The Gyrfalcon (pronounced /ˈdʒɜrfɔːlkən/ or /ˈdʒɜrfælkən/; also spelled gerfalcon) Falco rusticolus is the largest of the falcon species. The Gyrfalcon breeds on Arctic coasts and the islands of North America, Europe, and Asia. It is mainly resident there also, but some Gyrfalcons disperse more widely after the breeding season, or in winter.[nb 1] The Gyrfalcon is dispersed throughout much of the Northern Hemisphere, with populations in Northern America, Greenland, and Northern Europe. Its plumage varies with location, with birds being coloured from all-white to dark brown.
The bird’s common name comes from French gerfaucon; in medieval Latin it is gyrofalco. The first part of the word may come from Old High German gîr (cf. modern German Geier) for “vulture”, referring to its size compared to other falcons; or from the Latin gȳrus for “circle” or “curved path”—from the species’ circling as it searches for prey, distinct from the hunting of other falcons in its range.[nb 2] The male Gyrfalcon is called a gyrkin in falconry. The scientific name is composed of the Latin term for a falcon, Falco, and for a countryside-dweller, rusticolus.