The merlin (Falco columbarius) is a small species of falcon from the Northern Hemisphere,[2] 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 (21–23in), 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.
Nomenclature
The merlin was described and illustrated by the English naturalist Mark Catesby (as the "pigeon hawk") in his Natural history of Carolina, Florida and the Bahama Islands published in 1729–1732.[3][4] Based on this description, in 1758 Carl Linnaeus included the species in the tenth edition of his Systema Naturae and introduced the present binomial nameFalco columbarius with the type locality as "America".[5] The genus name is Late Latin; falco derives from falx, falcis, a sickle, referring to the claws of the bird.[6] The species name columbarius is Latin for "of doves" from "columba", "dove".[7] Thirteen years after Linnaeus's description Marmaduke Tunstall recognized the Eurasian birds as a distinct taxonFalco aesalon in his Ornithologica Britannica. If two species of merlins are recognized, the Old World birds would thus bear the scientific nameF. aesalon.[8][9]
The name "merlin" is derived from Old Frenchesmerillon via Anglo-Normanmerilun or meriliun. There are related Germanic words derived through older forms such as Middle Dutchsmeerle, Old High Germansmerle and Old Icelandicsmyrill.[10]Wycliffe's Bible, around 1382, mentions An Egle, & agriffyn, & a merlyon.[10] The species was once known as 'pigeon hawk' in North America.[11]
Although the merlin's name looks and sounds like the name of the wizard Merlin prominent in Arthurian legend, the bird is not named after the wizard.[12] The wizard's name is an English cognate of the Welsh name "Myrddin" and is unrelated to the name of the bird.
Systematics
The relationships of the merlin are not resolved to satisfaction. In size, shape and coloration, it is fairly distinct among living falcons. The red-necked falcon is sometimes considered more closely related to the merlin than other falcons, but this seems to be a coincidence due to similar hunting habits; it could not be confirmed in more recent studies. Indeed, the merlin seems to represent a lineage distinct from other living falcons since at least the Early Pliocene, some 5 Ma (million years ago). As suggested by biogeography and DNA sequence data, it might be part of an ancient non-monophyleticradiation of Falcos from Europe to North America, alongside the ancestors of forms such as the American kestrel (F. sparvierus), and the aplomado falcon (F. femoralis) and its relatives. A relationship with the red-necked falcon (F. chicquera) was once proposed based on their phenetic similarity, but this is not considered likely today.[8][9][13][14][15]
In that regard, a fossil falcon from the Early Blancan (4.3–4.8 Ma)[16]Rexroad Formation of Kansas. Known from an almost complete right coracoid (specimen UMMP V29107) and some tarsometatarsus, tibiotarsus and humerus pieces (V27159, V57508-V57510, V57513-V57514), this prehistoric falcon was slightly smaller than a merlin and apparently a bit more stout-footed, but otherwise quite similar. It was part of the Fox Canyon and Rexroad Local Faunas, and may have been the ancestor of the living merlins or its close relative. With its age quite certainly pre-dating the split between the Eurasian and North American merlins, the fossil falcon supports the idea of the merlin lineage originating in North America, or rather the colonization thereof. After adapting to its ecological niche, ancient merlins would have spread to Eurasia again, with gene flow being interrupted as the Beringia and Greenland regions became icebound in the Quaternary glaciation.[9][13][17]
Subspecies
That the merlin has a long-standing presence on both sides of the Atlantic is evidenced by the degree of genetic distinctness between Eurasian and North American populations. Arguably, they might be considered distinct species, with gene flow having ceased at least a million years ago, but probably more.[9]
By and large, color variation in either group independently follows Gloger's Rule. The Pacific temperate rain forest subspecies suckleyi's males are almost uniformly black on the upperside and have heavy black blotches on the belly, whereas those of the lightest subspecies, pallidus, have little non-dilute melanin altogether, with grey upperside and reddish underside pattern.[8]
Presumably coastal forest merlin (F. c. suckelyi), Potter Marsh, Anchorage (Alaska, United States)
The merlin is 24–33cm (9.4–13.0in) long with a 50–73cm (20–29in) wingspan.[19] Compared with most other small falcons, it is more robust and heavily built. Males average at about 165g (5.8oz) and females are typically about 230g (8.1oz). There is considerable variation, however, throughout the birds' range and—in particular in migratory populations—over the course of a year. Thus, adult males may weigh 125–210g (4.4–7.4oz), and females 190–300g (6.7–10.6oz). Each wing measures 18.2–23.8cm (7.2–9.4in), the tail measures 12.7–18.5cm (5.0–7.3in) and the tarsus measures 3.7cm (1.5in).[19][20] Such sexual dimorphism is common among raptors; it allows males and females to hunt different prey animals and decreases the territory size needed to feed a mated pair.[8][21]
The male merlin has a blue-grey back, ranging from almost black to silver-grey in different subspecies. Its underparts are buff- to orange-tinted and more or less heavily streaked with black to reddish brown. The female and immature are brownish-grey to dark brown above, and whitish buff spotted with brown below. Besides a weak whitish supercilium and the faint dark malar stripe—which are barely recognizable in both the palest and the darkest birds—the face of the merlin is less strongly patterned than in most other falcons. Nestlings are covered in pale buff down feathers, shading to whitish on the belly.[21]
The remiges are blackish, and the tail usually has some three to four wide, blackish bands, too. Very light males only have faint and narrow medium-grey bands, while in the darkest birds the bands are very wide, so that the tail appears to have narrow lighter bands instead. In all of them, however, the tail tip is black with a narrow white band at the very end, a pattern possibly plesiomorphic for all falcons. Altogether, the tail pattern is quite distinct though, resembling only that of the aplomado falcon (F. berigora) and (in light merlins) some typical kestrels. The eye and beak are dark, the latter with a yellow cere. The feet are also yellow, with black claws.[21]
Light American males may resemble the American kestrel (F. sparverius, not a typical kestrel), but merlin males have a grey back and tail rather than the reddish-brown of the kestrels. Light European males can be distinguished from kestrels by their mainly brown wings. In the north of South Asia, wintering males may be confused with the red-necked falcon (F. chicquera) if they fly away from the observer and the head (red on top in F. chicquera) and underside (finely barred with black in F. chicquera) are not visible.[21]
Ecology
Merlins inhabit fairly open country, such as willow or birch scrub, shrubland, but also taiga forest, parks, grassland such as steppe and prairies, or moorland. They are not very habitat-specific and can be found from sea level to the treeline. In general, they prefer a mix of low and medium-height vegetation with some trees, and avoid dense forests as well as treeless arid regions. During migration however, they will utilize almost any habitat.[8]
Most of its populations are migratory, wintering in warmer regions. Northern European birds move to southern Europe and North Africa, and North American populations to the southern United States to northern South America. In the milder maritime parts of its breeding range, such as Great Britain, the Pacific Northwest and western Iceland, as well as in Central Asia, it will merely desert higher ground and move to coasts and lowland during winter. The migration to the breeding grounds starts in late February, with most birds passing through the US, Central Europe and southern Russia in March and April, and the last stragglers arriving in the breeding range towards the end of May. Migration to winter quarters at least in Eurasia peaks in August/September, while e.g. in Ohio, just south of the breeding range, F. c. columbarius is typically recorded as a southbound migrant as late as September/October.[8][18] In Europe, merlins will roost communally in winter, often with hen harriers (Circus cyaneus). In North America, communal roosting is rare.
Merlins rely on speed and agility to hunt their prey. They often hunt by flying fast and low, typically less than 1m (3.3ft) above the ground, using trees and large shrubs to take prey by surprise. But they actually capture most prey in the air, and will "tail-chase" startled birds. Throughout its native range, the merlin is one of the most able aerial predators of small to mid-sized birds, more versatile if anything than the larger hobbies (which prefer to attack in mid-air) and the more nimble sparrowhawks (which usually go for birds resting or sleeping in dense growth). Breeding pairs will frequently hunt cooperatively, with one bird flushing the prey toward its mate.[8][22]
The merlin will readily take prey that is flushed by other causes, and can for example be seen tagging along sharp-shinned hawks (Accipiter striatus) to catch birds that escape from this ambush predator into the open air. It is quite unafraid, and will readily attack anything that moves conspicuously. Merlins have even been observed trying to "catch" automobiles and trains, and to feed on captive birds such as those snared in the mist nets used by ornithologists. Even under adverse conditions, one in 20 targets is usually caught, and under good conditions almost every other attack will be successful. Sometimes, merlins cache food to eat it later.[8][23]
In particular during the breeding season, most of the prey are smallish birds weighing 10–40g (0.35–1.41oz). Almost any such species will be taken, with local preferences for whatever is most abundant—be it larks (Alaudidae), pipits (Anthus), finches (Fringillidae),[24]house sparrows (Passer domesticus), other Old World sparrows (Passeridae), northern wheatears (Oenanthe oenanthe), true thrushes (Turdus), kinglets (Regulidae)[25] or buntings (Emberiza)[24]—and inexperienced yearlings always a favorite. Smaller birds will generally avoid a hunting merlin if possible. In the Cayman Islands (where it only occurs in winter), bananaquits were noted to die of an apparent heart attack or stroke, without being physically harmed, when a merlin went at them and they could not escape.[23]
Corvids are the primary threat to eggs and nestlings. Adult merlins may be preyed on by larger raptors, especially peregrine falcons (F. peregrinus), eagle-owls (e.g., great horned owl, Bubo virginianus), and larger Accipiterhawks (e.g., northern goshawk, A. gentilis). In general however, carnivorous birds avoid merlins due to their aggressiveness and agility. Their desire to drive larger raptors away from their territory is so pronounced that it is an identifying characteristic. Quoting from one popular raptor watching reference,[37] "An observer may use this aggressive tendency for identification purposes and as a means of detection. High-flying merlins often betray themselves and distinguish themselves because they are vigorously harassing another raptor (even ones as large as the Golden Eagle)."
Breeding occurs typically in May/June. Though the pairs are monogamous at least for a breeding season, extra-pair copulations have been recorded. Most nest sites have dense vegetative or rocky cover; the merlin does not build a proper nest of its own. Most will use abandoned corvid (particularly Corvus crow and Pica magpie) or hawk nests which are in conifer or mixed tree stands. In moorland—particularly in the UK—the female will usually make a shallow scrape in dense heather to use as a nest. Others nest in crevices on cliff-faces and on the ground, and some may even use buildings.[8]
Three to six (usually 4 or 5) eggs are laid. The rusty brown eggs average at about 40mm ×31.5mm (1.57in ×1.24in).[citation needed] The incubation period is 28 to 32 days. Incubation is performed by the female to about 90%; the male instead hunts to feed the family. Hatchlings weigh about 13g (0.46oz). The young fledge after another 30 days or so, and are dependent on their parents for up to 4 more weeks. Sometimes first-year merlins (especially males) will serve as a "nest helper" for an adult pair. More than half—often all or almost all—eggs of a clutch survive to hatching, and at least two-thirds of the hatched young fledge. However, as noted above, in years with little supplementary food only 1 young in 3 may survive to fledging. The merlin becomes sexually mature at one year of age and usually attempts to breed right away. The oldest wild bird known as of 2009 was recorded in its 13th winter.[8][38]
Relationship with humans
A male smyril is featured on this Faroese stamp by Edward Fuglø
John James Audubon illustrated the merlin in the second edition of Birds of America (published in London, 1827–38) as Plate 75, under the title, "Le Petit Caporal – Falco temerarius". The image was engraved and colored by Robert Havell's London workshops. The original watercolor by Audubon was purchased by the New York History Society,[39] where it remains as of January 2009.
William Lewin illustrates the merlin as Plate 22 in volume 1 of his Birds of Great Britain and their Eggs, published 1789 in London.
Use in falconry
In medieval Europe, merlins were popular in falconry: the Book of St. Albans listed it as "the falcon for a lady", where it was noted for classic "ringing" (circling rapidly upward) pursuits of the English skylark.[40] Though the merlin is only slightly larger than the American kestrel in dimensions, it averages about one third to one half larger by weight, with this weight mostly being extra muscle that gives it greater speed and endurance than the kestrel.[40] Like the American kestrel, the merlin offers the modern falconer the ability to hunt year round against sparrows and starlings, in urban settings not requiring large tracts of land or hunting dogs, with the additional advantage of being able to reliably take small game birds such as dove and quail during hunting season. A large and exceptionally aggressive female merlin may take prey as large as pigeons and occasionally even small ducks.[41] They also offer an exciting style of flight, generally at closer range than large falcons where it may be more clearly witnessed and enjoyed by the falconer. In addition to horizontal tail-chases in the manner of American kestrels, they will also "ring up" in pursuit of prey that seeks to escape by out-climbing them, and perform high speed diving stoops on prey beneath them in the manner of larger falcons. Quoting from one popular falconry book on the eagerness of merlins to chase a swung lure, "Every stoop, outrun, dodge, and aerial maneuver of a hard flight to real quarry can be duplicated with no risk of loss of the falcon. Merlins regularly flown to the lure take most field quarries with such ease and such assurance as to make the field flight the less interesting and exciting of the two."[40]
Quoting expert falconer Matthew Mullenix, author of the book "American Kestrels in Modern Falconry", in an article comparing the American kestrel to the merlin he states "What a merlin gives you is raw power: lots of it. It brings an ability to negate wind as a factor, to stay airborne at a tremendous clip then gear down further at any time for more performance. One merlin can dominate an entire flock of frightened birds, directing its fate as a whole. The flock responds like bait fish to a barracuda and for precisely the same reason. Merlins demonstrate total mastery of their element."[42] Concerning suitable game for these two species, he states "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."
Status and conservation
Hunter with trained merlin, Jandari Lake, Georgia SSR, November 1979
Altogether, the merlin is not particularly rare, and due to this and its wide range it is considered a species of least concern by the IUCN.[1] Its numbers are—except in the Asian part of its range, where the situation is less well determined—regularly censused. In about every major country it inhabits, many hundreds to many thousands are found, ranging from a "mere" 250–300 pairs in Belarus to perhaps as many as 30,000 pairs of aesalon in European Russia as determined in 1993. It is listed on CITES Appendix II and on a local level protected as other birds of prey; while some countries allow to capture merlins, e.g. for falconry, international trade requires an export permit.[1][8]
By far the most serious long-term threat to these birds is habitat destruction, especially in their breeding areas. Ground-nesting populations in moorland have a preference for tall heather, and are thus susceptible to overmanagement by burning vast tracts instead of creating a habitat mosaic containing old and new growth. Still, the merlin is rather euryoecious (adaptable to various conditions) and will even live in settled areas, provided they have the proper mix of low and high vegetation, as well as sufficient prey (which is usually the case) and nesting sites (which is a common limiting factor).[8]
In North America, the species seems to have been more widespread in the past, or perhaps its range has shifted northwards: F. c. columbarius was an uncommon breeding bird in Ohio before the 20th century, but in Seneca County, as early as the 1900s even single adults were rarely seen in the breeding season. It is encountered in Ohio as a passage migrant and rarely as a winter guest, though two recent nestings have been confirmed. Changing land-use in Ohio mainly turned forest into agricultural land and thus is not very likely to have rendered the region inhospitable to the merlin; global warming on the other hand cannot be dismissed as a reason, given that the merlin is essentially a subarctic species that barely ranges even into temperate climes. Also, it may be that the number of merlins wintering in the northern USA has increased during the 20th century.[11][8][18]
Perhaps the most frequent cause of accidental death for individuals is collision with man-made objects, particularly during attacks. This may account for almost half of all premature deaths of merlins. In the 1960s and 1970s, organochlorine pesticides were responsible for declines—particularly in Canada—due to eggshell thinning and subsequent brood failure, and compromising the immune system of adults. This has since been remedied with restrictions on the use of DDT and similar chemicals, and numbers have rebounded. Overall, merlin stocks appear globally stable; while they may decline temporarily in places, they will usually increase again eventually, suggesting that this phenomenon is due to the fluctuations of supplementary food stocks discussed above.[8]
Falcons are birds of prey in the genus Falco, which includes about 40 species. Some small species of falcons with long, narrow wings are called hobbies, and some that hover while hunting are called kestrels. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene.
The peregrine falcon, also known simply 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 back, barred white underparts, and a black head. The peregrine is renowned for its speed. It can reach over 320 km/h (200 mph) during its characteristic hunting stoop, making it the fastest animal on the planet. According to a National Geographic TV program, the highest measured speed of a peregrine falcon is 389 km/h (242 mph). As is typical for bird-eating (avivore) raptors, peregrine falcons are sexually dimorphic, with females being considerably larger than males.
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 involved in falconry: a "falconer" flies a falcon; an "austringer" keeps Goshawks and uses accipiters for hunting. In modern falconry, the red-tailed hawk, Harris's hawk, and the peregrine falcon are some of the more commonly used birds of prey. The practice of hunting with a conditioned falconry bird is also called "hawking" or "gamehawking", although the words hawking and hawker have become used so much to refer to petty traveling traders, that the terms "falconer" and "falconry" now apply to most use of trained birds of prey to catch game. However, many contemporary practitioners still use these words in their original meaning.
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.
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.
The sharp-shinned hawk or northern sharp-shinned hawk, commonly known as a sharpie, is a small hawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than some Neotropical species, such as the tiny hawk. The taxonomy is far from resolved, with some authorities considering the southern taxa to represent three separate species: white-breasted hawk, plain-breasted hawk, and rufous-thighed hawk. The American Ornithological Society and some other checklists keeps all four variations conspecific.
The American kestrel, 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. 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 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.
The broad-winged hawk is a medium-sized hawk of the genus Buteo. During the summer, some subspecies are distributed over eastern North America, as far west as British Columbia and Texas; they then migrate south to winter in the Neotropics from Mexico south to southern Brazil. Other subspecies are all-year residents on Caribbean islands. As in most raptors, females are slightly larger than males. Broad-winged hawks' wings are relatively short and broad with a tapered, somewhat pointed appearance. The two types of coloration are a dark morph with fewer white areas and a light morph that is more pale overall. Although the broad-winged hawk's numbers are relatively stable, populations are declining in some parts of its breeding range because of forest fragmentation.
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.
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.
Harris's hawk, formerly known as the bay-winged hawk or dusky hawk, and known in Latin America as the 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.
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.
The plumbeous kite is a bird of prey in the family Accipitridae that is resident in much of northern South America. It is migratory in the northern part of its range which extends north to Mexico. It feeds on insects which it catches either from a perch or while in flight.
The Seychelles kestrel is a small bird of prey belonging to the genus Falco in the falcon family, Falconidae. It is endemic to the Seychelles Islands where it is the only breeding bird of prey. It is known in Seychellois Creole as the katiti after its loud, shrill call.
The fox kestrel is a bird of prey belonging to the falcon family Falconidae. It is found in arid, open country in the northern part of Sub-Saharan Africa.
The grey kestrel is an African bird of prey belonging to the falcon family Falconidae. Its closest relatives are the banded kestrel and Dickinson's kestrel and the three are sometimes placed in the subgenus Dissodectes.
Dickinson's kestrel is a bird of prey of southern and eastern Africa belonging to the falcon family Falconidae. It is named after John Dickinson, an English physician and missionary who collected the type specimen. It is also known as the white-rumped kestrel. Its closest relatives are the grey kestrel and banded kestrel and the three are sometimes placed in the subgenus Dissodectes.
The banded kestrel is a bird of prey belonging to the falcon family Falconidae. It is endemic to Madagascar and is also known as the Madagascar banded kestrel, barred kestrel or Madagascar barred kestrel. Its closest relatives are the grey kestrel and Dickinson's kestrel of mainland Africa and the three are sometimes placed in the subgenus Dissodectes.
The gyrfalcon, the largest of the falcon genus, 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.
Hawkwatching is a mainly citizen science activity where experienced volunteers count migratory raptors in an effort to survey migratory numbers. Groups of hawkwatchers often congregate along well-known migratory routes such as mountain ridges, coastlines and land bridges, where raptors ride on updrafts created by the topography. Hawkwatches are often formally or informally organized by non-profit organizations such as an Audubon chapter, state park, wildlife refuge or other important birding area. Some hawkwatches remain independent of any organizing structure.
↑ Groombridge, Jim J.; Jones, Carl; Bayes, Michelle K.; van Zyl, Anthony J.; Carrillo, José; Nichols, Richard A.; Bruford, Michael W. (2002). "A molecular phylogeny of African kestrels with reference to divergence across the Indian Ocean". Molecular Phylogenetics and Evolution. 25 (2): 267–277. Bibcode:2002MolPE..25..267G. doi:10.1016/S1055-7903(02)00254-3. PMID12414309.
1 2 Ferguson-Lees, James; Christie, David A. (2001). Raptors of the World. Boston: Houghton Mifflin. ISBN0-618-12762-3.
↑ Davis, Kate (2002). Falcons of North America. Mountain Press Publishing Company.
1 2 3 4 White, Clayton M.; Olsen, Penny D.; Kiff, Lloyd F. (1994). "Family Falconidae". In del Hoyo, J.; Elliot, A.; Sargatal, J. (eds.). Handbook of Birds of the World. Vol.2: New World vultures to Guineafowl): 216–275, plates 24–28. Barcelona: Lynx Edicions. ISBN84-87334-15-6.
↑ Ferguson-Lees, J. & Christie, D.A. & Franklin, K. & Mead, D. & Burton, P.. (2001). Raptors of the world. Helm Identification Guides.
↑ 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): 160–174. doi:10.1111/mam.12060.
↑ Ferguson-Lees, J. & Christie, D.A. & Franklin, K. & Mead, D. & Burton, P.. (2001). Raptors of the world. Helm Identification Guides.
↑ Ferguson-Lees, J. & Christie, D.A. & Franklin, K. & Mead, D. & Burton, P.. (2001). Raptors of the world. Helm Identification Guides.
"Falco columbarius, Pigeon Hawk"; from American Ornithology 2nd edition, volume 1 (1828) by Alexander Wilson and George Ord. Colour plate from 1st edition by A. Wilson.
"The Pigeon Hawk" and "Le Petit Caporal", John James Audubon, Ornithological Biography volume 1 (1831). At Pigeon Hawk; Petit Caporal, in the appendix to Ornithological Biography volume 5 (1839), Audubon notes that his Falco temerarius of volume 1 was a small male merlin, and that this was brought to his attention by Charles Bonaparte, nephew of "the little corporal". Illustration from Birds of America octavo edition, 1840.
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