting situations. They generally prefer natural cavities (such as in trees) with closed tops and tight-fitting entrances that provide for maximum protection of the eggs and young. Kestrels occasionally nest in holes created by large
woodpecker Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions ...
s, or use the abandoned nests of other birds, such as
red-tailed hawk The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members wit ...
s,
merlin Merlin ( cy, Myrddin, kw, Marzhin, br, Merzhin) is a mythical figure prominently featured in the legend of King Arthur and best known as a mage, with several other main roles. His usual depiction, based on an amalgamation of historic and leg ...
s, and crows. They have been recorded nesting on cliff ledges and building tops, as well as in abandoned cavities in
cactus A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gree ...
es. American kestrels also commonly utilize nesting boxes. Three to seven eggs (typically four or five) are laid approximately 24–72 hours apart. (Two supernormal clutches of eight eggs and one of nine have been documented. One egg in one of the eight-egg clutches hatched as did one egg in the nine-egg clutch.) The average egg size is , 10% larger than average for birds of its body size. The eggs are white to cream in color with brown or grey splotching. Incubation usually lasts 30 days and is mainly the responsibility of the female, although the male incubates 15–20% of the time. Eggs that are lost are typically replaced in 11–12 days. Hatching takes place over three to four days. Hatchlings are
altricial In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...
, and are only able to sit up after five days. They grow rapidly, reaching an adult weight after 16–17 days. After 28–31 days, their wings have developed and they are able to leave the nest. The young adult kestrels may breed from a year old, and the species has approximately a three to five-year life expectancy in the wild. In ecological terms, the reproductive pattern of the American kestrel leans towards a small bird "''r'' selection" strategy. In ''r''/''K'' selection theory, selective pressures are hypothesized to drive
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
in one of two generalized directions: ''r'' or ''K'' selection. ''R''-selected species are those that place an emphasis on a high growth rate, typically exploiting less-crowded
ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...
s, and produce many
offspring In biology, offspring are the young creation of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more general way. This ca ...
, each of which has a relatively low probability of surviving to adulthood (i.e., high ''r'', low ''K''). By contrast, ''K''-selected species display traits associated with living at densities close to carrying capacity, and typically are strong competitors in such crowded niches that invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood (i.e., low ''r'', high ''K''). Between these two extremes, the American kestrel is one of the few raptor species that lean towards being ''r''-selected. They are able to breed at one year old, have few non-breeding adults in the population, and have larger broods. Their population growth rate is high relative to larger raptors, which typically lean towards being ''K''-selected.


Stress physiology


Weather

American kestrels are often useful in scientific studies on animal physiology, and are typically captured using the bal-chatri method or raised in nest boxes for experiments. Kestrel metabolic rate has been found to increase in response to rainfall, and at ambient temperatures below about 25 °C. Kestrel metabolic responses to weather and temperature do not vary, however, with sex. Kestrels will increase their oxygen consumption, and therefore their metabolic rate in cold and wet conditions to counteract heat loss.


Environmental disturbance

American kestrels' response to environmental stress is measured as blood concentration of corticosterone (CORT,) a hormone produced by the hypothalamic-pituitary-adrenal (HPA) axis that releases stored energy for essential body functions. Extended periods of elevated blood CORT levels may direct metabolic energy away from growth and reproduction. Thus, high levels of traffic disturbance and human development surrounding American kestrel nests are found to increase stress hormones leading to reproductive failure. Among successful nests, however, nestlings do not typically experience a higher stress response to environmental human disturbance, suggesting that they can tolerate a considerable degree of human activity near the nest.


Environmental contaminants

Since American kestrels are carnivores, toxic chemical runoff ingested by their prey can concentrate at high levels in their blood. Wild kestrels are subject to
immunomodulation Immunomodulation is modulation (regulatory adjustment) of the immune system. It has natural and human-induced forms, and thus the word can refer to the following: * Homeostasis in the immune system, whereby the system self-regulates to adjust immun ...
, or an altered immune response, to polybrominated diphenyl ethers (PBDEs), a group of industrial flame retardants that may leach from factories into the environment. When PBDEs accumulate in body tissues of kestrels, the T-cell mediated immune response decreases in efficiency. As a result, kestrels that ingest PBDEs may not respond sufficiently to viruses or other invading microorganisms. In addition, certain PBDEs may suppress the growth and development of the spleen and bursa in American kestrels. While PBDEs can affect immune response and suppress growth of certain organs, they can also affect the thyroid system of American Kestrels. Exposure to PBDEs ''in vivo'' can alter the thyroid system and retinol concentrations in kestrels. This leads to oxidative stress, lipid peroxidation, and changes in glutathione metabolism. These systems are important in early development, growth, regulation of metabolism, thermoregulation, and reproduction. Oxidative stress is also known to contribute to cancers and neurological diseases. Exposure to PCBs might also affect American Kestrel reproduction. It was found that PCBs affect the function of carotenoids in kestrels. This led to changes in coloration, especially during breeding season for adults. PCB-exposed males where duller and contributed less to egg incubation than unexposed males. PCB-exposed females kept their color longer than they should have. Normally, loss in color is associated with carotenoids being directed to ovaries to help in egg development. PCB-exposed females retained their colors longer, suggesting the PCBs made them less prepared for reproduction. The same females also had significant delays in egg laying. Offspring also showed higher incidence of developmental problems and decreased reproductive success. PCBs have also been found to affect eye color in American Kestrels. Eye color in kestrels is known to vary with age and sex, however, when exposed to PCBs, color patterns were suppressed regardless of age and sex. While it is unknown what role eye color plays in visual acuity, this maybe be of greater concern to birds like kestrels who rely heavily on vision for hunting. PDBEs were linked to changes in breeding behavior in kestrels as well. Different levels of PDBE exposure were linked to different changes in behavior as well. Overall, PDBE exposure led to changes in behaviors that strengthen the bond between a breeding pair. Such behaviors include frequent copulation, food transfers, male posturing, nest box inspection, and specific mating calls (7). High exposure levels led to increases in some behaviors and decreases in some, whereas low exposure caused decreases in almost all behaviors observed. PDBE exposure also altered the timing of these behaviors, often delaying them by several days when compared to the control group. American Kestrels have also been used extensively in toxicology research. Fenthion is a common pesticide that is used to kill insects such as flies and gnats. It was also found that kestrels are highly susceptible to secondary fenthion poisoning. When 14 kestrels were presented with live sparrows who had come into contact with a fenthion solution, all 14 died within 3 days after consuming the sparrows. Diphacinone is another common pesticide that is often used to kill rodents and is thought to be related to secondary poisoning in birds of prey. When kestrels were orally dosed with diphacinone, blood clotting rates significantly decreases. Kestrels were also found to be 20 to 30 times more sensitive to secondary poisoning from diphacinone than other birds like Northern bobwhite and mallard ducks. American kestrels can also be significantly influenced by air contaminants. When exposed to common gaseous pollutants such as benzene, toluene, nitrogen dioxide, and sulfur dioxide, significant changes to the thyroid systems were observed. Higher levels of thyroid activity indicate that exposure to these gases leads to a loss of inhibition of thyroid glands in kestrels. However, there were no changes to immune function or food consumption.


Status and conservation

The American kestrel is likely the most abundant falcon in North America, although its total population is difficult to quantify, as local populations can change quickly due to resource availability. Count data from the USGS Breeding Bird Survey (BBS) indicate that the North American breeding population is experiencing long-term and gradual but sustained declines, with some regions, such as New England and coastal California, exhibiting more rapid declines. Count data from raptor migration corridors also indicate regional population declines and largely corroborate BBS data. The North American population has been estimated at 1.2 million pairs, with the Central and South American populations being as large. A smaller estimate is 236,000 birds wintering in North America. A population increase occurred in the 18th and 19th centuries, probably due to deforestation for agriculture. The resulting pastures provided an ideal habitat for kestrels. The southeastern U.S. subspecies (''Falco sparverius paulus'') has declined 82% since 1940 due to a decrease in nest site availability. This decline is a result of longleaf pines being cleared for agricultural fields. Despite this, the American kestrel is classed as
least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. ...
on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biolo ...
.
The Peregrine Fund The Peregrine Fund (named after the bird of prey of the same name the peregrine falcon) is a non-profit organization founded in 1970 that conserves threatened and endangered birds of prey worldwide. The successful recovery of the peregrine falcon ...
, a leading non-profit organization advancing research and conservation of birds of prey worldwide, launched the American Kestrel Partnership in 2012. The American Kestrel Partnership developed and maintains a web-based network for citizen and professional scientists to enter, manage, and consolidate data from kestrel nest box monitoring programs in the Western Hemisphere. The database is being used by researchers to model and understand relationships between kestrel nesting parameters (e.g., phenology, occupancy, survival, productivity, and nestling weight and exposure to environmental toxins) and environmental factors, such as land use, landscape composition and configuration, climate conditions (e.g., drought), and point sources of environmental toxins. Each breeding season, the American Kestrel Partnership features a live-streaming video feed from the nest box located at The Peregrine Fund's campus in Boise, Idaho.


Use in falconry

One important use of American kestrels is in
falconry Falconry is the hunting of wild animals in their natural state and habitat by means of a trained bird of prey. Small animals are hunted; squirrels and rabbits often fall prey to these birds. Two traditional terms are used to describe a person ...
. It is often considered a beginner's bird, though the careful weight control needed to maintain the kestrel's desire to aggressively hunt takes skill. Falconers experienced in extracting the best performance the species is capable of, report they are highly reliable on the normal game of sparrows and starlings. More aggressive individuals are sometimes capable of capturing prey up to approximately twice their own body weight, allowing the occasional capture of true game birds such as quail and dove. However, most falconers interested in the reliable taking of such game do prefer larger falcons or hawks. The advantage the American kestrel offers the experienced falconer is its suitability to simple and urban falconry not requiring large tracts of land or the use of hunting dogs. This form of falconry is sometimes referred to as "micro-falconry" or "micro-hawking." The other small raptor species commonly used in micro-falconry are the
merlin Merlin ( cy, Myrddin, kw, Marzhin, br, Merzhin) is a mythical figure prominently featured in the legend of King Arthur and best known as a mage, with several other main roles. His usual depiction, based on an amalgamation of historic and leg ...
, the sharp-shinned hawk (the smallest
accipiter ''Accipiter'' is a genus of birds of prey in the family Accipitridae. With 51 recognized species it is the most diverse genus in its family. Most species are called goshawks or sparrowhawks, although almost all New World species (excepting th ...
), and the
European kestrel The common kestrel (''Falco tinnunculus'') is a bird of prey species belonging to the kestrel group of the falcon family Falconidae. It is also known as the European kestrel, Eurasian kestrel, or Old World kestrel. In the United Kingdom, where no ...
(a true kestrel). Hawking with the American kestrel requires adapting to the strengths and weaknesses of the bird. It is a tiny falcon, and even for its size, it is less muscular than other small falcons such as the athletic and swift
merlin Merlin ( cy, Myrddin, kw, Marzhin, br, Merzhin) is a mythical figure prominently featured in the legend of King Arthur and best known as a mage, with several other main roles. His usual depiction, based on an amalgamation of historic and leg ...
. It is more adapted to ambush hunting and short chases than to the longer aerial chases larger falcons often adopt. Used within its limits, it is effective. Experienced falconer Matthew Mullenix, author of the book ''American Kestrels in Modern Falconry'', in an article comparing kestrels to merlins, summed their abilities up as follows: 1. "Kestrels are thin-winged, flat-chested, under-powered and lack acceleration compared to merlins. I say that with much affection for them and with thousands of kestrel kills to prove these are not necessarily damning differences. Comparing a red-tailed hawk to a Harris' or goshawk will conjure equally negative points of fact, yet we all know how good trained red-tails can be!" 2. "The chief variable to choosing between a kestrel and a merlin may be your hawking land. If you live in open country or have access at least to good pasture for cattle, a merlin can excel there. If you plan to hunt mostly in town or suburb, and especially if you plan to hawk from a car, I'd recommend the kestrel. The consideration coming in at close second is your intended quarry. To snipe, dove, quail and open-country sparrows, merlins are best suited. For most blackbirds (Icteridea), either falcon can prove effective. Starlings in close are extremely vulnerable to kestrels, but in the open are best prey for merlins. The same holds true for house sparrows, with this exception: sparrows in thick cover are better quarry for kestrels. This is the slip for which I feel the American kestrel is perfect." 3. "Once committed to an attack, trained kestrels tend to follow through to the end. They will stoop into cover, chase birds on foot, bind to quarry twice their size, and never let go voluntarily. They have small feet, but as written elsewhere, also have the strongest feet for their size. It is a simple fact that American kestrels hold starlings better than merlins, on average, and will gladly tackle larger quarry than will any jack (male merlin)." American kestrels do not train so easily as some larger falcons (particularly the
peregrine falcon The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a cosmopolitan bird of prey (raptor) in the family Falconidae. A large, crow-sized falcon, it has a blue-grey bac ...
) in the art of "waiting on" to perform a diving stoop on flushed prey. However, some individual kestrels do master this skill. Falconers sometimes train them to climb to a stooping position with tidbits on kites or balloons that the kestrels learn to climb after. More common hunting techniques are to "slip" them after spotted game from the fist, or to release them from a vehicle window close to spotted quarry. These techniques are more of a natural fit to the kestrel's ambushing methods in the wild. Falconers using the American kestrel should be alert to protect the falcon from larger predators that may attack the kestrel, particularly if it is distracted on the ground with captured prey. Domestic cats and dogs are the greatest threat to attack the falcon on the ground, but the
Cooper's hawk Cooper's hawk (''Accipiter cooperii'') is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus ''Accipiter'', sometimes referred to as true hawks, which are f ...
is well known to boldly attack kestrels. This mid-sized American
accipiter ''Accipiter'' is a genus of birds of prey in the family Accipitridae. With 51 recognized species it is the most diverse genus in its family. Most species are called goshawks or sparrowhawks, although almost all New World species (excepting th ...
has sufficient size and strength to carry the kestrel away, though falconers have reported often being successful in recovering the kestrel unharmed by acting quickly to intimidate the larger hawk into releasing the kestrel. American kestrels are bred in captivity for use in falconry and are among the easier falcons to breed. They are also sufficiently common that "passage" birds in their first year are relatively easy to trap. Wild-caught kestrels "tame down" fairly quickly. They will usually be eating from a falconer's hand the day after capture, be training within a week, and be ready to hunt in three to five weeks. A very tame American kestrel will allow itself to be picked up around the body with one hand while accepting tidbits from the other hand. Such tameness is very useful when checking or treating the bird for injury or illness. Migratory raptors native to the United States are protected by the
Migratory Bird Treaty Act of 1918 The Migratory Bird Treaty Act of 1918 (MBTA), codified at (although §709 is omitted), is a United States federal law, first enacted in 1918 to implement the convention for the protection of migratory birds between the United States and Canada ...
, so American kestrels are illegal to possess without a permit (such as a falconry permit) in the United States, Canada, and Mexico.


References


Cited books

* *


External links


American Kestrel Partnership, The Peregrine Fund
Research and conservation activities designed for participants of all ages *
KestrelCams, American Kestrel Partnership, The Peregrine Fund
Live, streaming video of a nesting kestrel pair
Photos, audio and video of American kestrel
from
Cornell Lab of Ornithology The Cornell Lab of Ornithology is a member-supported unit of Cornell University in Ithaca, New York, which studies birds and other wildlife. It is housed in the Imogene Powers Johnson Center for Birds and Biodiversity in Sapsucker Woods Sanctuar ...
's Macaulay Library *
American Kestrel – ''Falco sparverius''
– USGS Patuxent Bird Identification InfoCenter * {{Taxonbar , from=Q651545 American kestrel Birds of the Americas Birds of the Dominican Republic American kestrel American kestrel