Gyrfalcon, Falco rusticolus

Kingdom:  Animalia

Phylum:  Chordata

Class:  Aves

Order:  Falconiformes

Family:  Falconidae

Genus:  Falco

Species:  rusticolus

Status

Considered “Least Concern” by the International Union for the Conservation of Nature.  The U. S. Fish and Wildlife Service does not reference this species.

Description

Females are larger than males.  Range in color morphs from pure white to dark gray with dark bars on the underside of the wings and tail.  Most are a lighter gray with light mottling on the chest and belly and barring on the underside of the wings and tail.  Females weigh up to 1500 grams with males weighing in around 900 grams.

Habitat and Range

Inhabit the Arctic tundra, northern coniferous forests, and arctic-alpine regions of North America, Greenland, Iceland and Eurasia.  Generally not migratory, some populations begin ranging farther south if their main prey (ptarmigan) populations decline.  The Gyrfalcon’s ability to switch to other prey allows it to survive year-round in the same territory.

Diet

Feed mainly on ptarmigan and grouse.  However, Gyrfalcons may take other birds and even mammals such as lemmings, arctic hare, and ground squirrels according to seasonal availability.

Reproduction

Nest in crevices and on shelves on the sides of tall cliffs.  Gyrfalcons incubate broods of 3-7 eggs annually (average 4 eggs per brood).  After 34-36 days, young hatch and then fledge 45-50 days later.  Fledglings remain dependent upon parents for a further 3-4 weeks.

Behavior

Gyrfalcons will stoop, swoop, hunt cooperatively, or fly fast and close to the ground.  In so doing, the Gyrfalcon will suddenly come upon prey, flush it out, and pursue.  In this pursuit, the Gyrfalcon reaches speeds significantly faster than the Peregrine in level flight.  Estimates of exact speed range greatly, though a conservative average is 90 miles per hour in level flight and 150 miles per hour in stoop.  A study of captive birds on a lure course found peregrine falcons flew up to 30 miles per hour and gyrfalcons reached 40 miles per hour in level flight.  These were captive birds in a situation with a known reward, meaning hungry, wild individuals would likely move faster.

Wow!

  • The largest and most powerful of the falcons.
  • In medieval times, this species would often be owned by kings as a sign of power.