The consummate falcon of the Arctic region - the Gyrfalcon - is a bird that stirred the imagination of Kublai Khan and was written about by Marco Polo. It is a large and powerful falcon with plumage that varies from nearly pure white through very dark sepia and tones of streaked gray in between. The Gyrfalcon lacks the large mustache of the Peregrine Falcon, and the two-toned underwing of both the gray-morph and dark-morph birds distinguish them from other larger falcons. The two-toned underwing is less pronounced on adult gray-morph Gyrfalcons. The white birds are unlike any other. The flight is fast and powerful.
Nesting is on cliffs in the northern latitudes, with most birds spending the entire year close to the breeding grounds. Post-breeding dispersal brings some birds as far south as the northern United States every year, providing excitement and anticipation amongst birdwatchers anxious to see the "big northern Gyrfalcon!"
SIZE
The Gyrfalcon is the largest of the North American falcons. The females vary from 20.5 to 25.5 inches (52.1 to 64.8 centimeters) with an average of 22 inches (55.9 centimeters) in length, and wingspreads from 47 to 53 inches (119.4 to 134.6 centimeters). Their weights vary from 2.5 to 4.4 pounds (1134 to 1996 grams). Males are slightly shorter at 19 to 22.5 inches (48.3 to 57.2 centimeters) with an average of 21 inches (53.3 centimeters), and wingspreads from 40 to 49 inches (101.6 to 124.5 centimeters). They weigh between 1.75 and 2.9 pounds (794 to 1,315 grams). Weight ranges of live birds captured in the wild can vary depending upon breeding condition, time of year, and whether prey has been recently captured and is still in the crop. In one study, live captured migrants in Greenland did not exhibit such a wide weight variation with females averaging 3.2 pounds (1,451 grams) and males 2.8 pounds (1,270 grams).
MORPHS AND MOLTS
The Gyrfalcon ranges in color from pure white birds with darker spots, through degrees of gray to an extreme of very dark brown. This has led many authors to describe three morphs, or color phases, as white, gray, and dark or black. Others disagree with such divisions and suggest that color variation is a continuum from white to dark with much variation between. The specific descriptions follow this latter philosophy, but for ease of organization it will arbitrarily deal with white, gray, and dark groupings of plumages. Sexes are generally alike but males can be lighter overall than females, especially in gray-morph birds. Often in males, the saturation of dark pigments is not as great as in females but this is not universally true.
Molting occurs annually, and following the juvenile plumage, birds reach adult plumage after the first molt (2nd calendar year of life). Appearance does not change with subsequent molts. Molt in the adults begins while the young are still in the nest but the ability to fly is never lost. Wings and tail begin to molt first, followed by body feathers, with the entire process lasting about five months (in captive birds). Molt from the juvenile into adult feathering starts with the body feathers during the first winter. The wings and tail feathers start at the same time as the adults, which is in the April to May period.
SPECIFIC DESCRIPTION
Adult Dark-morph - Flight
- large, dark-bodied falcons with a very two-toned effect on the underwing linings
- the underwing coverts are dark with some white markings and the flight feathers are grayish
Immature Dark-morph - Flight
- a large dark falcon with two-toned underwing; dark coverts and paler flight feathers as in adults
- somewhat less white markings overall
SIMILAR SPECIES
Evolutionarily, the Gyrfalcon is felt to be related to the Saker Falcon of Eurasia. Under certain conditions in the field, this bird is most likely to be confused with the Peregrine Falcon. The "Peale's" race of the Peregrine Falcon is dark and may be confused with darker Gyrfalcons, especially in immature plumage. The uniformly dark underwing of the Peregrine Falcon versus the two-toned underwing of the Gyrfalcon are important distinctions. The Gyrfalcon and Peregrine Falcon have different wing-to-tail ratios. When perched, the wings are much shorter than the tail on the Gyrfalcon while they are equal, or nesrly so, on the Peregrine Falcon. Occasionally, the Northern Goshawk may be mistaken for the large falcon as its wingbeats and wing tips are very similar. The pale, barred underwing and heavily-banded tail of the Northern Goshawk distinguishes it. Partially albinistic Red-tailed Hawks may be confused with white-morph Gyrfalcons, but dark marks on the nape, usually some red in the tail, and lack of clear area at dark wing tips should easily separate this buteo from the falcon. In flight, wing shape and flight style will distinguish the Red-tailed Hawk immediately.
OTHER NAMES
The Gyrfalcon is also known as "Black" Gyrfalcon, "Gray" Gyrfalcon, "Gyr:, "Jerfalcon", "Partridge Hawk", and "White Gyrfalcon."
ETYMOLOGY
The genus Falco is of Latin origin and means "sickle." This is likely in reference to the shape of the talons. The species name rusticolus is also from Latin and appears to be a construct of two words - rusticus, "countryman" and incola, "inhabitant." Combined, the words therefore mean "an inhabitant of the countryside", referring to this falcon's habitat of wide open, wild spaces. Gyr is traceable to the Old High German language and the word "giri" meaning greedy. Thus, this is the greedy falcon.
MYTHOLOGY
The Gyrfalcon has long been a coveted species in the world of falconry and prized as one of the most glamorous and mystical of the birds of prey.
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