Falco rusticolus

Morphology 4

The world's largest falcon is polymorphic, being recognized in three color phases: white, grey, and dark. The dark phase is dark grey, almost black, in some individuals and groups of this morph are found in northern Canada. The white morph is generally found in Greenland, and is usually almost pure white with some markings usually on the wings. The grey morph is an intermediate and found throughout the range, typically two tones of grey are found on the body, most easily beind seen on the flight feathers versus the rest of the wing. This species is sexually dimorphic and thus has a wide ranging weight. Males weigh 800-1300g, averaging 53cm total length and females weigh 1400-2100g, averaging 56cm total length. The shape of the gyrfalcon is characteristically the same as most falcons. This includes long pointed wings (unlike the rounded wings of buteos), long tail and a notched bill. It also however, differs from other falcons by large size, shorter wings that only extend 2/3 down the tail when perched (compared with other falcons where the wings extend all the way to the tail), and broader wings. Adults characteristically have yellow ceres, eye-rings and legs while juveniles display these features in a blue color. As in all falcons, the eyes appear black. This species may perhaps only be confused with the Northern Goshawk (Accipiter gentilis) which inhabits dense forests, or the Peregrine Falcon (Falco peregrinus) which is somewhat smaller with a dark slaty-blue-black "helmet" and a lighter underside(Wheeler and Clark 1995; Cade 1982).

Trophic strategy 5

Unlike eagles which use their large size to rob meals, and peregrine falcons which use gravity to gain tremendous speed, the gyrfalcon uses raw power to capture prey, usually in a tail chase. Usually low coursing flights are used in open habitat (no trees for concealment) where gyrfalcons will strike prey both in the air or on the ground . The majority of prey (by biomass) that consitutes the diet consists of ptarmigan (Lagopus sp.), Arctic ground squirrel (Spermophilus parryii) and Arctic hares (Lepus arcticus). Other prey includes other small mammals (mice and voles) as well as other birds (ducks, sparrows, buntings)

While hunting, this falcon uses keen eyesight to spot potential prey, as almost all animals in the north are cryptically colored to avoid detection. When potential prey is spotted a chase usually occurs where more than likely the prey will be knocked to the ground in a powerful blow from the talons and then pounced upon. Gyrfalcons are powerful enough to have sustained flight while hunting and occasionally wear their prey out until capture is easy. During nesting, the gyrfalcon will also cache meals with large prey such as Arctic hares between feedings. Rock doves (Columba livia), or pigeons as they are commonly known, although not native are preyed upon heavily in major centers by gyrfalcons during winter months (Lange and Dekker 1999; Stelfox and Fisher 1998; Cade 1982; Poole 1987).

Sources and Credits

  1. (c) Bill Gracey, some rights reserved (CC BY-NC-ND),
  2. (c) *Falco_rusticolus_white.jpg: Ólafur Larsen *derivative work: Bogbumper (<span class="signature-talk">talk</span>), some rights reserved (CC BY-SA),
  3. (c) Ómar Runólfsson, some rights reserved (CC BY),
  4. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA),
  5. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA),

More Info

Range Map Map

Animal Bird
Bird Birds of Prey (Accipitriformes)
Color brown, grey, white