Peregrine Falcon
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[Photo] Adult Mediterranean Peregrine Falcon, Falco peregrinus brookei. Falco peregrinus, Taken on Covadonga, Asturias, Spain on October 2005. Date Oct 2005. Author Francisco M. Marzoa Alonso

The Peregrine Falcon (Falco peregrinus) is a cosmopolitan bird of prey in the family Falconidae. It is occasionally known in North America as Duck Hawk (see also American Kestrel, Merlin) though it is not closely related to true hawks. It is a medium-sized falcon, about the size of a large crow.

Its breeding range includes the Arctic tundra, through Europe, and North America, and south into Africa, South America, the Pacific Islands and Australia. Essentially, this species can be found everywhere on Earth (though only as a winter visitor in some areas), except in the polar regions, on very high mountains, in deserts, and most tropical rainforests. The only major ice-free landmass from which it is entirely absent is New Zealand. Both the English and scientific names of this species mean "wandering falcon", and refer to the species' wide range and its highly migratory habits.

Description
The Peregrine Falcon is a large falcon, with a wingspan of around 80???120 cm (31???47 inches) and a body length of 34???50 cm (13???20 in). The male and female have similar markings and plumage, but as usual in birds of prey the Peregrine Falcon displays marked sexual dimorphism in size, with the female measuring up to 30 percent larger than the male. The male weighs 570???710 g (20-25 oz); the noticeably larger female weighs 910???1500 g (32-53 oz). The female of the North American subspecies averages 32-34 oz (900-960 g), while the male averages 18-20 oz (500-570 g).

The back and the long and pointed wings of the adult Peregrine Falcon are usually bluish black to slate grey with indistinct darker barring (see "Subspecies" below); the wingtips are black. The underparts are white to rusty and barred with thin clean bands of dark brown or black. The tail, colored like the back but with thin clean bars, is long, narrow and rounded at the end with a black tip and a white band at the very end. The top of the head and a "moustache" along the cheeks are black, contrasting sharply with the pale sides of the neck and white throat. The cere is yellow, as are the feet, and the beak and claws are black. The upper beak is notched near the tip, an adaptation which enables falcons to kill prey by severing the spinal column at the neck.

The young bird is much browner with streaked, rather than barred, underparts, and has a pale bluish cere.

Taxonomy and systematics
The scientific name Falco peregrinus, means "wandering falcon" in Latin. Indeed, the species' common name refers to its wide-ranging flights in most European languages. The Latin term for falcons, falco, is related to falx, the Latin word meaning sickle, in reference to the silhouette of the falcon's long, pointed wings in flight.

The Peregrine Falcon belongs to a lineage of its genus which also includes the hierofalcons and the Prairie Falcon. This lineage probably diverged from other falcons as part of a general diversification of the genus at the end of the Late Miocene or in the Early Pliocene, about 8-5 million years ago (mya). As the Peregrine-herofalcon group includes both Old World and North American species, it is likely that the lineage originated in western Eurasia or Africa. Its relationship to other falcons is not clear; it might be close to the Red-necked Falcon and/or the American Kestrel which is not related to the "typical" kestrels and has a similar syrinx morphology as the Peregrine and the hierofalcons, but more research is required to resolve this; the issue is complicated by widespread hybridization confounding mtDNA sequence analyses; for example a genetic lineage of the Saker Falcon is known which originated from a male Saker producing fertile young with a female Peregrine ancestor some 100,000 years ago. Today, Peregrines are occasionally hybridized with other species such as Lanner Falcons to produce the "perilanner", a somewhat popular bird in falconry as it combines the Peregine's hunting skill with the Lanner's hardiness, or the Gyrfalcon to produce large, strikingly-colored birds for experienced falconers. As can be seen, the Peregrine is still genetically close to the hierofalcons, though their lineages diverged in the Late Pliocene (maybe some 2.5-2 mya in the Gelasian).

Fossil remains of a hierofalcon-like large Falco are known from the Early Pliocene of Bulgaria to the Early Pleistocene of southern and central Europe. Given the large range in time and that the fossil history of the Peregrine-Barbary complex is documented since the Early Pleistocene, it might be more than one species. It is interesting to note that the remains straddle the proposed divergence point of the Peregine complex and the hierofalcons in time and are geographically close to the region where the split presumably occurred (the general region of North Africa or the Mediterranean basin). Unfortunately, the specimens are fully fossilized, making them useless for molecular biological studies. Even so, time and place strongly indicate that these bones belong to a bird very close to if not actually the common ancestor to the Peregrine/Barbary complex and the hierofalcons, and/or an early representative of either lineage: The ecological niche for large falcons is at least today generally not sufficient to permit more than two species to exist in any one locality and given that this applies in all kinds of habitat, it is likely that this was already so during the Pliocene-Pleistocene boundary regardless the different climate and associated habitat distribution at that time.

Subspecies
Numerous subspecies of the Peregrine Falcon have been described:

Falco peregrinus peregrinus Tunstall, 1771 - includes brevirostris, germanicus, rhenanus, riphaeus
The nominate subspecies, breeding over much of temperate Eurasia between the tundra in the N and the Pyrenees, Mediterranean region and Alpide belt in the S. Mainly non-migratory in Europe, mainly migratory in Asia.
Falco peregrinus japonensis Gmelin, 1788 - includes kleinschmidti and pleskei. harterti seems to refer to intergrades with calidus.
NE Siberia to Kamchatka (possibly replaced by pealei on coast there) and Japan. Northern populations migratory, those of Japan resident.
Similar to peregrinus; young even darker than in anatum.
Falco peregrinus calidus Latham, 1790 - formerly leucogenys; includes caeruleiceps
Breeds in Arctic tundra of Eurasia, from Lapland to roughly Yana and Indigirka Rivers, Siberia. Completely migratory, travelling south in winter as far as sub-Saharan Africa.
Larger and paler than nominate, especially on crown.
Falco peregrinus macropus Swainson, 1837 - Australian Peregrine Falcon
Australia except in the SW; non-migratory.
Rather similar to brookei; slightly smaller and ear region all black. Feet are proportionally large.
Falco peregrinus peregrinator Sundevall, 1837 - Black Shaheen (or "Indian" Shaheen). Formerly sometimes known as Falco atriceps or Falco shaheen.
South Asia from Pakistan across India to Sri Lanka and SE China. Non-migratory.
Unmistakeable: small, dark, underparts rufous with lighter barring.
Falco peregrinus anatum Bonaparte, 1838 - the "Duck Hawk" proper (its scientific name literally means "Duck Peregrine Falcon"). At one time partly included in leucogenys.
Mainly found in the Rocky Mountains today. Formerly common throughout North America between the tundra and northern Mexico, where current reintroduction efforts seek to restore the population. Most mature anatums, except those that breed in more northern areas, winter in their breeding range. Most vagrants that reach western Europe seem to belong to the more northern and strongly migratory tundrius, only considered distinct since 1968.
Similar to nominate peregrinus but larger; adults somewhat paler and less patterned below but juveniles darker and more patterned below.
Falco peregrinus minor Bonaparte, 1850 - formerly often perconfusus (Stresemann fide Vaurie 1961)
Sparsely and patchily distributed throughout much of sub-Saharan Africa; widespread in Southern Africa and apparently reaches N along Atlantic coast as far as Morocco. Non-migratory.
Small and dark.
Falco peregrinus radama Hartlaub, 1861
Madagascar, Comoros. Non-migratory.
Falco peregrinus brookei Sharpe, 1873 - Mediterranean Peregrine Falcon or Maltese Falcon. Includes caucasicus and most specimens of proposed race punicus; others may be pelegrinoides Barbary Falcons (see also below) or perhaps the rare hybrids between these two which might occur around Algeria.
From Iberia around the Mediterranean (except in arid regions) to the Caucasus. Non-migratory.
Smaller that nominate; underside usually has rusty hue.
Falco peregrinus cassini Sharpe, 1873 - Austral Peregrine Falcon. Includes var. kreyenborgi (Pallid Falcon), a leucistic morph occurring in southernmost South America, long believed to be a distinct species (Ellis & Peres Garat 1983).
W South America from Ecuador (where very local) through Bolivia, N Argentina and Chile to Tierra del Fuego and Falkland Islands. Non-migratory.
Similar to nominate; slightly smaller and ear region black; var. kreyenborgi is medium grey above, has little barring below, and a head pattern like Saker Falcon but ear region white; see Ellis & Peres Garat (1983) for photos.
Falco peregrinus pealei Ridgway, 1873 - Peale's Falcon. Includes rudolfi.
Pacific Northwest of North America, northwards from the Puget Sound via British Columbia coast (including the Queen Charlotte Islands), along the Gulf of Alaska and the Aleutian Islands to the far eastern Bering Sea coast of Russia; possibly on the Kuril Islands and the coasts of Kamchatka also. Non-migratory.
The largest subspecies; looks like an oversized and darker tundrius or like a strongly barred and large anatum. Bill very wide. Juveniles occasionally have "blond" crowns.
Falco peregrinus ernesti Sharpe, 1894
Indonesia to Philippines and S to Papua New Guinea and Bismarck Archipelago; limits with nesiotes require confirmation. Non-migratory.
Very dark, dense barring on underside and black ear region.
Falco peregrinus submelanogenys Mathews, 1912 - Southwest Australian Peregrine Falcon.
SW Australia; non-migratory.
Falco peregrinus furuitii Momiyama, 1927
Volcano and possibly Bonin group, Ogasawara Islands. Non-migratory.
A rather dark form resembling pealei in color, but darker, especially on tail.
Falco peregrinus nesiotes Mayr, 1941
Fiji; probably also Vanuatu and New Caledonia. Non-migratory.
Falco peregrinus madens Ripley & Watson, 1963 - unusual in having some sexual dichromatism; if the Barbary Falcon is considered a distinct species, sometimes placed therein.
Cape Verde Islands; non-migratory.
Males have rufous wash on crown, nape, ears and back; underside conspicuously washed pinkish-brown. Females are tinged rich brown overall, especially on crown and nape.
Falco peregrinus tundrius C.M. White, 1968 - at one time included in leucogenys
Arctic tundra of North America to Greenland. Migrates to wintering grounds in Central and South America. Most vagrants that reach western Europe seem to belong to this subspecies, which was long united with anatum.
The New World equivalent to calidus; however, smaller than southern neighbor (anatum). Most have conspicuous white forehead and much white in ear region, but crown and "moustache" very dark (unlike in calidus). Juveniles browner, less grey, than in calidus, and paler, sometimes almost sandy, than in anatum.

The Barbary Falcon problem
A particular taxonomic problem is the Barbary Falcon or Red-naped Shaheen (or "Arabic" Shaheen, ??????????). These birds inhabit arid regions from the Canary Islands along the rim of the Sahara through the Middle East to Central Asia and Mongolia. They have a red neck patch but otherwise differ in appearance from the Peregrine proper merely according to Gloger's Rule. The genetic distance is slight and the supposed species form a close-knit and somewhat paraphyletic group in DNA sequence analyses. On the other hand, they differ more in behavior, ecology and anatomy than usual for conspecifics. They are able to produce fertile hybirds, but they are generally allopatric and only co-occur during breeding season in small areas around Punjab, Khorasan, and possibly the Maghreb and the Mongolian Altai, and there is clear evidence of assortative mating with hybridization hardly ever occurring under natural conditions.

Assuming a genetic distance of 2% in hierofalcons (Wink et al. 2004) corresponds to a divergence roughly 200,000-130,000 years ago (Nittinger et al. 2005), the 0.6-0.7% genetic distance in the Peregine-Barbary Falcon ("peregrinoid") complex (Wink et al., 2000) suggests its current taxa evolved in the Late Pleistocene some 100,000 years ago or less, but before the Upper Paleolithic. The presumed time of divergence between Peregrine and Barbary Falcons approximately coincides with the start of the last ice age, when desertification was prominent in North Africa and the Middle East, and the Persian Gulf became a landlocked inland sea that slowly dried up. Populations of ancestral "peregrinoid" falcons living in marginal habitat at the fringe of the African-Middle Eastern desert belt either adapted (and might have become isolated e.g. in the Persian Gulf region, which turned into semiarid habitat surrounded by vast deserts), or left for better habitat, or became extinct. During interstadials, deserts receded and the aridland and humidland populations could expand to contact again, causing some limited gene flow. This scenario by and large parallels the proposed evolutionary history of the Saker Falcon in relation to the other hierofalcons; indeed, that group shows similar patterns of molecular paraphyly though it is of somewhat earlier origin.

The fossil record adds little to the issue. A humerus some 9,000 years old (i.e., after the last ice age) from the Aswan area in Sudan, where Falco peregrinus minor occurs today, was identified to belong to the Peregrine (Tchernov 1968). It is not clear whether it was compared to a Barbary Falcon bone, but as habitat conditions then were nearly the same as today it is not likely to have been that taxon.

In conclusion, it is simply impossible to unequivocally resolve the issue whether the Barbary Falcon should be considered a species, or a subspecies complex of the Peregrine. It is apparent that the Barbary Falcons have completed some steps that make an evolutionary lineage a species (such as evolving a marked degree of reproductive isolation and morphological and ecological distinctness), but as evolution is a never-ending process and the taxa have no postzygotic reproduction barriers in place yet, the ultimate fate of the Barbary Falcon will decide itself in the next 10,000s to 100,000s of years (provided it does not become extinct in the meantime). It might eventually be subsumed again into a common gene pool with the Peregrine Falcon proper, or it might evolve into an unquestionably distinct species.

For the time being, it is perhaps worthwhile to note that the Barbary Falcon is one of the rare cases that may arguably be considered a species under the Biological, but certainly not under the Phylogenetic Species Concept rather than the other way around as usual. In addition, this case demonstrates that what makes a "species" is not just its descent, but also what happens to a population in the course of evolution, how it adapts, and how this affects its reproductive isolation (or lack thereof) from its sister taxa - and being coincident with the evolution of modern humans, it also illustrates the length of a speciation process: The lineages of the "peregrinoid" complex diverged about the time when stone-age humans were working with Aterian tools and were just starting to adorn their body with jewellery; the eventual outcome of the evolutionary process is unlikely to be resolved until 50,000 AD or later.

If the Barbary Falcon is included in Falco peregrinus, the following taxa are added:

Falco peregrinus pelegrinator Temminck, 1829
Canary Islands through N Africa and the Near East to Mesopotamia
Most similar to brookei but markedly paler above with rusty neck, light buff with reduced barring below.
Falco peregrinus babylonicus P.L. Sclater, 1861
E Iran along Hindu Kush and Tian Shan to Mongolian Altai ranges.
Paler than pelegrinator; somewhat similar to a small, pale Lanner Falcon

Ecology and behavior
The Peregrine Falcon lives mostly along mountain ranges, river valleys, coastlines, and increasingly in cities. In mild-winter regions, it is usually a permanent resident, and some individuals, especially adult males, will remain on the breeding territory. Populations that breed in colder climes typically migrate great distances during the northern winter.

The Peregrine Falcon is the fastest animal on the planet in its hunting dive, the stoop, in which it soars to a great height, then dives steeply at speeds of over 322 km/h (200 mph) hitting one wing of its prey, so as not to harm itself on impact. It should be noted, however, that in level flight the fastest-flying bird is the White-throated Needletail and either animal is often quoted as being the fastest on earth.

The average life span of a Peregrine Falcon is seventeen years in the wild, although some have been recorded to live more than twenty years of age. Apart from anthropogenic threats like collision with man-made objects, the Peregrine may be killed by large eagles, the Eurasian Eagle Owl, Gyrfalcon, Wildcat and Wolverine; inexperienced young may also be preyed upon by adult Peregrines.

Being nearly an apex predator, the Peregrine Falcon is host to a range of parasites and pathogens. It is a vector for Avipoxvirus, Newcastle disease virus, Falconid herpesvirus 1 (and possibly other Herpesviridae), and some mycoses and bacterial infections.
Endoparasites include Plasmodium relictum (usually not causing malaria in the Peregrine Falcon), a Leukocytozoon-like apicomplexan, Strigeidae trematodes, Serratospiculum amaculata (nematode), and tapeworms. Known Peregrine Falcon ectoparasites are chewing lice, Ceratophyllus garei (a flea), and Hippoboscidae flies (Icosta nigra, Ornithoctona erythrocephala).

Feeding habits
The Peregrine Falcon feeds almost exclusively on birds such as doves, waterfowl and songbirds. Occasionally it hunts small mammals, including bats, rats, voles, hares, mice and squirrels; the coastal populations of the large subspecies pealei feed almost exclusively on seabirds. Insects and reptiles make up a small proportion of the diet, which varies greatly depending on what prey is available. In urban areas, the Peregrine Falcon catches common city birds such as pigeons and Common Starlings. In many cities, it has been credited with controlling the numbers of such birds which are often considered pests, alleviating the need for controversial methods such as poisoning or hunting. Faced with starvation, the Peregrine Falcon may resort to cannibalism, eating its own chicks.

The Peregrine Falcon hunts at dawn and dusk, when prey is most active. It requires open space in order to hunt, and therefore often hunts over open water, marshes, valleys, fields and tundra. It searches for prey either from a high perch or from the air. Once prey is spotted, it begins a dive, called a stoop, folding tail and wings back, with feet held behind. The air pressure from a 200 mph dive could possibly damage a bird's lungs, but small bony tubercles in a falcon's nostrils guide the shock waves of the air entering the nostrils (compare intake ramps and inlet cones of jet engines) and enable the bird to breathe more easily while diving by reducing the change in air pressure. Prey is struck and captured in mid-air; the Peregrine Falcon strikes its prey with a clenched foot, stunning or killing it, then turns to catch it in mid-air. The Peregrine will drop it to the ground and eat it there if it is too heavy to carry. Prey is plucked before consumption.

Reproduction
The Peregrine Falcon first breeds at approximately two or three years of age. The pair mates for life and return to the same nesting spot annually. The courtship flight includes a mix of aerial acrobatics, precise spirals, and steep dives. The male passes prey it has caught to the female in mid-air. To make this possible, the female actually flies upside-down to receive the food from the male's talons. During the breeding season, the Peregrine Falcon is territorial; nesting pairs are usually more than 1 km (0.6 miles) apart, and often much farther, even in areas with large numbers of pairs. The distance between nests ensures sufficient food supply for pairs and their chicks. Within a breeding territory, a pair may have several nesting ledges; the number used by a pair can vary from one or two to seven in a 16-year period. The pair defends the chosen nest site against other Peregrines, and often against eagles or ravens.(Blood & Banasch 2001)

The Peregrine Falcon nests in a scrape, normally on cliff edges or, occasionally, on tall buildings or bridges. Cliff nests are generally located under an overhang, on ledges with vegetation, and south-facing sites are favored. The female chooses a nest site, where she scrapes a shallow hollow in the loose soil, sand, gravel, or dead vegetation in which to lay eggs. No nest materials are added. In remote, undisturbed areas such as the Arctic, steep slopes and even low rocks and mounds may be used as a nest site The Peregrine occasionally nests in tree hollows or in the disused nest of other large birds. The man-made structures used for breeding typically closely resemble the natural cliff ledges that the Peregrine prefers for its nesting locations.

Three to four eggs are laid in the scrape. The eggs are white to buff with red or brown markings. They are incubated for 29 to 33 days, mainly by the female. While the male also sometimes helps with the incubation of the eggs, it does so only occasionally and for short periods. The date of egg-laying varies according to locality, but is generally from February to March in the Northern Hemisphere, and from July to August in the Southern Hemisphere (the Australian subspecies macropus may breed as late as November and equatorial populatioons may nest anytime between June and December). The female generally lays another clutch if the eggs are lost early in the nesting season, though it is extremely rare is is rare in the Arctic owing to the short summer season. As a result of some infertile eggs and natural losses of nestlings, the average number of young found in nests is 2.5, and the average number that fledge is about 1.5.

After hatching, chicks are covered with creamy-white down and have disproportionately large feet. The "tiercel" (male) brings food to the female and chicks, but the chicks are fed by the female, which stays at the nest and watches the young. Chicks typically fledge 35 to 42 days after hatching, and remain dependent on their parents for up to two months (Snow 1994). When learning to fly, the fledglings practice the roll and the pumping of the wings before they master the actual stoop.

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