American kestrel

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American kestrel
AmericanKestrel02.jpg
Male
Female American Kestrel.jpg
Female at the Cincinnati Zoo
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Falconiformes
Family: Falconidae
Genus: Falco
Species:
F. sparverius
Binomial name
Falco sparverius
Falco sparverius range map.svg
American kestrel range
  Year round
  Summer (breeding)
  Winter (nonbreeding)
Adult female in Winnipeg, Manitoba, Canada Bluekestrel1a.jpg
Adult female in Winnipeg, Manitoba, Canada
Kestrel resting in an apple tree. American Kestrel, Colorado.jpg
Kestrel resting in an apple tree.

The American kestrel (Falco sparverius), is the smallest and most common falcon in North America. Formerly called "sparrowhawk", a misnomer as it is a true falcon and is unrelated genetically to the Eurasian sparrowhawk, Accipiter nisus .[ citation needed ] 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 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 in size (females being moderately larger) and plumage, although both sexes have a rufous back with noticeable barring. Its plumage is colorful and attractive, and juveniles are similar in plumage to adults.

Contents

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 grasshoppers and other insects, lizards, mice, and small birds (e.g. sparrows). 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 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.

Based on appearance and behavior it was for many years considered a member of the primarily European and African kestrel clade 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 peregrine, [2] aplomado, and prairie falcons. [3] Though the species has not been renamed as a result of these genetic analyses, it is not actually a kestrel in the phylogenetic sense. Instead, a process of convergent evolution 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, 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. [4]

Description

Under traditional classification, the American kestrel is the smallest raptor in America. [5] The American kestrel is sexually dimorphic, although there is some overlap in plumage coloration between the sexes. The bird ranges from 22 to 31 cm (8.7 to 12.2 in) in length [6] with a wingspan of 51–61 cm (20–24 in). 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 80–143 g (2.8–5.0 oz), and the female 86–165 g (3.0–5.8 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). [7] [8] [9]

Physically, American kestrels are leaner and less muscular than larger falcons. [10] 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. [11] 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 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. [12] 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'. [12] 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. [13] Two black spots (ocelli) can be found on each side of the white or orangish nape. [14] 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. [15]

Vocalizations

The American kestrel has three basic vocalizations – the "klee" or "killy", the "whine", and the "chitter". [16] 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 that involve interaction between male and female birds, including courtship feeding, copulation, and the feeding of nestlings. [17] Nestlings can produce calls similar to those of adults at 16 days old. [18]

Taxonomy

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. 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 distinct call. [19]

As noted in the introduction, DNA analysis shows the American kestrel to actually be genetically more closely related to the larger American falcons [2] [3] 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 in his 18th century work Systema Naturae . [20] 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. [19]

Seventeen subspecies of the American kestrel are recognized, generally based upon plumage, size, and vocalizations: [21]

Ecology and behavior

American kestrels are found in a wide variety of habitats, including grasslands, meadows, deserts 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). [22] The American kestrel is able to live in very diverse conditions, ranging from above the Arctic Circle, [23] to the tropics of Central America, to elevations of over 4,500 m (14,800 ft) in the Andes Mountains. [24] 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, [25] though as mentioned above this classification is genetically inaccurate. It has occurred as a vagrant in the UK, Denmark, Malta and the Azores. [26]

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, [27] [28] 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. [29] 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. [30] 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. [31]

The American kestrel is not long-lived, with a lifespan of <5 years for wild birds. [32] The oldest banded wild bird was 11 years and 7 months, [33] while captive kestrels can live up to 14–17 years. [32] 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. [32]

Feeding

American kestrels feed largely on small animals such as grasshoppers, [34] crickets, butterflies, moths, [35] dragonflies, beetles, [36] lizards, mice, voles, shrews, frogs, [35] and small birds. The kestrel has also been reported to have killed scorpions, snakes, [37] bats, [38] and squirrels. [39] 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 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 air. [40]

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, American kestrels conserve energy in a hunt and pick their attacks with care as to position and odds of success. [10] 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. [41]

Reproduction

Falco sparverius - MHNT Falco sparverius MHNT.ZOO.2010.11.104.1.jpg
Falco sparverius - MHNT
A young bird Young American Kestrel.jpeg
A young bird

American kestrels are sexually mature by their first spring. [42] 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. [43] 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. [44] 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. [45]

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. [46] Kestrels occasionally nest in holes created by large woodpeckers, [47] or use the abandoned nests of other birds, such as red-tailed hawks, merlins, and crows. [48] They have been recorded nesting on cliff ledges and building tops, as well as in abandoned cavities in cactuses. [49] [37] American kestrels also commonly utilize nesting boxes. [50]

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.) [51] 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 that 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 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. [52] 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. [53] In r/K selection theory, selective pressures are hypothesized to drive evolution in one of two generalized directions: r or K selection. [54] R-selected species are those that place an emphasis on a high growth rate, typically exploiting less-crowded ecological niches, and produce many offspring, 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. [55] 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. [56] Kestrels will increase their oxygen consumption, and therefore their metabolic rate in cold and wet conditions to counteract heat loss. [56] [57]

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. [55] Thus, high levels of traffic disturbance and human development surrounding American kestrel nests are found to increase stress hormones leading to reproductive failure. [58] 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. [55]

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, 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. [59]

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. [60] 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. [61]

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. [62] 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. [62]

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. [63] While it is unknown what role eye color plays in visual acuity, this may 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. [64]

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. [65] 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. [66]

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. [67] 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. [68] However, there were no changes to immune function or food consumption.

Status and conservation

A rehabilitated male American kestrel with handler at an educational event. American kestrel (44273).jpg
A rehabilitated male American kestrel with handler at an educational event.

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. [69] [70] Count data from raptor migration corridors also indicate regional population declines and largely corroborate BBS data. [71] 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. [32]

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. [72] Despite this, the American kestrel is classed as least concern on the IUCN Red List. [1]

The Peregrine Fund, a leading non-profit organization advancing research and conservation of birds of prey worldwide, launched the American Kestrel Partnership in 2012. [73] 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 [74] from the nest box located at The Peregrine Fund's campus in Boise, Idaho. [73]

Use in falconry

Male with handler, San Diego Zoo San Diego City College Zoo booth at Earth Day 2007.JPG
Male with handler, San Diego Zoo

One important use of American kestrels is in falconry. 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. [75] 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" [76] or "micro-hawking". The other small raptor species commonly used in micro-falconry are the merlin, the sharp-shinned hawk (the smallest accipiter), and the European kestrel (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. 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, [10] 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) in the art of "waiting on" to perform a diving stoop on flushed prey. However, some individual kestrels do master this skill. [77] 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 is well known to boldly attack kestrels. This mid-sized American accipiter 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. [78]

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. [79] 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, so American kestrels are illegal to possess without a permit (such as a falconry permit) in the United States, Canada, and Mexico. [80]

Related Research Articles

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<span class="mw-page-title-main">Merlin (bird)</span> Species of bird

The merlin is a small species of falcon from the Northern Hemisphere, with numerous subspecies throughout North America and Eurasia. A bird of prey once known colloquially as a pigeon hawk in North America, the merlin breeds in the northern Holarctic; some migrate to subtropical and northern tropical regions in winter. Males typically have wingspans of 53–58 centimetres (21–23 in), with females being slightly larger. They are swift fliers and skilled hunters which specialize in preying on small birds in the size range of sparrows to quail. The merlin has for centuries been well regarded as a falconry bird. In recent decades merlin populations in North America have been significantly increasing, with some merlins becoming so well adapted to city life that they forgo migration.

<span class="mw-page-title-main">Eurasian sparrowhawk</span> Species of bird

The Eurasian sparrowhawk, 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-barred underparts; females and juveniles are brown above with brown barring below. The female is up to 25% larger than the male – one of the greatest size differences between the sexes in any bird species. Though it is a predator which specialises in catching woodland birds, the Eurasian sparrowhawk can be found in any habitat and often hunts garden birds in towns and cities. Males tend to take smaller birds, including tits, finches, and sparrows; females catch primarily thrushes and starlings, but are capable of killing birds weighing 500 g (18 oz) or more.

<span class="mw-page-title-main">Rough-legged buzzard</span> Species of bird

The rough-legged buzzard (Europe) or rough-legged hawk is a medium-large bird of prey. It is found in Arctic and Subarctic regions of North America, Europe, and Russia during the breeding season and migrates south for the winter. It was traditionally also known as the rough-legged falcon in such works as John James Audubon's The Birds of America.

<span class="mw-page-title-main">Nankeen kestrel</span> Species of bird

The nankeen kestrel, also known as the Australian kestrel, is a raptor native to Australia and New Guinea. It is one of the smallest falcons, and unlike many, does not rely on speed to catch its prey. Instead, it simply perches in an exposed position, but it also has a distinctive technique of hovering over crop and grasslands.

<span class="mw-page-title-main">Red-necked falcon</span> Species of bird

The red-necked falcon is a bird of prey in the falcon family with two disjunct populations, one in India and the other in Africa. This medium-sized falcon has bluish grey wings and upper body, a chestnut red cap with short chin straps passing through the eye. The primary feathers of the wing are black and a single black band at the tip of the tail are distinctive. The Indian subspecies Falco chicquera chicquera also known as the red-headed merlin or red-headed falcon is found mainly in the open plains of the India Subcontinent although it is thought to have occurred further west in southeastern Iran. The subspecies Falco chicquera ruficollis found in sub-Saharan Africa is sometimes treated as a full species, the rufous-necked falcon, on the basis of its well-separated geographic range and distinctive pattern. It appears very similar to the Indian form but has dark barring on the upperparts, a rufous breast band, and black moustachial and eye stripes. As in most falcons, the females are larger and falconers in India called the female turumti and the male as chatwa. They hunt in pairs mostly at dawn and dusk, capturing small birds, bats and squirrels.

<span class="mw-page-title-main">Harris's hawk</span> Species of bird

Harris's hawk, formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south to Chile, central Argentina, and Brazil. This bird is sometimes reported to be at large in Western Europe, especially Britain, but it is a popular species in falconry and these records almost invariably all refer to escapes from captivity.

<span class="mw-page-title-main">Lanner falcon</span> Bird of prey

The lanner falcon is a medium-sized bird of prey that breeds in Africa, southeast Europe and just into Asia. It prefers open habitat and is mainly resident, but some birds disperse more widely after the breeding season. A large falcon, it preys on birds and bats. Most likely either the lanner or peregrine falcon was the sacred species of falcon to the ancient Egyptians, and some ancient Egyptian deities, like Ra and Horus, were often represented as a man with the head of a lanner falcon.

<span class="mw-page-title-main">Saker falcon</span> Species of bird

The saker falcon is a large falcon species. It breeds from Central Europe eastwards across the Palearctic to Manchuria. It is a partial migrant, which means that some part of the population is migratory, some part is not. In Europe, for example, a part of the juveniles are migrating, while adults are mostly resident. The European and West Asian migratory sakers spend the winter in the Sahel region. On migration, they cross the Middle East, the Arabian peninsula, and Pakistan, where they are exposed to illegal trapping. The migratory birds to the east from Altai Mountains spend the winter in the Qinghai-Tibet Plateau.

<span class="mw-page-title-main">Prairie falcon</span> Species of bird

The prairie falcon 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 in), and average weight of 720 g (1.6 lb). As in all falcons, females are noticeably bigger than males. Though a separate species from the peregrine, the prairie falcon is basically an arid environment divergence of the early peregrine falcon lineage, able to subsist on less food than the peregrine, and generally lighter in weight than a peregrine of similar wing span. Having evolved in a harsh desert environment with low prey density, the prairie falcon has developed into an aggressive and opportunistic hunter of a wide range of both mammal and bird prey. It will regularly take prey from the size of sparrows to approximately its own weight, and occasionally much larger. It is the only larger falcon native only to North America. It is resident from southern Canada, through western United States, and into northern Mexico. The prairie falcon is popular as a falconry bird, where with proper training it is regarded as being as effective as the more well known peregrine falcon.

<span class="mw-page-title-main">Aplomado falcon</span> Species of bird

The aplomado falcon is a medium-sized falcon of the Americas. The species' largest continuous range is in South America, but not in the deep interior Amazon Basin. It was long known as Falco fusco-coerulescens or Falco fuscocaerulescens, but these names are now believed to refer to the bat falcon. Its resemblance in shape to the hobbies accounts for its old name orange-chested hobby. Aplomado is an unusual Spanish word for "lead-colored", referring to the blue-grey areas of the plumage – an approximate English translation would be "plumbeous falcon". Spanish names for the species include halcón aplomado and halcón fajado ; in Brazil it is known as falcão-de-coleira.

<span class="mw-page-title-main">Australian hobby</span> Species of bird

The Australian hobby, also known as the little falcon, is one of six Australian members of the family Falconidae. This predominantly diurnal bird of prey derives its name ‘longipennis’ from its long primary wing feathers. It occurs throughout Australia and other neighbouring countries with migrating individuals found on the islands of Indonesia and New Guinea.

<span class="mw-page-title-main">Spotted kestrel</span> Species of bird

The spotted kestrel is also known as the Moluccan kestrel.

<span class="mw-page-title-main">Gyrfalcon</span> Species of bird

The gyrfalcon, the largest of the falcon species, is a bird of prey. The abbreviation gyr is also used. It breeds on Arctic coasts and tundra, and the islands of northern North America and the Eurosiberian region. It is mainly a resident there also, but some gyrfalcons disperse more widely after the breeding season, or in winter. Individual vagrancy can take birds for long distances. Its plumage varies with location, with birds being coloured from all-white to dark brown. These colour variations are called morphs. Like other falcons, it shows sexual dimorphism, with the female much larger than the male. For centuries, the gyrfalcon has been valued as a hunting bird. Typical prey includes the ptarmigan and waterfowl, which it may take in flight; it also takes fish and mammals.

<span class="mw-page-title-main">Eurasian goshawk</span> Species of bird

The Eurasian goshawk is a species of medium-large bird of prey in the family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harriers. As a species in the genus Accipiter, the goshawk is often considered a "true hawk". The scientific name is Latin; Accipiter is "hawk", from accipere, "to grasp", and gentilis is "noble" or "gentle" because in the Middle Ages only the nobility were permitted to fly goshawks for falconry.

References

  1. 1 2 BirdLife International (2016). "Falco sparverius". IUCN Red List of Threatened Species . 2016: e.T22696395A93559037. doi: 10.2305/IUCN.UK.2016-3.RLTS.T22696395A93559037.en . Retrieved 19 February 2022.
  2. 1 2 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.
  3. 1 2 Griffiths, C. (1999). "Phylogeny of the Falconidae Inferred from Molecular and Morphological Data". The Auk. 116 (1): 116–130. doi: 10.2307/4089459 . JSTOR   4089459.
  4. Mullenix
  5. Wauer
  6. Davis, Kate, Falcons of North America, 2008, Mountain Press Publishing Company, ISBN   978-0-87842-553-2, Kindle Edition, Location 2232.
  7. McCollough, Kathryn (2001). "American Kestrel Falco sparverius". Animal Diversity Web. University of Michigan Museum of Geology. Archived from the original on 13 September 2010. Retrieved 13 September 2010.
  8. Ferguson-Lees, James; Christie, David A. (2001). Raptors of the World. Houghton Mifflin. ISBN   978-0-618-12762-7.
  9. American Kestrel, Life History, All About Birds – Cornell Lab of Ornithology. Allaboutbirds.org. Retrieved 2013-02-25.
  10. 1 2 3 Mullenix, Matt (2003) Merlins and American Kestrels Compared. merlinfalconry.com.
  11. Davis, Kate, Kindle locations 225–234.
  12. 1 2 "American Kestrel, Falco sparverius". Cornell Lab of Ornithology. Retrieved 13 September 2010.
  13. Tveten, John L.; Tveten, Gloria A. (2004). "Our Smallest Falcon—American Kestrel: 198/1996". Our life with birds: a nature trails book. College Station, TX: Texas A&M University Press. p. 210. ISBN   978-1-58544-380-2.
  14. Clark, William S.; Wheeler, Brian K. (2001). A field guide to hawks of North America. New York, NY: Houghton Mifflin Harcourt. p. 252. ISBN   978-0-395-67067-5.
  15. Negro, Juan José; Bortolotti, Gary R.; Sarasola, José Hernán (2007). "Deceptive plumage signals in birds: manipulation of predators or prey?". Biological Journal of the Linnean Society. 90 (3): 467–477. doi: 10.1111/j.1095-8312.2007.00735.x . hdl: 10261/33914 .
  16. Mueller, Helmut C. (1971). "Displays and Vocalizations of the Sparrow Hawk". The Wilson Bulletin. 83 (3): 249–254. JSTOR   4160099.
  17. Wauer, pp. 11–12
  18. Smallwoood, John A.; Dudajek, Valerie (2003). "Vocal Development in American Kestrel (Falco sparverius) Nestlings". Journal of Raptor Research. 37 (1): 37–43.
  19. 1 2 Wauer, p. 4
  20. Linnaeus, Carolus (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata (in Latin). Holmiae: Laurentii Salvii. p. 152.
  21. Smallwood, John A.; Bird, David M. (2002). "American Kestrel: Systematics". Cornell Lab of Ornithology. Retrieved 4 September 2010.
  22. "American Kestrel, Life History". All About Birds. Cornell Lab of Ornithology. Retrieved 3 September 2010.
  23. Wauer, p. 15
  24. Fjeldså, Jon; Krabbe, Niels (1990). Birds of the High Andes: A Manual to the Birds of the Temperate Zone of the Andes and Patagonia, South America. Svendborg, Denmark: Apollo Books. p. 112. ISBN   978-87-88757-16-3.
  25. Smallwood, John A.; Bird, David M. (2002). "American Kestrel: Introduction". Cornell Lab of Ornithology. Archived from the original on 26 September 2010. Retrieved 2 November 2010.
  26. Snow, David (1998). Perrins, Christopher M (ed.). The Birds of the Western Palearctic concise edition. Oxford: Oxford University Press. p. 152. ISBN   978-0-19-850188-6.
  27. Frixione, Martín G.; Rodríguez-Estrella, Ricardo (1 December 2020). "Genotoxicity in American kestrels in an agricultural landscape in the Baja California peninsula, Mexico". Environmental Science and Pollution Research. 27 (36): 45755–45766. doi:10.1007/s11356-020-10392-0. ISSN   1614-7499. PMID   32803597. S2CID   221132575.
  28. "The Journal of Raptor Research". meridian.allenpress.com. Retrieved 22 September 2023.
  29. Wauer, pp. 23–24
  30. Powers, Breanna F.; Winiarski, Jason M.; Requena‐Mullor, Juan M.; Heath, Julie A. (October 2021). "Intra‐specific variation in migration phenology of American Kestrels ( Falco sparverius ) in response to spring temperatures". Ibis. 163 (4): 1448–1456. doi:10.1111/ibi.12953. ISSN   0019-1019. S2CID   233642891.
  31. Ardia, Daniel R.; Bildstein, Keith L. (1997). "Sex-related differences in habitat selection in wintering American kestrels, Falco sparverius". Animal Behaviour. 53 (6): 1305–1311. CiteSeerX   10.1.1.597.3819 . doi:10.1006/anbe.1996.0364. PMID   9236026. S2CID   20672015.
  32. 1 2 3 4 Smallwood, John A.; Bird, David M. (2002). "American Kestrel: Demography and Populations". Cornell Lab of Ornithology. Retrieved 27 May 2012.
  33. Clapp, Roger B.; Klimkiewicz, M. Kathleen; Kennard, John H. (1982). "Longevity Records of North American Birds: Gaviidae through Alcidae". Journal of Field Ornithology. 53 (2): 81–124. JSTOR   4512701.
  34. Orozco-Valor, Paula M.; Grande, Juan M. (20 August 2021). "Diet Variation of a Generalist Predator, the American Kestrel Falco sparverius, in a Gradient of Agricultural Intensification in Central Argentina". Acta Ornithologica. 56 (1). doi:10.3161/00016454AO2021.56.1.008. ISSN   0001-6454. S2CID   237247221.
  35. 1 2 Townes, Sutton. "Falco sparverius (American kestrel)". Animaldiversity.org. Retrieved 16 March 2022.
  36. "American kestrel (Falco sparverius)" (PDF). Sta.wi.edu. Retrieved 16 March 2022.
  37. 1 2 Frixione, Martín G.; Rodríguez-Estrella, Ricardo (1 November 2020). "Trophic segregation of the Burrowing Owl and the American Kestrel in fragmented desert in Mexico". Journal of Natural History. 54 (41–42): 2713–2732. doi:10.1080/00222933.2020.1865470. ISSN   0022-2933. S2CID   234998691.
  38. Mikula, P.; Morelli, F.; Lučan, R. K.; Jones, D. N.; Tryjanowski, P. (2016). "Bats as prey of diurnal birds: a global perspective". Mammal Review. 46 (3): 160. doi:10.1111/mam.12060.
  39. Sherrod, Steve K. (1978). "Diets of North American Falconiformes". Journal of Raptor Research. 12 (2): 103–106.
  40. Collopy, Michael W.; Koplin, James R. (1983). "Diet, Capture Success, and Mode of Hunting by Female American Kestrels in Winter". The Condor. 85 (3): 369–371. doi:10.2307/1367081. JSTOR   136708.
  41. Rudolph, Seri G. (1982). "Foraging Strategies of American Kestrels During Breeding". Ecology. 63 (5): 1268–1276. doi:10.2307/1938854. JSTOR   1938854.
  42. Duncan, James, R.; Bird, David M. (1989). "The influence of relatedness and display effort on the mate choice of captive female American kestrels" (PDF). Animal Behaviour. 37: 112–117. doi:10.1016/0003-3472(89)90011-0. hdl: 2027.42/28134 . S2CID   4537910.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  43. Wauer, p. 52
  44. Wauer, p. 54
  45. Smallwood, John A.; Bird, David M. (2002). "American Kestrel: Behavior". Cornell Lab of Ornithology. Retrieved 25 September 2010.
  46. Wauer, p. 55
  47. Gault, Kathleen E.; Walters, Jeffrey R.; Tomcho, Joseph Jr.; Phillips, Louis F. Jr.; Butler, Andrew (2004). "Nest Success of Southeastern American Kestrels Associated with Red-Cockaded Woodpeckers in Old-Growth Longleaf Pine Habitat in Northwest Florida". Southeastern Naturalist. 3 (2): 191–204. doi:10.1656/1528-7092(2004)003[0191:NSOSAK]2.0.CO;2. JSTOR   3878098. S2CID   56436619.
  48. Wauer, pp. 55–56
  49. Smith, Dwight G.; Wilson, Charles R.; Frost, Herbert H. (1972). "The Biology of the American Kestrel in Central Utah". The Southwestern Naturalist. 17 (1): 73–83. doi:10.2307/3669841. JSTOR   3669841.
  50. Rohrbaugh, Ronald W. Jr.; Yahner, Richard H. (1997). "Effects of Macrohabitat and Microhabitat on Nest-Box Use and Nesting Success of American Kestrels". The Wilson Bulletin. 109 (3): 410–423. JSTOR   4163837.
  51. Miller, Karl E. (2020). "Supernormal clutches of American Kestrels (Falco sparverius) in peninsular Florida". The Wilson Journal of Ornithology. 132 (2): 438–441.
  52. Wauer, pp. 59–63
  53. Davis, Kate, Kindle location 948.
  54. Pianka, E.R. (1970). "On r and K selection". American Naturalist. 104 (940): 592–597. doi:10.1086/282697. S2CID   83933177.
  55. 1 2 3 Strasser, Erin H.; Heath, Julie A. (2011). "Effects of developmental conditions on nestling American Kestrel (Falco sparverius) corticosterone concentrations". General and Comparative Endocrinology. 173 (1): 164–170. doi:10.1016/j.ygcen.2011.05.010. PMID   21641910.
  56. 1 2 Wilson, Glenn R.; Cooper, Sheldon J.; Gessaman, James A. (1 November 2004). "The effects of temperature and artificial rain on the metabolism of American kestrels (Falco sparverius)". Comparative Biochemistry and Physiology A. 139 (3): 389–394. doi:10.1016/j.cbpb.2004.10.009. PMID   15556396.
  57. Willmer, Pat; Stone, Graham; Johnston, Ian (2009). Environmental Physiology of Animals (2nd ed.). Wiley. p. 126. ISBN   9781444309225.
  58. Strasser, Erin H.; Heath, Julie A. (1 August 2013). "Reproductive failure of a human-tolerant species, the American kestrel, is associated with stress and human disturbance". Journal of Applied Ecology. 50 (4): 912–919. doi:10.1111/1365-2664.12103.
  59. Fernie, Kim J.; Mayne, Greg; Shutt, J. Laird; Pekarik, Cynthia; Grasman, Keith A.; Letcher, Robert J.; Drouillard, Ken (1 December 2005). "Evidence of immunomodulation in nestling American kestrels (Falco sparverius) exposed to environmentally relevant PBDEs". Environmental Pollution. 138 (3): 485–493. doi:10.1016/j.envpol.2005.04.008. PMID   15951077.
  60. Fernie, K. J.; Shutt, J. L.; Mayne, G.; Hoffman, D.; Letcher, R. J.; Drouillard, K. G.; Ritchie, I. J. (2005). "Exposure to Polybrominated Diphenyl Ethers (PBDEs): Changes in Thyroid, Vitamin A, Glutathione Homeostasis, and Oxidative Stress in American Kestrels (Falco sparverius)". Toxicological Sciences. 88 (2): 375–383. doi: 10.1093/toxsci/kfi295 . PMID   16120752 . Retrieved 6 March 2022.
  61. Pizzino, Gabriele; Irrera, Natasha; Cucinotta, Mariapaola; Pallio, Giovanni; Mannino, Federica; Arcoraci, Vincenzo; Squadrito, Francesco; Altavilla, Domenica; Bitto, Alessandra (2017). "Oxidative Stress: Harms and Benefits for Human Health". Oxidative Medicine and Cellular Longevity. 2017: 8416763. doi: 10.1155/2017/8416763 . ISSN   1942-0900. PMC   5551541 . PMID   28819546.
  62. 1 2 Bortolotti, Gary R.; Fernie, Kimberly J.; Smits, Judit E. (2003). "Carotenoid Concentration and Coloration of American Kestrels (Falco sparverius) Disrupted by Experimental Exposure to PCBs". Functional Ecology. 17 (5): 651–657. doi:10.1046/j.1365-2435.2003.00778.x. ISSN   0269-8463. JSTOR   3599160.
  63. Bortolotti, GaryR.; Smits, JuditE.; Bird, DavidM. (January 2003). "Iris Colour of American Kestrels Varies with Age, Sex, and Exposure to PCBs". Physiological and Biochemical Zoology. 76 (1): 99–104. doi:10.1086/345485. ISSN   1522-2152. PMID   12695990. S2CID   37168509.
  64. Fernie, Kim J.; Shutt, John L.; Letcher, Robert J.; Ritchie, James I.; Sullivan, Katrina; Bird, David M. (March 2008). "Changes in Reproductive Courtship Behaviors of Adult American Kestrels (Falco sparverius) Exposed to Environmentally Relevant Levels of the Polybrominated Diphenyl Ether Mixture, DE-71". Toxicological Sciences. 102 (1): 171–178. doi:10.1093/toxsci/kfm295.
  65. PubChem. "Fenthion". pubchem.ncbi.nlm.nih.gov. Retrieved 6 March 2022.
  66. Hunt, K. A.; Bird, D. M.; Mineau, P.; Shutt, L. (1 July 1991). "Secondary poisoning hazard of fenthion to American kestrels". Archives of Environmental Contamination and Toxicology. 21 (1): 84–90. doi:10.1007/BF01055561. ISSN   1432-0703. PMID   1898122. S2CID   30935069.
  67. Rattner, Barnett A.; Horak, Katherine E.; Warner, Sarah E.; Day, Daniel D.; Meteyer, Carol U.; Volker, Steven F.; Eisemann, John D.; Johnston, John J. (11 March 2011). "Acute toxicity, histopathology, and coagulopathy in American kestrels (Falco sparverius) following administration of the rodenticide diphacinone". Environmental Toxicology and Chemistry. 30 (5): 1213–1222. doi:10.1002/etc.490. ISSN   0730-7268. PMID   21337606. S2CID   9840733.
  68. Fernie, Kim J.; Cruz-Martinez, Luis; Peters, Lisa; Palace, Vince; Smits, Judit E.G. (18 October 2016). "Inhaling Benzene, Toluene, Nitrogen Dioxide, and Sulfur Dioxide, Disrupts Thyroid Function in Captive American Kestrels (Falco sparverius)". Environmental Science & Technology. 50 (20): 11311–11318. Bibcode:2016EnST...5011311F. doi:10.1021/acs.est.6b03026. ISSN   0013-936X. PMID   27646166.
  69. Sauer, J.R.; Hines, J.E.; Fallon, J.E.; Pardieck, J.L.; Ziolkowski Jr., D.J.; Link, W.A. (2011). "The North American Breeding Bird Survey, Results and Analysis 1966 – 2010. Version 12.07.2011". USGS Patuxent Wildlife Research Center. Archived from the original on 9 June 2012. Retrieved 27 May 2012.
  70. "American Kestrel Partnership: population declines". The Peregrine Fund. 2012. Retrieved 27 May 2012.
  71. "Raptor Population Index, Regional Population Trend Summaries 2011". Raptor Population Index. 2012. Archived from the original on 3 March 2016. Retrieved 27 May 2012.
  72. Hoffman, Mark L.; Collopy, Michael W. (1988). "Historical Status of the American Kestrel (Falco sparverius paulus) in Florida". The Wilson Bulletin. 100 (1): 91–107. JSTOR   4162520.
  73. 1 2 "American Kestrel Partnership". The Peregrine Fund. 2012. Retrieved 27 May 2012.
  74. Live-streaming video feed, The Peregrine Fund
  75. Mullenix, pp. 82–84
  76. Kestrels, Merlins, and Micro-falconry. oregonfalconers.com (2012)
  77. Mullenix, p. 80
  78. Mullenix, p. 107
  79. Mullenix, p. 48
  80. "Legal Requirements for Raptor Possession". Bureau of Land Management. 15 July 2008. Archived from the original on 21 August 2010. Retrieved 29 October 2010.

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