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 wit::-flightph
h 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 White-morph - Perched
HEAD
- virtually entirely white in the lightest birds
- variable amounts of dark brown/black streaking on the crown extending into spots on the nape.
- throat white
- beak variously described as yellowish -brown to yellowish-gray basally and dusky at the tip
- the cere is light yellow and the eyelids flesh to pale flesh
- the eye is dark brown
BODY
- the entire body is white with the breast and abdomen immaculate, except for a few dark spots
- the flanks have dark spotting as well
- the back is usually barred with dark, sepia markings that vary in extent and intensity
WINGS
- the wings are basically white with dark tips and varying degrees of barring as for the back
- the wing tips reach one-half or two-thirds of the way down the tail in perched birds
TAIL
- the upper surface of the tail may be cleanly white or variably streaked or barred, but more narrowly in the rump area
- the undertail coverts are usually unstreaked white
LEGS
- the legs and feet are yellow and talons black
Immature White-morph - Perched
Note that immatures are overall very similar to the adults but are browner dorsally
HEAD
- finely streaked with dark brown
- the beak bluish horn with darker tip
- cere and eyelids are bluish
- the eye is very dark
BODY
- underparts white with short, dark brown streaking
- back is mostly dark brown but feathers can have broad white edgings
- whiter individuals can lack streaking on the underparts and the dark areas on the dorsal feathering can be much reduced
WINGS
- as for adults
TAIL
- as for adults
LEGS
- the legs and feet are bluish and the talons dark brown to black
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.
VOICE
The voice is generally louder, gruffer and deeper than that of the Peregrine Falcon, but many features are similar. The male's voice is higher pitched than that of the female. A gutteral "kak-kak-kak" is given by both sexes as a territorial threat and mobbing call. The male will also give this during some flight displays with his mate. The wailing call is a two syllable vocalization that is used in a variety of courtship and other heterosexual situations. It is given mainly by males but females will utter it during copulation and after receiving food. A number of variations are used. A single syllable "chup" call is given by both sexes during various courtship displays and at other times during the nesting period. A faster version of this call known as the "chattering" call is also given during ledge displays and food - passing ceremonies. A "chittering" call is given by both sexes and is featured during copulation activities. Other calls include loud trilling, screams and rattling as well as variants of some of the above calls. Food begging calls of the young are querulous mewings and juveniles have been heard giving deep raven-like calls.
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