The Gyrfalcon has many names and subtle variations; such as the White, or Greenland Gyrfalcon, the Gray Gyrfalcon, MacFarlane's Gyrfalcon, etc. Actually, many of these variations are just Gyrfalcons in different stages of plumage, of which it has 3 (gray, black and white). This information is about the common Gyrfalcon {Falco rusticolus gyrfalco}. Most of the variations of other Gyrfalcons are in color only.
The Gyrfalcon is the largest falcon in the world; the male is 22 inches long, the female 24 inches. The wingspan of the Gyrfalcon is 8 1/3 to 9 1/6 feet. As with most raptors, the female is slightly larger than the male.
The upper body is brown-gray with white markings. The head is the same color, unstreaked, while the under parts are white with dark gray-brown markings. The Gyrfalcon has a "mustache" of black, a light and dark barred tail, and brown eyes. The beak is blue, the legs bluish gray and the talons black. The immature Gyrfalcon is almost identical except that the body is mainly unstreaked and the head may have light streaks on it.
The Gyrfalcon's range is found mainly in the Arctic and sub-Arctic regions of the world. Prefers rocky coasts and islands close to sea bird colonies for easy hunting, river bluffs, and mountains north of the treeline (the treeline is between forested areas and where trees can no longer grow). The Gyrfalcon prefers open spaces in which to hunt. In the winter some Gyrfalcons may migrate as far south as the northern US.
The Gyrfalcon may use a bare cliff ledge for a nest, but usually has a twig nest lined with feathers. The female lays 2 to 4 eggs. The eggs are from yellowish red to dark brown, evenly speckled with red-brown.
Feeds mostly on birds, such as Ptarmigan and sea birds. It also eats mammals such as lemmings, ground squirrels, and hares. It is said to be the only bird able to chase down another bird in level flight.
The Gyrfalcon is a favorite to falconers because of its size. It is common in some places of its range, and rare in others. In the Middle Ages, a Gyrfalcon was carried by high nobility only. Not much is known about this powerful Arctic bird.