Falco rusticolus Linnaeus, 1758, Sweden. Monotypic (no subspecies).
OTHER COMMON NAMES
English: Gyrfalcon; French: Faucon gerfaut; German: Gerfalke; Spanish: Halcуn Gerifalte.
Male 18.9–24.0 in (48–61 cm), female 20.1–25.2 in (51–64 cm); male 1.8–2.9 lb (800–1,325 g), female 2.2–4.6 lb (1,000–2,100 g). Largest of the falconids and the only white falcon. Highly variable plumage: from nearly pure white through various barred, chevroned, and streaked gray plumages to nearly uniform dark gray-brown. Adults have bright yellow legs and feet. Juveniles tend to be slightly browner and more heavily streaked; pale gray legs and feet. White form usual in high Arctic; dark form in Labrador; gray forms predominate in Iceland; mostly gray individuals grading to equal numbers of white individuals from west to east across Russia and Siberia.
The most northern of all diurnal raptors. Breeds around the Arctic circle: Iceland, Greenland, North America, and Eurasia; winters farther south.
Fairly uniform habitat: tundra and taiga, from sea level to about 4,600 ft (1,400 m), ice bound and snow covered much of the year. Favors rivers and seacoasts, also mountains. Winter migrant to ice edge, farmland, agricultural land, and steppe.
In populations below 70° north many birds are resident, especially adult males. Migratory above 70° north, moves mainly but not only south to over-winter in warmer areas where prey is plentiful, mostly north of 40° north. Juvenile tracked with satellite transmitter from Alaska to Russia and back.
FEEDING ECOLOGY AND DIET
Hunts mostly ground-dwelling birds and mammals, such as ptarmigan, grouse, ground squirrels, and lemmings. Mostly flies low and fast to surprise and flush prey; occasionally takes birds after pursuit on the wing, and lifts waterfowl and shorebirds from water.
Breeds annually as solitary pairs from March to July. Lays eggs in depression on cliff ledge, large stick nest of another species, or man-made structure. High variation in clutch size and nesting success, depending on prey availability; clutch usually three and color varies according to subspecies: largest is Peale’s falcon (F. p. pealei) of coastal North America and the Aleutian Islands; smallest are desert forms of Eurasia and Africa. A handsome, powerful falcon with pointed wings, a rather short tail and a black-helmeted head. Upperparts blue-black to charcoal; underparts white to rufous with black broken bars. Juveniles (first year) are browner, with streaking to underparts. Subspecies tend to be darkest in humid areas, palest in deserts.
Perhaps the widest breeding
of any bird. Almost worldwide, on all continents except the Antarctic and many oceanic islands (such as Fiji); notably absent from the high Arctic (Iceland, Newfoundland) and New Zealand.
Among the most variable of all birds, from the hot tropics to cold coasts and islands, dry deserts and rugged cliff lines to forest and flat treeless tundra, from sea level to about 13,000 ft (4,000 m).
Many Northern hemisphere populations are long-distance migrants, moving south for the winter, stopping to rest and eat en route, with the most northern birds often travelling farthest south (for example, from Greenland to extreme southern South America). In Southern hemisphere and at mid-latitudes, adults are mainly resident year round.
FEEDING ECOLOGY AND DIET
A specialist hunter of birds caught in flight. Attacks from a perch or the air, sometimes in a spectacular stoop at great speed to strike prey in mid-air, less often on the ground or in water. Favors flock species, particularly pigeons and doves, or four but up to seven; incubation 33–36 days; fledges at about seven weeks.
Not threatened. Naturally uncommon but can be locally common. Its preference for remote habitat gives it some protection from threats to many other raptors. Fur trappers in Arctic Russia may kill 1,000–2,000 annually, some are taken by egg collectors and falconers.
SIGNIFICANCE TO HUMANS
Prized for falconry, but probably small numbers taken from wild and are now bred in captivity for that purpose.
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