The Gyrfalcon is the official bird of the Northwest Territories, and it is the world’s largest falcon. It is about 50 cm long (20 in.) and its wingspan is about 1.2 m across (4 ft.). It has very stout legs and feet.
There are two main colour-variants of Gyrfalcons: they are either dark or light. The darker variety is dark grey overall with a few white streaks. The lighter variety is white overall, with black barring on the back and wings. Although the two colour patterns are quite distinct, it is not uncommon to find intermediate birds. The two varieties can be found in the same areas, although the darkest ones are found in northern Labrador and the lightest ones are more common in the High Arctic.
Gyrfalcons are known to form monogamous pairs. Scientists think that these pairings often last until one of the birds dies. Gyrfalcons generally begin to breed when they are about three years old. Toward the end of April and beginning of May, the female lays three to four buff-coloured eggs with heavy reddish brown markings. She lays the eggs one at a time, in two- to three-day intervals.
Gyrfalcons nest on cliffs or similar sites, usually under an overhang that helps protect the nest from the weather. Nest sites will be used year after year. From this repeated use, the ground around the nest is blanketed by white guano and it accumulates piles of uneaten prey-parts.
The Gyrfalcon's diet is made up primarily of birds, especially ptarmigans. While hunting, the bird relies on keen vision to spot prey. Upon sighting prey, the Gyrfalcon will initiate a chase that usually ends with the prey being knocked to the ground by a strong blow from the Gyrfalcon’s talons. The Gyrfalcon is powerful enough to have sustained flight while hunting, and it occasionally tires out the prey until the capture is easy.
Gyrfalcons are found in the Arctic regions of Europe, Asia, North America, Greenland and Iceland. Some Gyrfalcons migrate southward in the depths of winter, but they seldom go further south than the northern United States or central Russia.