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 (186
0–1954).
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.
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Mythical Falcons
Detective Tom Polhaus (picks up falcon statue): Heavy. What is it?
Sam Spade: The, uh, stuff that dreams are made of.
Polhaus: Huh?
(closing lines of The Maltese Falcon, 1941)
ON A FOGGY NOVEMBER dawn in 1941, the American bird-preservationist Rosalie Edge was woken by the frantic alarm-calls of city birds. She peered from her Manhattan window into Central Park. What had caused this commotion? Blinking back sleep, she realized that the stone falcon she could see carved from a rocky outcrop was no statue. It was alive. Suddenly, time stood still. She was transfixed. My soul, she wrote, ‘drank in the sight’ of this impossibly exotic visitor to the modern world. Was it, she breathed, the ghost of Hathor, wandered from the Metropolitan Museum and overtaken by sunrise? But no: ‘time resumed as the swift-winged falcon swept into the air . . . the enchantment was broken’.1
Another ancient falcon worked its enchantments on Humphrey Bogart, Peter Lorre, Sydney Greenstreet and audiences across America that year. The small black statuette of The Maltese Falcon casts its dark shadow across the screen at the very beginning of John Huston’s film noir, and the audience reads the barest bones of its history in scrolling text:
In 1539, the Knights Templar of Malta paid tribute to Charles V of Spain by sending him a Golden Falcon encrusted from beak to claw with rarest jewels . . . but pirates seized the galley carrying this priceless token and the fate of the Maltese Falcon remains a mystery to this day.
While driving the plot, the Maltese Falcon remains a mystery. Although it reveals the characters of the people in the film – all of whom desire or fear it – and the worlds in which they live, it is a mute object that reveals nothing more about itself. Likewise, that Central Park encounter at dawn tells us almost nothing about peregrines. But it tells us much about the writer herself and about the era she lived in, revealing some intriguing contemporary attitudes towards nature and history. In wartime America, it seems, falcons could be viewed as mystical manifestations of an age of theriomorphic gods and ancient ritual. But falcons carried many other meanings, too. Falcon-enthusiasts such as Edge saw them as living fragments of primeval wilderness imperilled by the relentless encroachment of modernity. Writing about falcons in this period is commonly shot through with a gloomy romanticism akin to that displayed in the works of many contemporary anthropologists who saw the cultures they studied as exotic, primitive, vital and ultimately doomed by historical progress.
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Bogey and the black bird: Humphrey Bogart, the Maltese Falcon and their conjoined shadow in a publicity shot for John Huston’s 1941 film.
Falcon Page 3
