Peregrine falcon

• 1. Introduction

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  The peregrine falcon has been credited with a dive of 389 kilometres per hour. A National Geographic television program reported in 2005 that a falcon recorded by Ken Franklin reached that speed. Radar tells a more cautious story. The highest speed it has reliably measured is 184 kilometres per hour. Between those two numbers lies one of the most argued-over claims in the natural world.

  This documentary follows a bird found nearly everywhere on Earth, from the Arctic tundra to the tropics. What is a body built for such speed actually like? How did a pesticide push the species out of whole regions, and what brought it back? And why would a bird of cliffs and open sky end up nesting in the middle of towns?

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• 2. Name and Kin

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  In 1771, the English ornithologist Marmaduke Tunstall gave the bird the name Falco peregrinus in his work Ornithologia Britannica. The phrase itself was much older. Albertus Magnus had used it in 1225. Peregrinus is Latin for one from abroad. The likely reason is that falconers took young birds while they were travelling to their breeding grounds, because cliff nests are hard to reach. Falco is linked to a word for sickle, a reference to the curved outline of the long pointed wings in flight. The English name and the scientific name both mean wandering falcon.

  Around 3-8 million years ago, the lineage holding the peregrine, the hierofalcons and the prairie falcon, Falco mexicanus, split from other falcons. Because the group includes both Old World and North American species, it probably began in western Eurasia or Africa. Widespread hybridization muddies the genetic evidence. One lineage of the saker falcon, Falco cherrug, began when a male saker fathered fertile young with a female peregrine ancestor, and their descendants kept breeding with sakers.

  The IOC World Bird List accepts 18 subspecies, while the 1994 Handbook of the Birds of the World accepts 19. The gap comes from the Barbary falcon of the Canary Islands and coastal North Africa. The handbook counts it as two subspecies rather than a separate species. Its genetic difference from the peregrine is only about 0.6-0.8%, which suggests a split during the Last Ice Age. All major ornithological authorities now treat it as a subspecies. It has a red neck patch and a habit of beating only the outer part of its wings, as fulmars sometimes do. It breeds at different times of year from neighbouring peregrines but can still interbreed with them.

  At the small end, the African subspecies minor has males weighing as little as about 300 g. At the large end, Peale's falcon lives along the Pacific coast from Puget Sound through the Aleutian Islands, with females reaching 1500 g and a notably wide bill. In southernmost South America, a pale form called the pallid falcon was long believed to be a separate species. On the Cape Verde Islands, the subspecies madens is endangered, with only six to eight pairs surviving.

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• 3. The Stoop

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  An adult peregrine measures 34-58 cm in length and spans 74-120 cm across its wings. Females can be up to 30% larger than males, a common pattern among bird-eating raptors. The back and long pointed wings are slate grey to bluish black, while the underparts range from white to rusty with thin dark bars. A black cap and a black cheek moustache contrast with a white throat. Young birds are browner and have streaked rather than barred undersides.

  A 2021 study of photographs from around the world examined the malar stripe, the black patch of feathers below each eye. It found the stripe is larger where sunlight is stronger, and concluded that it cuts glare and sharpens vision. The upper beak carries a notch near its tip. This lets a falcon kill by severing the spinal column of its prey at the neck.

  The stoop is the peregrine's hunting dive. The falcon climbs to a great height and then plunges steeply at very high speed, striking in a way that spares itself injury. Air pressure at such speeds could damage a bird's lungs. Small bony tubercles in the nostrils are theorized to steer the airflow away, so the bird can keep breathing. Third eyelids, called nictitating membranes, spread tears across the eyes and clear debris without blocking vision.

  A study of an ideal falcon found a theoretical speed limit of 400 km/h in low-altitude flight and 625 km/h at high altitude. In 2018, researchers at the University of Groningen in the Netherlands and at Oxford University used 3D computer simulations. They showed that high speed also gives the falcon better maneuverability and precision in a strike. The eyes keep pace with the dive. Peregrines have a flicker fusion frequency of 129 Hz, very fast for a bird of their size and far faster than any mammal.

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• 4. Hunting Range

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  Between 1,500 and 2,000 bird species, roughly a fifth of all birds in the world, are hunted by peregrines somewhere. In North America alone the falcon takes more than 300 species, including nearly 100 shorebirds, the widest list of any raptor there. Prey runs from 3 g hummingbirds to the 3.1 kg sandhill crane. Most of what it takes weighs between 20 g and 1100 g.

  In cities, rock doves, the feral pigeons, make up 80% or more of a peregrine's diet. Starlings, swifts, mourning doves and corvids such as magpies, jays and crows fill out the menu. Coastal birds of the large subspecies pealei feed almost entirely on seabirds. In the Brazilian mangrove swamp of Cubatao, a wintering falcon of the subspecies tundrius was seen successfully hunting a juvenile scarlet ibis.

  At night, bats are the mammals most often taken by peregrines. At Rankin Inlet, falcons mostly catch northern collared lemmings, along with a few Arctic ground squirrels. Rabbits, young hares, shrews, mice, voles and squirrels are taken less often. Remains of red fox kits and of an adult female American marten have been found among prey leftovers. Insects, small snakes, lizards and even salmonid fish make up a small share.

  Peregrines hunt most often at dawn and dusk, working over open water, marshes, valleys, fields and tundra. They search from a high perch or from the air. After spotting prey, the falcon folds its wings and tail, tucks its feet, and drops into its stoop. It usually strikes with a clenched foot, stunning or killing the bird in mid-air, then wheels around to catch it. Prey too heavy to carry is dropped to the ground and eaten there. If the first strike misses, the chase continues in a twisting flight.

  Several reported cases of contour-hunting show the falcon using the lie of the land to ambush prey on the ground. In rare cases it has even chased prey on foot. Peregrines have also been documented taking chicks from the nests of birds such as kittiwakes. They pluck their prey before eating it. A 2016 study found that the falcon's presence helps species it does not prefer, while causing a decline in its favoured prey.

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• 5. Nesting Life

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  Nesting pairs are usually more than 1 km apart, and often much farther, which keeps enough food available for each pair and its chicks. A pair may keep several ledges within one territory, using anywhere from one or two up to seven over a 16-year period.

  Peregrines reach sexual maturity between one and three years of age, though in larger populations breeding starts at two to three. A pair mates for life and returns to the same nesting spot each year. The courtship flight mixes acrobatics, tight spirals and steep dives. The male passes prey he has caught to the female in mid-air, and she flies upside down so she can take it from his talons.

  The female picks the site and scrapes a shallow hollow in loose soil, sand, gravel or dead vegetation. She adds no nest materials. Cliff sites usually sit under an overhang, and south-facing ledges are favoured. In parts of Australia and on the west coast of northern North America, large tree hollows serve instead. Before most European peregrines disappeared, a large population in central and western Europe used the abandoned nests of other big birds.

  In the Northern Hemisphere, eggs are usually laid from February to March, and in the Southern Hemisphere from July to August. The Australian subspecies macropus may breed as late as November, and equatorial populations may nest anytime between June and December. A clutch is generally three to four eggs, with extremes of one and five. Incubation lasts 29-33 days, with the female alone sitting at night and the male helping by day. A nest holds an average of 2.5 young, but only about 1.5 fledge, because of infertile eggs and natural losses.

  Newly hatched chicks wear creamy-white down and have oversized feet. Both parents hunt for them, ranging up to 19-24 km from the nest. Chicks fledge 42-46 days after hatching and stay dependent on their parents for up to two months.

  Pairs defend their site against other peregrines and often against ravens and eagles. The worst threats in North America and Europe are the great horned owl and the Eurasian eagle-owl, which pick off nestlings, fledglings and adults by night. Parents defending a nest have killed golden eagles and bald eagles by ambushing them in a full stoop. When a snowy owl killed a newly fledged peregrine, a stooping parent killed the owl in turn. In Florida, invasive snakes such as Burmese pythons and green anacondas could potentially eat peregrines at some stage of growth.

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• 6. Poison and Return

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  During the 1950s, 1960s and 1970s, organochlorine pesticides, especially DDT, pushed the peregrine toward collapse over much of its range. The chemicals built up in the falcons' fat tissue through biomagnification and lowered the calcium in their eggshells. Thinner shells meant fewer eggs survived to hatching. Their prey also laid thinner-shelled eggs, with black petrels as one example. The species became locally extinct in places such as the southeastern United States and Belgium. An alternative view holds that eastern North American populations vanished through hunting and egg collection.

  In 1978, Canada identified the peregrine as endangered, and in the Yukon that year only a single breeding pair was found. Recovery teams bred falcons in captivity. Chicks were fed through a chute or with a hand puppet shaped like a peregrine's head, so they could not see their human keepers and imprint on them. When old enough, the rearing box was opened so the bird could exercise its wings. Feeding was then reduced, forcing the young falcon to learn to hunt. This process is called hacking back to the wild. Before release, a bird spent some days in a special cage atop a tower or cliff ledge.

  The United States removed the peregrine from its endangered species list on the 25th of August 1999. Falconers had helped, working with The Peregrine Fund and state and federal agencies. Controversy followed over the breeding stock, which included Eurasian subspecies. The eastern population of anatum had gone locally extinct, the Midwest population was nearly gone, and the North American gene pool was small. For those reasons, adding non-native birds was justified as a way to improve genetic diversity.

  Scotland saw territory occupancy and breeding success rise after organochlorines were banned. Uneven recovery there suggests that persecution and other factors still mattered in some areas. Finland's peregrines passed through a population bottleneck in the 1970s, yet their genetic diversity matches that of other populations, which indicates that high dispersal rates preserved it. The RSPB estimated 1,402 breeding pairs in the United Kingdom in 2011. In December 2017, the Committee on the Status of Endangered Wildlife in Canada declared the species no longer at risk.

  Illegal poachers still target peregrine eggs and chicks. For that reason, nest locations without protection are usually kept out of public view.

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• 7. City Falcons

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  The first recorded urban breeding pair in the United Kingdom nested on the Swansea Guildhall in the 1980s. Since then, British peregrines have become increasingly urban, particularly in southern areas where suitable inland cliffs are scarce. Worldwide they nest on cathedrals, skyscraper ledges and tower blocks, structures that closely resemble the cliff ledges they prefer. In India, the shaheen falcon has also nested on cellphone transmission towers.

  Portland, Oregon, hosts ten percent of the state's peregrine nests while covering only about 0.1 percent of its land.

  Artificial illumination also helps city falcons. It lets them keep hunting into dusk, when natural light would otherwise be too low to pursue prey. In the UK this has allowed them to take nocturnal migrants such as redwings, fieldfares, starlings and woodcocks.

  City life carries risks. Falcons that move into urban areas can pick up human-borne pathogens and heavy metals, which can be deadly for chicks. Many urban pairs still draw media attention and are watched by cameras.

  In Southampton in 2013, a nest inside a mobile phone mast held up the restoration of phone service for several months. Vodafone engineers sent to repair a faulty transmitter found the nest. The Wildlife and Countryside Act barred them from proceeding, on pain of a possible prison sentence, until the chicks fledged.

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• 8. Falconry and Symbol

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  Nomads in central Asia began flying peregrines for hunting more than 3,000 years ago. Falconers prize the bird for its athleticism, its eagerness and an even temper that makes it one of the easier falcons to train. It naturally circles above the falconer, a behavior called waiting on, until game is flushed. Then it dives in a stoop and delivers a knockout blow with a clenched talon, even to game much larger than itself. Because the subspecies vary so widely in size, one exists for almost any size and type of game bird.

  During World War II, peregrines were used to intercept homing pigeons. Today falconers fly them to scare birds away from airports and lower the risk of bird strikes on aircraft. Captive breeding now supplies falcons commercially, which mostly removes the need to take wild birds. Until 2004, nearly all peregrines used in American falconry were captive-bred from birds taken before the US Endangered Species Act. In 2004, after years of work with the US Fish and Wildlife Service, a limited take of wild peregrines was allowed, the first for falconry in over 30 years.

  Breeders also cross peregrines with other falcons. A peregrine-gyrfalcon hybrid joins the gyrfalcon's size, strength and horizontal speed with the peregrine's instinct to stoop and its tolerance of warm weather. Many consider it ideal for larger game such as sage-grouse. Pairing a peregrine with the lanner falcon, Falco biarmicus, produces the perilanner, which blends peregrine hunting skill with lanner hardiness.

  The Ancient Egyptian sun god Ra was often shown as a man with a falcon's head and a solar disk. Most Egyptologists think the bird was probably a lanner. The Mississippian culture, between about 800 and 1500, used peregrine imagery as a symbol of aerial, celestial power. In the late Middle Ages, Western European nobles linked the peregrine with princes, just below the gyrfalcon, which was linked with kings. One description called it "a royal bird, more armed by its courage than its claws". Bowling Green State University in Ohio has used the peregrine as its mascot since 1927. The 2007 Idaho state quarter features one, and Chicago has named it the official city bird.

  J. A. Baker's book The Peregrine records, in diary form, a single winter from October to April near his home in Chelmsford, Essex. Mark Cocker regards it as "one of the most outstanding books on nature in the twentieth century". Werner Herzog called it "the one book I would ask you to read if you want to make films". Elsewhere Herzog said "it has prose of the calibre that we have not seen since Joseph Conrad".

  An episode of the television series Starman in 1986, titled Peregrine, followed an injured falcon and the endangered species program. It was filmed with help from the University of California's peregrine falcon project in Santa Cruz. In 1999, Suzuki of Japan named a new motorcycle Hayabusa, the Japanese word for peregrine falcon. The company claimed its top model was the fastest production motorcycle in the world at the time.

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