From Wikipedia: The Gyrfalcon (Falco rusticolus), also spelled Gyr Falcon, sometimes Gerfalcon, is the largest of all falcon species. The Gyrfalcon breeds on Arctic coasts and islands of North America, Europe and Asia. The "g" is pronounced like the "j" in "jar".
The Gyrfalcon is a bird of tundra and mountains, with cliffs or a few patches of trees. It feeds only on birds and mammals. Like other hierofalcons, it usually hunts in a horizontal pursuit, rather than the Peregrine's speedy stoop from a height. Most prey is killed on the ground, whether they are captured there or, if the victim is a flying bird, forced to the ground. The diet is to some extent opportunistic, but a majority of breeding birds mostly rely on Lagopus grouse. Avian prey can range in size from redpolls to geese and can include gulls, corvids, smaller passerines, waders and other raptors (up to the size of Buteos). Mammalian prey can range in size from shrews to marmots (sometimes 3 times heavier than the assaulting falcon), and often includes include lemmings, voles, ground squirrels and hares. They only rarely eat carrion. The Gyrfalcon is Iceland's staðfugl (national bird), as well as the official bird of Canada's Northwest Territories. In medieval times, the Gyrfalcon was considered the king's bird. Due to its rarity and the difficulties involved in obtaining it, in falconry the gyrfalcon was generally reserved for kings and nobles.