Its breeding range extends from central and western Alaska across
northern Canada to Nova Scotia, and south throughout North America, into central
Mexico and 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.
The American kestrel is the smallest falcon in North America and, under
traditional classification, 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 12 to 27 cm (4.7 to 10.6 in)
in length with a wingspan of 50–61 cm (20–24 in). The female kestrel is larger
than the male. The male weighs 80–105 g (2.8–3.7 oz), as opposed to the female
which weighs 100–120 g (3.5–4.2 oz). In standard measurements, the wing bone is
16–21 cm (6.3–8.3 in) long, the tail is 11–15 cm (4.3–5.9 in) and the tarsus is
3.2–4 cm (1.3–1.6 in).
In contrast to many other raptor species, the sexes differ more in plumage
than in size. Males have blue-grey wings with black spots and white undersides
with black barring. The back is rufous, 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. The wings are moderately long, fairly narrow,
and taper to a point.
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. The "chitter" is used in activities which involve
interaction between male and female birds, including courtship feeding,
copulation, and the feeding of nestlings. Nestlings can produce calls similar to
those of adults at 16 days old.
Until the sixth edition of the AOU Checklist of North American Birds was
published by the American Ornithologists' Union in 1983, the most commonly used
name for the American kestrel was the sparrow hawk or sparrowhawk. This was due
to a mistaken connection with the Eurasian sparrowhawk in the genus Accipiter.
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
The American kestrel's scientific name, Falco sparverius, was given by
Carolus Linnaeus in his 18th century work Systema Naturae. 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 occasional
hunting of sparrows.
American kestrels are found in a wide variety of habitats, including
grasslands, meadows, deserts, and other open to semiopen 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 4,500 m (14,800 ft) in the Andes Mountains. The bird is
distributed from northern Canada and Alaska to the southernmost tip of South
America, Tierra del Fuego. It is the only kestrel found in the Americas. It has
occurred as a vagrant in the UK, Denmark, Malta and the Azores.
American kestrels in Canada and the northern United States typically
migrate south in the winter, 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.
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 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.
American kestrels feed largely on small animals such as grasshoppers,
dragonflies, lizards, mice, and voles. They will occasionally eat small birds.
The kestrel has also been reported to have killed snakes, bats, and squirrels.
The estrel 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 lines, 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
Prey is almost always caught on the ground. Before striking, the kestrel
characteristically bobs its head and tail, then makes a direct flight toward the
prey to grab it in its talons. 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
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, as to provide for
maximum protection of the eggs and young. Kestrels occasionally nest in holes
created by large woodpeckers, or use the abandoned nests of other birds, such as
red-tailed hawks, merlins, andcrows.[They have been recorded nesting on cliff
ledges and building tops, as well as in abandoned cavities in cactuses. American
kestrels also commonly utilize nesting boxes.
Three to seven eggs (typically four or five) are laid approximately 24–72
hours apart. The average egg size is 32 mm × 29 mm (1.3 in × 1.1 in), 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 which are lost are typically replaced in 11–12 days. Hatching takes
place over three to four days. Hatchlings are altricial, and are only able to
sit up after five days. They grow very quickly, reaching an adult weight after
16–17 days. After 28–31 days, their wings develop and they are able to leave the
nest. The young adults kestrels may breed from a year old, and the species
has a ten year life expectancy.
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.
One important use of American kestrels is in falconry. It is definitely not
a beginner's bird, due to the careful weight control needed to maintain the
kestrel's flying weight without killing it by either over or underfeeding. This
is made problematic by their small size. 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, particularly in ambushing this prey
by surprise when released out of a vehicle window. 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.