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Natural History

THE 60-ODD SPECIES of the falcon family Falconidae superficially resemble but are probably only distantly related to the other diurnal birds of prey such as hawks, eagles and vultures; some researchers think they are more closely related to owls. They are very variable in shape and habit. From the garbage-can-raiding, raucous, vulture-like caracaras to the secretive tropical forest falcons, all share certain features, such as a bony tubercle in the nostril and a unique moult pattern, which mark them as members of this family. And taxonomically nested within the Falconidae are the ‘true falcons’ of the genus Falco. These species are thought to have evolved relatively recently, perhaps seven or eight million years ago when climatic changes opened up millions of acres of new savannah and steppe grassland. A rapid, explosive radiation of forms occurred to take advantage of these open landscapes.

Falco is often subdivided into four groups: the largely insectivorous hobbies, the tiny, bird-killing merlins, the kestrels, and the group with which we are directly concerned, the large falcons, which can be further divided into two groups, the peregrines and the desert falcons. Both are fast-flying, dark-eyed, active hunters of open airspace. The peregrines specialize in avian prey, while the desert falcons also take mammals, reptiles and insects. In common with many bird-catching raptors, both groups show reversed size dimorphism (RSD): that is, females are considerably larger than males. Evolutionary ecologists have been trying to account for this for years. Perhaps females prefer smaller males because they present less of a threat to themselves and their young. Or perhaps aggressive female competition for males who hold the best breeding territories has selected for large females. Another theory sees RSD as allowing the exploitation of a wider range of prey – with males specializing in catching smaller, more agile birds and females in catching larger, less manoeuvrable ones – but this does not explain why females, rather than males, should be the larger of the two. Tiercel, the falconry term for a male falcon, is from the Old French terçuel, derived from the Latin tertius meaning a third; males are generally about a third smaller than females.

A young peregrine in flight, showing the long-pointed wings and dark cheek markings so typical of the genus Falco.

Portrait of an adult peregrine falcon. This wild female is looking through an office window in Toronto, Canada.

Western science counts around ten species in this large falcon group, but exactly how they are related and whether particular forms should be considered full species, subspecies or mere races of other species is a scientific conundrum. Such confusion is not helped by the discovery that captive-bred hybrids between some species, such as gyrfalcons and saker falcons, are fully fertile. What is the point of worrying about precise definitions of species, one might ask; falcons existed for millions of years before we started fretting about how to classify them. But these taxonomic decisions have real-world implications. Conservation requires stable definitions of the things we are trying to conserve; species or other units must be legally defined. Many falcon populations are threatened by loss of habitat or by direct persecution, but these population types may ‘fall through the net’ of Western taxonomy, as in the case of the saker falcon, a species in which the non-coincidence of scientific and folk taxonomies is distinctly problematic. Western science describes two to five subspecies of the saker. Arab falconers, however, use a complex taxonomy based on size, colour and conformation, such as ashgar (white), aukthar (green), jerudi (barred), hurr shami (red), and so on. In post-Soviet Russia, illegal smuggling of particularly favoured colour forms for the Arab falcon market exerts disproportionate pressure on populations that cannot be granted greater legal protection than others because they remain outside the scientific categories of Western conservation.

Young peregrine falcons have streaked underparts, as seen in this early 19th-century Indian watercolour in the Tanjore style.

THE PEREGRINES

The peregrine, wrote W. Kenneth Richmond, is a bird of ‘perfect proportions and finely cut features, daring and intelligence, spectacular performance in the air and matchless execution in the chase – it has them all, a natural aristocrat’.1 Here the falcon sounds more like a John Buchan hero or a Second World War flying ace, but the effusive fashioning of this falcon into the discourse of nobility has a long heritage. In Iran and Arabia, the peregrine is called Shaheen, Farsi for ‘emperor’. Pero López de Ayala, Chancellor of Castile and medieval Spanish authority on falconry, thought it ‘the noblest and best of the birds of prey, the lord and prince of hunting birds’.² And 700 years later the American ornithologist Dean Amadon rather oddly conflated concepts of adaptative fitness with sheer admiration when he called it the finest of falcons and assumed it must therefore be the most highly evolved of the Falco group. The name ‘peregrine’ comes from the Latin peregrinus ‘wanderer’; if we assume the mantle of a geopolitician, and measure success by the extent of territory held, Falco peregrinus is the most successful bird alive. Except for Antarctica, Iceland and some oceanic islands, the species is found on every continent and in a huge variety of forms. These range in colour from the pallid, white-fronted morph of the Chilean peregrine F. p. cassini to the dark Madagascar peregrine F. p. radama. Peregrines from humid, tropical latitudes tend to be darker and more richly coloured than those from arid or northerly regions. Desert peregrine types include the tiny blue and rust-coloured broad-shouldered Barbary falcon F. pelegrinoides from North Africa, and in the mountains of Iran and Afghanistan, the red-naped shaheen F. p. babylonicus. In Iran this bird is called the Shaheen-e kuhi, the shaheen of the hills, as opposed to the Shaheen-e bahri, the shaheen of the sea, the migratory Arctic peregrine that winters on the Iranian coasts.

THE DESERT FALCONS

The largest falcon, and arguably the most impressive, is a member of a softer-plumaged subgroup of Falco known familiarly as the desert falcons, for these species generally inhabit arid regions. The gyrfalcon Falco rusticolus is a hulking great bird; females are nearly the size of a small eagle. Gyrs live in the arctic and subarctic where prey can be scarce and water is locked into ice for much of the year; they are well adapted for the exigencies of this habitat, with thick, deep plumage and shaggy lower-breast feathers that entirely cover their feet when they sit; they will bathe with relish in freshly thawed snow. They hunt mainly ptarmigan, lemmings and Arctic hares, but they will eat fish and scavenge from frozen carcasses.

A grey-phase gyrfalcon tail-feather.

A white gyrfalcon attacking a tundra swan. Scroll painting on silk by Yin Xie, Ming period.

Gyrs have a number of colour-phases broadly correlated with their geographic origin. The obsoletus birds of boreal North America are almost black. Grey and silver forms are found throughout their range. From northern Greenland and Kamchatka come brilliant white birds with black-barred scapulars and wing feathers, called candicans. In seventeenth-century Spain these birds were called Letrados because the marks on their backs looked like the marks of a pen. The gyrfalcon’s size and beauty have granted it high status in all falconry cultures; in medieval Europe it was particularly favoured for flights at large quarry such as the red kite (Milvus milvus) and crane (Grus grus).

Today gyrs are occasionally given as gifts to Gulf States dignitaries by governments and oil companies, but from the eleventh century until the eighteenth they were among the most valuable of diplomatic gifts. In 1236 Edward I of England received eight grey and three white gyrfalcons from Norway. He immediately sent four of the grey gyrs to the king of Castile, apologizing that he could not send white falcons, for only recently he had lost nine of his own. And they were frequently used in diplomatic negotiations. Charles VI of France sent Norwegian gyrfalcons to Bajazet as a ransom for the marshals de Boucicault and de la Tremoille after the battle of Nikopol in 1396, while the Duke of Burgundy brought about the liberation of his son, the Duke of Nevers, by sending his Turkish captors twelve white gyrfalcons. In the 1930s Hermann Goering planned to release white gyrs in the German Alps. He was convinced that this, the largest and most powerful of falcons, must have had its ancestral home in Germany. The ideological underpinnings of this ecological introduction are, to say the least, uncomfortable, and Renz Waller’s portrait of Goering’s own white gyrfalcon bathed in mountain sunlight is disturbingly true to the artistic conventions of National Socialist portraiture.

Hermann Goering’s white gyrfalcon, in an oil by falconer-artist Renz Waller.

The saker falcon, the traditional species of Arab falconry.

A 19th-century lithograph by Joseph Wolf of lanner falcons: an adult in front, an immature bird (eating a quail) behind.

Another desert falcon, the saker falcon Falco cherrug, is the traditional bird of Arab falconry. Trapped in the autumn on migration across Arabia to wintering grounds in East Africa, the bird was known to Bedouin falconers simply as saqur ‘falcon’. Sakers nest in steppe grassland and in open forests from eastern Europe across Asia. Like the gyr, they occur in a wide variety of forms. Plain-backed, brown, Western lowland birds become larger, more rufous in colour and barred in the Eastern highland forms. But this clinal distribution is only a broad trend; saker populations include spotted or barred, brown, grey, burnt orange, almost black birds and birds bleached by the sun to near white. The Altai falcon Falco altaicus is a dark gyr-like bird from the Russian Altai, known as Turul in Mongolia. In India and Pakistan the desert falcons are represented by the laggar falcon Falco jugger, a soft-plumaged brown and cream falcon that preys on lizards as well as birds and small mammals. In the arid and semi-arid regions of Africa and southern Europe, its counterpart is the steel-blue and salmon-pink lanner falcon, Falco biarmicus. An avian specialist, the lanner often ambushes desert birds at waterholes and is renowned in falconry for its pleasant temperament. The sixteenth-century falconer Edmund Bert boasted that his trained goshawks were as ‘sociable and familiar as a lanner’.3 Conversely, the North American prairie falcon Falco mexicanus is a celebrated malcontent in falconry, known for its foul temper. It inhabits the plains and deserts of the American West. Although it bears a superficial resemblance to the saker falcon and is traditionally assigned to the desert falcon group, recent genetic studies have suggested that the species is more closely related to the peregrine.

A New Zealand falcon on South Island. The only falcon species native to New Zealand, it is threatened by habitat destruction and by the nest-raids of introduced possums.

Australasia is home to a number of large falcons hard to assign to either desert falcon or peregrine category, such as the black falcon F. subniger and grey falcon F. hypoleucos. Other Australasian falcons have evolved to exploit predatory niches elsewhere filled by hawks and buzzards, the hawk-shaped New Zealand falcon F. novaseelandiae, in particular. Along with a few other large falcon species, these appear less often in this book because their cultural history is less rich than the species previously discussed, either because their relationship with indigenous communities is lamentably undocumented or because they have little contact with humans at all. For example, the richly coloured, huge-footed, orange-breasted falcon F. deiroleucos is a species whose mysteriousness is, in part, a function of biologists’ difficulty in finding it in its remote South American forest habitat.

WHAT IS IT LIKE TO BE A FALCON?

Claiming to understand the life-world of another person is philosophically suspect; for a different animal, the attempt is perhaps absurd – but undeniably fascinating. Our commonsense anthropomorphism suggests that the world the falcon experiences is probably rather like ours, only more acutely perceived. But from the available evidence it seems that the falcon’s sensory world is as different from ours as is that of a bat or a bumblebee. Their high-speed sensory and nervous systems give them extremely fast reactions. Their world moves about ten times faster than ours, so events in time that we perceive as a blur, like a dragonfly zipping past our eyes, are much slower to them. Our brains cannot see more than 20 events per second – falcons see 70–80; they are unable to recognize the 25-pictures-per-second moving image on a television screen. Seeing things closer together in time than we do allows them to stretch out a foot at full speed to grab a bird or a dragonfly from the air.

The morphology of the peregrine falcon, by Joseph Wolf. Note the tomial tooth on the beak, used to break the neck of prey.

When fixing their eyes on an object, falcons characteristically bob their head up and down several times. In so doing they are triangulating the object, using motion parallax to ascertain distance. Their visual acuity is astonishing. A kestrel can resolve a 2-millimetre insect at 18 metres away. How is this possible? Partly through the size of the eyes: these are so huge that the back of each orb presses into the other in the middle of the skull. The retina is avascularized to prevent shadows or light-scattering; instead of blood vessels, nutrients are supplied to the retinal cells from a projecting, pleated structure called the pectin. Falcons’ visual sensory cells, the rods and cones, are far more densely packed than ours, particularly the colour-sensitive cones. While we have around 30,000 cones in the most sensitive part of the retina, the fovea, raptors have around 1 million. Moreover, each of their photoreceptive cells has individual representation in the brain. Associated with the cone cells are coloured oil droplets that are thought to sharpen contrast and pierce haze, or may protect those cells from ultraviolet radiation. While humans have one fovea, falcons have two – thus, two images of a single object focused on these foveae may fuse in the brain and produce a true stereoscopic image. Furthermore, between these two foveae, there is a horizontal streak of increased sensitivity, a kind of ‘smeared fovea’ running between them. This allows falcons to scan the horizon without moving their heads. But not only do falcons see more clearly than humans, they also see things differently. They are believed to see polarized light, useful for navigating in cloudy skies. They also see ultraviolet. Overall, falcons have a radically different phenomenal world. Humans have three different receptor-sensitivities – red, green and blue; everything we see is built from these three colours. Falcons, like other birds, have four. We have three-dimensional colour vision; they have four. It is hard to comprehend. Dr Andy Bennett, researcher in the field of avian vision, considers the difference between human and bird vision as being of the same order as that between black-and-white and colour television. In the barest of functional terms, a falcon is a pair of eyes set in a well-armed, perfectly engineered airframe.

The beak is extremely powerful; anyone who has been bitten by a falcon will vigorously attest to this. A sharp projection on the upper mandible fits neatly into a notch in the bottom mandible. This ‘tomial tooth’ is used to sever the vertebrae of prey, an efficient method of administering the coup de grâce to avoid a tussle on the ground and broken feathers. Beak dimensions vary between species and sexes. Southern latitude peregrines have proportionately more massive beaks than northern birds. Once thought to be an adaptation for killing dangerous prey such as parrots, the reasons for this gradient are obscure. There is, however, a strong correlation between foot shape and prey type. Bird-killing species such as the peregrine and lanner have relatively short legs to withstand the impact of hitting prey at speed; their toes are long and thin. On the underside of each toe are warty pads of skin that fit closely against the curve of the talon when the foot is clenched, giving the bird secure purchase on feathers. Sakers and gyrs have proportionately thicker, shorter toes and longer legs, a better arrangement for catching mammalian prey in snow, grass or steppe scrub. The toes have a ‘ratchet’ tendon mechanism: after the initial effort of clenching the foot, falcons can hold them locked shut with no muscular effort, an invaluable strategy for carrying prey in flight or sleeping on a branch in high winds. At rest, falcons habitually tuck one foot up underneath their feathers. There, it is often invisible. Visitors to falconry centres often ask staff why they have so many one-footed falcons.

The skeleton is light, strong and highly adapted for the demands of flight. Some bones are fused. Major bones are hollow, air-filled and reinforced by bone struts. These pneumatized bones are connected to the bird’s respiratory system. Really connected: a bird suffering a compound fracture of a wing or leg can breathe through the exposed end of the bone. The massive flight muscles, making up around 20 per cent of the weight of a peregrine, are attached to the sternum, or ‘keel’, and are served by oxygen from a highly efficient respiratory system. Rather than an in–out lung system like ours, air is drawn continuously and in one direction through the lungs via a series of nine thin-walled air sacs throughout the body; these also have a thermo-regulatory function. Overall, falcons’ respiratory and circulatory systems are far more efficient than ours; despite the far greater metabolic rate of falcons, they breathe at about the same rate we do.

Peregrine falcon skeleton.

Compared with other birds, a falcon’s digestive system is short, for flesh is easily digested. Falcons cannot digest feathers and fur; these are stored in the crop and ejected from the mouth in the form of a tightly packed ‘casting’ some hours later. They drink infrequently, for most of the moisture they require is derived from their prey and their water economy is impressive; falcon faeces – ‘mutes’ or ‘hawk chalk’ in falconers’ parlance – are composed of faecal matter and a chalky suspension of uric acid crystals. Falcons can excrete uric acid 3,000 times more concentrated than their blood levels. That’s acidic enough to etch steel.

FLIGHT

What of flight, the single most celebrated falcon characteristic? Falcon bodies are heavy in relation to their wing area. Their flight profile is unstable and anhedral – that is, ‘^’-shaped, the opposite of the ‘v’-shaped dihedral attitude of soaring vultures and eagles. Their wings have a high aspect ratio – the ratio between wingspan and wing width – and their low-camber wings are long and pointed. The result is a low-drag conformation more suited to active, flapping flight and fast gliding than soaring. But falcons gain height by powering up on beating wings, or by soaring in rising thermals or updrafts from cliffs or hills. From high perches or from altitudes that may be so high they are invisible from the ground, falcons stoop, or dive, upon prey. Falcon hunting tactics are to be found codified in fighter pilot tactical manuals of the First and Second World Wars – there are only a few places to hide in the sky. Falcons often attack from above by diving out of the sun; Royal Air Force fighter squadrons would assume positions above enemy aircraft formations in order to do the same. Falcons often use the blind spot of their target to approach unnoticed from behind and beneath and fly their target down. Similarly, RAF ‘fighter area tactics’ in the Battle of France called for fighter sections to fly into the blind spot of lone bombers, 2,400 feet behind, 100–200 feet below, before attacking. To approach ground prey falcons glide fast, wings motionless, to present a minimal head-on profile. Sometimes they deceive, imitating the flight style of harmless birds in order to approach unsuspecting prey. Once overtaken, prey is either grabbed in midair or hit hard with one or both feet. At the speeds attained by stooping falcons, this clout often kills the prey outright.

Long-distance migrant falcons tend to have narrower, longer wings than those of sedentary populations. Here a dark-phase saker flies through a mountain pass in northern Pakistan.

Falcons living in more enclosed habitats have lower aspect-ratio wings and longer tails, a flight conformation suited for rapid turns in a world of obstacles. This is particularly apparent in the New Zealand falcon, which exploits an ecological niche filled elsewhere by hawks. This aberrant falcon follows prey into trees and even stalks prey on foot through undergrowth. Immature falcons also have longer tails and broader wings than adults, a conformation suited to hunting methods amenable to inexperienced birds: young sakers, for example, will ‘quarter’ or hover over rodent-rich grassland. After their first moult, their tails shorten and their wings grow narrower, their feathers stiffer and stronger.

Wing silhouettes of four falcon species. Narrower, longer wings are more suited to aerial attack; broader, rounder wings also allow slow searching flight.

Falcon flight is fast and structurally stressful. Straight-line low-level fast flight in gyrfalcons has been put at 80 mph, but diving peregrines reach well over twice this speed. The bony tubercle in falcon nostrils is often presumed to aid breathing at these high speeds, but it may indicate airspeed by sensing temperature or pressure changes produced by different external air-stream velocities. An extra pair of bones at the base of the tail gives increased surface area for attaching the powerful depressor muscles of the tail – essential for turning and braking sharply in pursuit flights. Such turns exert phenomenal stresses on the bird. The biometrician Vance Tucker attached a miniature accelerometer to trained falcons to record the G-forces experienced when pulling up near vertically from the bottom of steep dives. As blood drains from their eyes and brains, human pilots may experience total loss of consciousness – G-LOC – pulling around 6 GS. Eyewitness reports of Tucker’s experiments enthuse about how his accelerometer went ‘off scale’ as the falcons pulled over 25 GS. At this G-loading, a 2 lb falcon weighs over 60 lb.

Vultures and other slow-soaring fliers have rough, loose body feathers and highly emarginated, splayed primary wing feathers that function as miniature aerofoils to permit low airspeeds. Falcon feathers, however, are tightly contoured; they mould the bird into a sleek shape offering little air resistance. Moulted and replaced once a year, they are of several types: long, stiff attenuated flight feathers; insulating down feathers; contour feathers that cover and smooth the body; bristly crines around the beak and cere that shed dried blood after a meal; and barely visible long, hairlike filoplumes. These are associated with the flight feathers, and are well served at their bases by nerve endings. Their sensory input is thought to monitor the flow of air over the wing surfaces to allow precise adjustments of wing shape in flight.

Much of a falcon’s time is taken up with feather-maintenance; they preen for long periods and bathe frequently. Gently nibbling the uropygial gland just above the tail, preening falcons pick up a fluid of fatty acids, fat and wax and spread it onto their feathers; in addition to waterproofing them, the fluid contains a vitamin precursor that sunlight converts to vitamin D; this is picked up and ingested in the next preening session. As to plumage colour, black, brown, grey, orange and white are typical falcon tones. Lanners, some saker races and most of the peregrine group have bluish upper parts. This blue colouration is common in bird-killing raptors of other species, but no one knows why this should be the case. A characteristic falcon marking is the dark malar stripe that runs down from beneath the eye. In some species it is so extensive that the falcon appears hooded; in a very few, it may be faint or even absent. The stripe appears to combat glare, functionally akin to the dark make-up American footballers wear beneath their eyes. And the bare skin around their eyes and on their legs and cere varies from pale blue or grey to bright orange. These bright colours may be involved in display and mate choice, for immature falcons are far less brightly coloured on their bare parts. First-year falcons also have streaked rather than barred undersides and are browner or paler than adults. The barred and contrast-rich plumage of adults may be associated with territorial signalling, while dull-coloured juvenile plumage allows young birds to wander relatively unpressed through adult territories in the post-fledging and dispersal period.

MIGRATION

Falcon movements can be epic. Acres of text have been written on the whys and wherefores of bird migration. Recent studies indicate that a strong genetic component is involved in the development of migratory behaviour in birds, but an external reason is often straightforwardly apparent for falcon migrations: food. In Kyrgyzstan, sakers move down from the Tien Shan mountains with the first snowfalls in late summer, following their prey to the plains below. Rocky Mountain prairie falcons move to higher altitudes in summer because their main prey at lower levels, Townsend’s ground squirrel, hides underground to escape the baking heat. Nomadic movements in response to unpredictable food resources are also found in falcons living in arid zones, such as lanners. Falcons breeding in the arctic migrate thousands of miles each spring and autumn, ‘leapfrogging’ over resident or partial-migrant birds from mid-latitude populations who live in areas with year-round food. Greenland-nesting peregrines winter as far south as Peru; Siberian peregrines move down to Afghanistan, Pakistan, and as far as South Africa.

Conversely, falcons living in regions where prey is available year-round tend to be sedentary. City peregrines in Manhattan have a year-round source of pigeon food. Peregrines in Britain may use man-made food sources in areas where wild prey is scarce in winter; populations on northern moors have taken advantage of the traditional flight-lines of racing pigeons, much to the dismay of the pigeon-racing community. Peregrines on the humid Queen Charlotte Islands in British Columbia subsist on seabirds; black shaheens in bird-rich tropical Sri Lanka remain at their breeding territories all year.

Migrating falcons move fast, sometimes hundreds of miles a day across land or ocean. One of the copies of De arte venandi cum avibus, Frederick II’s thirteenth-century magnum opus, has an illustration of a peregrine sitting on the rigging of a ship, and gyrfalcons and peregrines still land on ships during migration. On a transatlantic crossing in the 1930s the American biologist-falconer Captain Luff Meredith could hardly believe his luck when he was suddenly presented with a beautiful white gyrfalcon: landing on deck mid-crossing, it had been promptly captured by the crew. Meredith’s celebrity falconry status prompted the famous fan dancer Sally Rand to visit him and demand a falcon for her act. Apparently her request was declined.

A falcon resting on a ship, from Frederick II of Hohenstaufen’s 13th-century De arte venandi cum avibus. Migrating falcons still perch on ships.

Clearly, ships are not optimal falcon habitats. But the genus Falco is not tied to particular landscapes; that characteristic falcon silhouette can be seen over city centres, deserts and arctic ice-cliffs and in the humid air above tropical forests. The large falcons tend to be solitary animals outside the breeding season, although pairs of some species such as lanners hunt cooperatively all year. Lanner falcons in arid regions also congregate in groups at waterholes where prey is concentrated, or may assemble in loose flocks to feed on termite swarms.

BREEDING

Falcons time their breeding to coincide with maximum prey abundance; young falcons are reared and fledge when there is plenty of inexperienced juvenile prey to catch. Most temperate-zone and high-latitude falcons return from their winter territories to their breeding territories early in the year, pair up and lay their eggs in spring. Their breeding territory is generally much larger than the winter territory of single birds, for far more prey is required to feed a family. Its size varies in relation to the availability of prey in the surrounding environment; the breeding territory of the prairie falcon, for example, may be as few as 30 or as many as 400 square kilometres.

A peregrine falcon drives a raven from its nesting territory in this engraving by the renowned bird and sporting artist George Lodge (1860–1954).

This territory may contain several alternate nest sites used from year to year; bare ‘scrapes’ on ledges, in cliff potholes or on river cutbanks; or the reused nests of other large birds, such as ravens and eagles. Falcons do not build their own nests. Some peregrine populations nest in trees; one now-extinct population relied on the hollow tops of dead old-growth forest trees in Tennessee. Traditional nest sites can be ancient: gyr eyries in Greenland may go back thousands of years. The Karok people of north-west California considered the peregrine, which they called Aikneich or Aikiren, to be immortal, for a pair had nested at the summit of A’u’ich (Sugarloaf Mountain) since time immemorial. Some British peregrine eyries have been recorded as occupied since the twelfth century, and some, like those of Lundy Island, produced young celebrated for their prowess as falconry birds. There may be some truth underlying such tales of ‘special’ eyries. Young falcons tend to return to the area where they were reared. This high degree of philopatry may contribute to speciation in the genus, with local genetic traits reinforced over many years.

High nesting densities of otherwise territorial raptors can occur when prey is abundant but nesting sites unevenly concentrated. On the gorges of the Snake River in Idaho, for example, some kilometres from the gorge made famous by Evel Knievel’s failed attempt to jump it on a jet cycle, approximately one pair of prairie falcons nests per 0.65 km. These pairs hunt the numerous ground squirrels in the sagebrush desert that extends out from the river gorge. In steppe and prairie grasslands a lack of nest sites may limit falcon populations, even though prey populations may be high enough to support numerous pairs. Conservation management techniques involving the erection of artificial nesting platforms have proved successful in some cases, but some falcons require no such habitat augmentation. Saker falcon ground nests have been found in Mongolia, and there are large populations of ground nesting peregrines in the Arctic. Ground nesting is a dangerous game, exposing eggs and young to predators, and mutualistic relationships with other species have developed. On the Taymyr Peninsula in Siberia otherwise vulnerable ground-nesting peregrine eyries are found in statistically significant proximity to red-breasted goose Branta ruficollis colonies. If the vigilant geese spot arctic foxes, or avian predators, their alarm call alerts the falcons, whose aggressive dives to drive away the threat benefit both peregrines and geese.

Falcons don’t build nests; some species lay their eggs on ledges, while others often use old buzzard or raven nests, like this saker in Mongolia.

Large falcons generally breed in their second year or later, but there are numbers of non-breeding adults in the population at any one time. Gyrfalcons may not breed at all in years when lemmings or ptarmigan are scarce. Falcons are generally monogamous; extra-pair copulations are infrequent. Falcon courtship is not marked by colourful plumage; instead, males may perform dizzying courtship flights near possible nest sites, sometimes joined by the female. Pair bonding is cemented by males bringing prey to the female and by elegant nest-ledge displays of bowing and calling. Frequent copulations – around two or three an hour before egg laying – further strengthen the pair bond. The single clutch consists of three to five blotched, rusty brown eggs, which are incubated by the female for around a month. The young, or ‘eyasses’, hatch with a thin covering of grey or whitish down that is replaced by a thicker coat a week or so later. Feather growth is rapid, quills breaking through the down as young falcons exercise their wings and their hunting instincts. They are playful in the nest, grabbing sticks, stones and feathers in their feet, turning their heads upside down to watch buzzing flies and distant birds, pulling on the wings and tails of their irritated siblings. They take their first unsteady flights aged around 40 to 50 days, after which the parents teach them the rudiments of aerial hunting strategies by dropping dead or disabled prey from a height for the pursuing young to catch.

Fledgling, or eyass, peregrines, in a well-observed 1895 gouache by the Finnish artist Eero Nicolai Jarnefelt. The leftmost bird is ‘mantling’ protectively over food; the other is calling with the typical hunched posture of a food-begging youngster.

Young falcons begin killing their own prey and disperse from the territory after four to six weeks, after which their mortality is relatively high. Around 60 per cent of young falcons die in their first year, mainly from starvation. This fact is surprising to many commentators who see falcons as the most efficient predators alive. Surprises like this occur when biology doesn’t match mythology – that is, when real animals don’t match the ways humans perceive them. Bedouin falconers, for example, who only saw migrating falcons in the desert, never breeding pairs, quite reasonably mapped their own gender concepts onto the falcons they trapped: they assumed that the larger, more powerful birds were male and the smaller, female. But scientific understandings of falcons, too, can be strongly inflected or invisibly shaped by our own social preoccupations. And conservation is riven by conflicts arising because animals possess different values for different cultures. Are falcons paradigms of wildness and freedom? Vermin? Sacred objects? A commercially valuable wildlife resource? Or untouchable and charismatic icons of threatened nature? Investigating these different meanings has real-world implications. People conserve animals because they value them, and these valuations are tied to their own social and cultural worlds. The pictures and stories through which falcons are used to articulate and reinforce different cultural understandings of the world are myths, and they are the subject of the next chapter.