Peregrine Falcon

The Peregrine is a big, powerful falcon, about the size of a crow. Adults are blue-grey above, with a blackish hood and a broad black moustache that stands out against a white cheek and throat. The underparts are white or buff, plain on the upper breast and barred dark from there down. The cere at the base of the bill, the ring round the dark eye and the feet are yellow.

In flight the wings are long, broad at the base and tapered to a sharp point; perched, the wingtips reach almost to the tip of the tail. In normal flight the wingbeats are strong and fluid, becoming deeper and faster in a chase. Seen from below, an adult's underwings and body look closely barred, with the dark hood and pale throat standing out at the front.

British Peregrines are 39-50 cm (15-20 in) long, with a wingspan of 95-115 cm (37-45 in), and weigh 600-1,300 g (1.3-2.9 lb), which makes the Peregrine the UK's biggest falcon. Across the species' world range, males are 36-49 cm long and females 45-58 cm, and weights run from 410 g for a small male to 1,600 g for a big female.

Males and females look alike, but the female is much bigger: 15-20% larger and 40-50% heavier, with normally no overlap in size between the sexes within a subspecies.¹ In some subspecies she is also, on average, buffier below, with heavier markings reaching higher up the breast, and browner above. See Male vs female Peregrine Falcons.

Young Peregrines are brown rather than blue-grey above, with pale buff feather edges, and buff below with heavy dark streaks running lengthwise instead of bars. The moustache is usually narrower than an adult's. The cere and eye-ring are often bluish or greenish rather than yellow, and many young birds have bluish-grey to greenish feet, though many young in western North America have yellowish feet. They moult into adult plumage in their second year. See Juvenile Peregrine Falcons.

Three subspecies breed in North America. Most birds south of the tundra belong to anatum, dark-headed with a broad moustache. Tundra Peregrines (tundrius), from the Arctic, are paler, with a narrow moustache and large white cheeks, and adults have an unmarked white breast. Peale's Peregrines (pealei), of the Pacific Northwest coast and the Aleutian Islands, are the largest and darkest: slaty above and boldly spotted and streaked below.

British birds belong to the nominate race, peregrinus, one of 18 subspecies worldwide, which include the Barbary Falcon of the Canary Islands and North Africa east to Iran.²

A Hobby is much smaller, about the size of a Kestrel, with long, scythe-shaped wings; adults are streaked below, where an adult Peregrine is barred, and have rusty-red 'trousers' and undertail. A Merlin is smaller still and compact, with shorter wings, and has no dark hood or broad moustache. A Gyrfalcon, an Arctic falcon, is bigger and bulkier, with broader, more rounded wings and a longer tail; perched, its wingtips fall short of the tail tip, and all but the darkest Gyrfalcons lack the Peregrine's hooded look. In western North America the Prairie Falcon is sandy brown and paler, with a thin moustache and no hood, and shows dark patches in the wingpits in flight.

Young birds of other large falcons can look much like young Peregrines, and escaped falconry hybrids, part Peregrine and part Gyrfalcon or Prairie Falcon, are sometimes loose in the wild and easily mistaken for the real thing.

Peregrines are usually quiet away from the nest. Adults give a harsh kak-kak-kak, repeated rapidly and often for long spells, given in alarm and when the birds are defending their nest. Near the nest you may also hear a drawn-out, rising wail, given mostly before one of the pair passes food to the other, or by a lone male advertising for a mate. In courtship the male gives a fast chittering, and both birds give a three-part call in their displays on the nest ledge.

Young in the nest beg with a harsh, repeated screech, and the demanding wails of older young can carry 1.5-2 km. In one study in the north-eastern US, analysis of recordings identified individual birds from their alarm calls with 72-90% accuracy, and told males from females about 90% of the time.¹

Peregrines live on every continent except Antarctica and are among the most widely distributed birds in the world; they are absent as breeders only from a few large regions, such as the Amazon Basin, the Sahara and much of the steppe of central and eastern Asia.

In Britain and Ireland Peregrines can be seen all year. They breed on upland crags and sea cliffs, in quarries and, more and more, on tall structures in lowland towns and cities, on pylons, power stations, churches and cathedrals. Many upland birds move down to estuaries and coasts in winter. The breeding range has almost tripled since 1968-72, and the winter range in Britain has doubled since 1981-84, with gains mainly across lowland England.³

In North America Peregrines breed from the Arctic to northern Mexico, on cliffs, along coasts and rivers and in cities, and can be seen all year in much of the US, where many winter in cities.

It depends where they breed. British and Irish Peregrines are resident, but ringing shows birds moving both ways: the BTO's ringing records hold 215 reports of Finnish-ringed and 87 of Dutch-ringed Peregrines found in Britain and Ireland, and 47 of British and Irish birds found abroad, 30 of them in France. One ringed as a nestling in Northumberland in 1997 was found dead on Lanzarote, 3,066 km away, the following spring.⁴

Arctic Peregrines are long-distance migrants: some travel 25,000 km (15,500 miles) a year between the tundra and South America, and one ringed in Canada's Northwest Territories was found 14,500 km south in Argentina less than four months later. In autumn they follow coasts and barrier islands; Cape May, New Jersey, counted 1,503 in autumn 1996.¹ See Peregrine Falcon migration.

Peregrines eat birds, most of them caught in the air. Pigeons and doves, Rock Doves above all, whether wild, feral or domestic, usually make up the bulk of the diet wherever Peregrines live, alongside starlings, waders, ducks and many smaller birds. A few bats are taken too, and rarely voles, fish or insects. Surplus prey is often cached on a ledge or in a crevice to eat later.

The range of prey is huge: at least 429 bird species have been recorded as prey in North America, and worldwide the total is almost certainly more than 1,500 and probably more than 2,000. They have killed birds from hummingbirds to Sandhill Cranes, but most prey weighs 50-500 g, and the smaller male catches lighter birds than the female.¹

In UK cities, nest cameras at 31 sites in 27 cities over three breeding seasons, 2020-2022, recorded 8,227 prey items: starlings and pigeons, mostly feral, were the staple, with Rose-ringed Parakeets also important in London. Racing pigeons, recognised by their rings or wing stamps, made up 5.8-6.4% of the pigeons taken in London and 10.7-17% elsewhere.⁵

Most hunts fail: across 23 studies the average success rate was 23.7%, ranging from 7% to 83%.¹ See What do Peregrine Falcons eat?

Peregrines hunt by day, but in cities some also hunt at night. At the Empire State Building in New York, from August to November 2004, Peregrines made 111 hunting attempts on migrating birds after dark and caught 37.⁶ At 30 nest sites in UK towns and cities watched by webcam from 2019 to 2023, adults fed their young at night at least once in 28 of 66 nesting attempts, more often when the moon was between first and last quarter and where the night sky was more lit.⁷

Peregrines build no nest. The male shows the female several scrapes, hollows he has pressed into gravel, soil or old debris on a ledge, and she chooses one. Most natural sites are cliff ledges, typically about a third of the way down the face, and quarries; Peregrines also use the old stick nests of Ravens and other birds, on cliffs and pylons, and in a few places nest in trees or on the ground.

In the UK the average first-egg date in nest records is 6 April, ranging from 23 March to 28 April.³ Pairs usually first breed at two years old. See Peregrine Falcon nesting.

The eggs are creamy to reddish, spotted and blotched with warm browns and reds, and both parents incubate, the female most. The BTO gives a typical clutch of 3-4 eggs; UK nest records average 3.28 eggs (2-5) and an incubation of about 31 days (29.5-33.5),³ while Birds of the World puts it at 33-35 days and says the 28-29 days often quoted is too short.¹

The young first fly at about 39 days in UK nest records (35-44),³ and then may depend on their parents for another 5-6 weeks in migratory populations and 9-10 weeks where Peregrines are resident; a pair raises one brood a year, but if the eggs are lost early it may lay again, usually within about two weeks.¹

Tall buildings now hold many of Britain's Peregrines. The 2014 national survey estimated 825 pairs in England against 469 in 2002, so that England held more pairs than Scotland, where numbers fell from 573 to 523; much of the gain was in lowland England, probably helped by pairs taking up nest sites on buildings and other structures.^{14, 15} A study of 22 urban and 58 rural nest sites in Britain from 2006 to 2016 found that urban pairs fledged more young and nested more successfully.¹⁶ Many town pairs nest in boxes or trays put up for them, where they often raise more young than at natural sites.¹

In North America a female on the Sun Life building in Montreal nested there from 1940 to 1952 and raised 22 young.¹⁷ By 2003 city nesting was common there: only 32% of pairs in the Midwest and Northeast nested on natural sites, against 92% elsewhere.¹⁸

The Peregrine's best-known way of hunting is the stoop: from high above its target it folds its wings against its body and dives, usually at 30-60 degrees and from 215-320 m (705-1,050 ft) up, to overtake a bird in flight and strike or grab it. Speeds near the theoretical maximum need a drop of more than 1,000 m.¹ Many attacks are not stoops at all: of 12 live hunts filmed by cameras on captive falcons, 4 began with a stoop and the rest as level chases, and the falcons steered to their target by the same rule many guided missiles use.⁸

The 389 km/h (242 mph) often quoted as the Peregrine's top speed is the fastest dive speed recorded with an instrument on a Peregrine, and it came from one captive, imprinted, trained falcon, Frightful, in skydives in 1999. She was released from a plane at 5,180 m (17,000 ft) and fell beside her skydiving owner, falconer Ken Franklin, while a National Geographic film was being made, and a small recording altimeter on her tail measured how far she fell in a set time. The figure has not appeared in a peer-reviewed paper, and some falcon experts called the work artificial.^{9, 10}

Free-flying Peregrines have been measured going more slowly. In a radar study of four stoops by a Peregrine and a Goshawk, the Peregrine's fastest 10-second averages were 31-39 m/s, about 112-140 km/h (69-87 mph).¹¹ What was probably a single wild male at a nest cliff in Colorado, followed with an optical tracking device from 1995 to 1998, was typically flying at 144-252 km/h (89-157 mph) over the ground when it went out of view; the researchers gave these as raw figures, without corrections. Falcons there approached prey from as far as 1,500 m away along a curved path that let them keep their head straight while one eye stayed on the target.¹² A 1998 model calculated that an 'ideal falcon' diving straight down could reach roughly 320-400 km/h (200-250 mph), assuming the drag measured in slow flight, and its author warned that the model does not necessarily describe real falcons.¹³

Studies brought together in Birds of the World put a Peregrine's ordinary cruising flight at an average of 40-55 km/h (25-34 mph), rising to about 112 km/h (70 mph) in a chase.¹ See The fastest birds in the world.

Outside the breeding season most Peregrines live alone, though pairs that stay on their territory may be seen together all year. A pair defends its nest cliff hard against other Peregrines and other birds of prey, and fights between two birds of the same sex can end in death. Courtship includes high soaring, fast figure-of-eight flights along the cliff and food passes in the air, the female rolling over to take prey from the male's feet. Pairs sometimes hunt together, one flying at a flock while the other stoops on a straggler.

A Peregrine that survives to breeding age lives about seven years on average; about 81% of adults and 60% of first-year birds survive each year.³

The oldest on record in Britain and in Europe is a male ringed as a nestling in Cumbria on 7 June 1994 and identified alive by its transponder tag near Lochmaben, Dumfries and Galloway, on 1 May 2016, 21 years 10 months and 24 days after ringing; EURING's European longevity list, which gives ages to the nearest month, lists the same bird at 21 years 10 months; Europe's next oldest is a Finnish bird of 21 years 7 months that was found dead.^{19, 20} In North America the oldest is a Peregrine banded as a nestling in Minnesota in 1992, whose band was read on the live bird in Minnesota in 2012, at an age of at least 19 years 9 months.²¹

Adult Peregrines are usually killed only by large birds of prey: eagles, Gyrfalcons and, at night, Great Horned Owls in North America, while Eagle-Owls are thought to limit where Peregrines nest in parts of France where cliffs are few. Eggs and young face more. Of 455 recorded deaths of Peregrines in the US Midwest up to 2000, 78 were collisions with buildings, 50 with vehicles, 19 were killed by other Peregrines and 10 were shot.¹ In cities, young birds also drown after falling from nests on bridges.

The Peregrine is listed as Least Concern worldwide, with an estimated 100,000-499,999 mature birds, a number BirdLife International suspects is increasing, and it is Green-listed in the UK and in Ireland.^{22, 23, 24, 25}

The 2014 national survey estimated 1,769 pairs across the UK, the Isle of Man and the Channel Islands, 22% more than in 2002, with most of the increase in lowland England and declines in some upland areas, and by 2014 the population may have been the biggest it had ever been.^{15, 14} The Breeding Bird Survey, a survey of randomly chosen squares in which Peregrines are scarce, shows a UK fall of 57% from 1995 to 2024 and 49% over the last ten years.²⁶

In North America numbers have risen since the 1970s. The North American Breeding Bird Survey shows a rise of 1.79% a year from 1966 to 2025, though it meets so few Peregrines that it gives its own figure the lowest credibility rating.²⁷ Partners in Flight puts the US and Canadian population at more than 72,000 birds.²⁸

The UK and Isle of Man had about 874 pairs of Peregrines in the 1930s and only 385 by 1961.³ During the Second World War, orders from 1940 allowed Peregrines to be destroyed to protect the messenger pigeons of the National Pigeon Service, and in southern England they were almost wiped out between 1940 and 1945.^{29, 30} After a partial recovery the population of Great Britain crashed again between 1956 and 1963, seeming to level off at about 44% of pre-war numbers.³⁰

The main cause was organochlorine pesticides. Dieldrin and aldrin seed dressings poisoned adults, and DDE, the residue of DDT, thinned eggshells: Peregrine eggshells in Britain became thinner from 1946-47, by 19.1% nationally, and egg breakage was recorded 47 times in 168 eyries examined in 1951-66, against 3 times in 109 in 1904-50.^{30, 31} As pesticide problems eased, the population recovered, to an estimated 1,283 pairs in 1991, 147% of the 1930s level.³²

In North America the crash was worse. By the mid-1960s Peregrines were essentially gone from the eastern US east of the Mississippi, and a 1964 survey of 133 old nest sites in the eastern US and Canada's Maritime provinces found none in use.³³ In the US, eggshell thinning in three declining birds of prey began in 1947 and reached 19% or more.³⁴ Canada banned DDT in 1970 and the US in 1972, and from 1974 about 6,000 captive-bred young were released across North America. By 1998 there were 1,650 known pairs in the US and Canada, and on 25 August 1999 the American Peregrine was removed from the US endangered list, five years after the Arctic subspecies, and by 2003 there were 3,005 pairs of the American subspecies in the US, Canada and Mexico.^{33, 18}

In the UK the Peregrine is on Schedule 1 of the Wildlife and Countryside Act and of the Wildlife (Northern Ireland) Order. As well as the protection every wild bird has, it is an offence to disturb one, intentionally or recklessly, while it is building a nest or is at or near a nest with eggs or young, or to disturb its dependent young, without a licence.^{35, 36, 37} Captive Peregrines in Great Britain must be registered and ringed, and in the Republic of Ireland it is a protected wild bird.^{36, 38}

Illegal persecution is still thought to limit numbers in the uplands, and on grouse moors in northern England pairs have raised 50% fewer young than pairs in other habitats there.³ The RSPB confirmed at least 154 Peregrines as victims of persecution in the UK from 2009 to 2023, including 89 shot or shot at and 51 poisoned,³⁹ and says eggs and chicks are still taken illegally for collections and falconry.⁴⁰

In the US the Peregrine is protected by the Migratory Bird Treaty Act, which covers the bird and any part, nest or egg of it.^{41, 42} Falconers need a permit from their state, tribe or territory, and apprentices may not take a wild Peregrine; the number of first-year migrants that may be taken is capped, at 144 a year east of 100 degrees west since 2017.^{43, 44} The Eurasian subspecies, to which British birds belong, is still listed as endangered under the US Endangered Species Act, as a foreign species, since 1976.⁴⁵ In Canada falcons are not covered by the federal Migratory Birds Convention Act, though they may be protected by provincial and territorial laws, and Peale's Peregrine is listed as of Special Concern under the Species at Risk Act.^{46, 47}