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The Canadian Peregrine Foundation -- Raptor Identification Gallery

The Canadian Peregrine Foundation

Raptor Identification - Gyrfalcon

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Gyrfalcon (Falco rusticolus)
The Gyrfalcon is North America’s largest falcon (similar in size to a Red-tailed Hawk or Raven) and breeds exclusively in the Arctic. Even in the winter it rarely ventures south of Canada. In addition to the size difference, Gyrfalcons can be told apart from Peregrines by their lighter underwings and narrow or absent moustaches.

 

The following article about Gyrfalcons was reproduced (with modifications) from the March 2002 issue of CPF's Talon Tales. The article was written by Marcel Gahbauer.

Etymology:
The gyrfalcon’s name is thought to be derived from the Latin hierofalco, meaning "sacred falcon" in reference to the bird’s exalted position in falconry, where it was traditionally reserved for use by only kings and princes. Alternatively, it may come from the old German gir, meaning "greedy", recognizing the bird’s voracious appetite. The scientific name is Falco rusticolus, which is Latin for "falcon living in the country", acknowledging its tundra habitat. The species has also been known as jer-falcon, gerfalcon, Greenland falcon, and Iceland falcon.


An adult white-phase gyrfalcon at Mont St-Hilaire, Quebec
Photo by Pierre Molina


Description and identification tips:
The largest of the world’s falcons, the gyrfalcon has a heavier body, broader wings, and longer tail than the peregrine. Males range in size from 50-54 cm, with a wingspan of 110-120 cm, and a weight of 1.0-1.3 kg. Females are much heavier, ranging from 1.4-2.1 kg, and are visibly larger with a length of 57-61 cm and a wingspan of 124-130 cm.

The gyrfalcon is unusual among birds in having three distinct colour morphs, generally referred to as white, gray, and dark (or black). White morph birds often lack a malar stripe on the face, are only faintly marked with black flecks below, and moderately barred with black above. The gray form is a fairly uniform slate-gray above, and whitish below with dark barring, and usually has a distinct malar stripe. Dark individuals typically have a uniformly gray-brown head and back, and heavy dark streaking below. Considering the variation which exists, some believe that the dark and gray forms are simply extremes of a gradient. As a general rule, colour varies from dark gray in Alaska to light gray in the eastern Arctic and white in Greenland. In all colour morphs, juveniles are noticeably browner and have an overall darker appearance. Furthermore, adults can be told apart from juveniles by the colour of the skin on the feet, eye-ring, and cere: yellow to orange on adults, and bluish-gray on juveniles, as is the case with peregrines.

Habitat and distribution:
Like its smaller relatives the peregrine and the merlin, the gyrfalcon has a circumpolar distribution, but in contrast to them is restricted to the far north. Preferred nesting habitat includes rocky coastlines, especially near seabird colonies, as well as inland cliffs. Remarkably, some gyrfalcons remain near their breeding grounds throughout the year, but others may travel as far south as the northern United States in some winters. Those individuals which do migrate often settle in coastal areas where waterfowl are plentiful, and typically select a habitual roost which they return to nightly.

Natural history:
Gyrfalcons usually nest in late April or May, prior to which they engage in intricate aerial courtship displays often involving steep dives. Individuals usually begin breeding at two or three years of age, and pair bonds are formed for life. Nest sites tend to be similar to those favoured by peregrines, namely cliff ledges, preferably with some degree of shelter. However, gyrfalcons may also take over the old stick nests of ravens or golden eagles. Nests are used year after year, though in some cases a pair may cycle among several alternate sites.

As many as eight eggs have been recorded in a nest, but the usual number is three to four. The yellowish-white eggs have reddish-brown markings, and average 59 mm in length. Females do nearly all of the brooding, and in exchange the males provide all food during the five-week incubation period. The young are able to feed themselves by the time they are one month old, and usually fledge just under three weeks later. They remain dependent on their parents for approximately another month after that.

In most areas, the gyrfalcon’s diet is primarily birds, especially ptarmigan and colonial seabirds; in fact, in some areas fluctuations in the gyrfalcon population are thought to be related to ptarmigan numbers. Some gyrfalcons also hunt mammals quite extensively, focusing on lemmings, hares, and ground squirrels. Two main hunting approaches are used. The passive method is to perch on an outcrop, watch for prey, then dive toward it. More commonly, they use an active "contour-hugging" approach, in which they fly low over the ground, surprising prey at close range, then pursuing it over sometimes long distances. Typically the gyrfalcon flies with slow, deep, powerful wingbeats which give it a rapid level flight; on occasion it may hover briefly while searching for prey.

Conservation status:
Because it is seen so rarely in southern Canada and the northern United States, any gyrfalcons which do make winter visits to the south attract large crowds of observers eager to catch a glimpse of these majestic birds. However, as a species they are thought to be relatively common, though accurate population estimates are limited by the remoteness of the breeding range. Population declines have been reported over parts of the Eurasian range, and are attributed to a combination of shooting, egg collection, and removal of adults for international trade. Unlike peregrines, gyrfalcons suffered little from DDT, since they rarely ventured south into areas where pesticides were used, and also hunt primarily sedentary prey.

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