Stocky beast of a falcon; ranges in color from strikingly white to silvery-gray to dark sooty-brown. Relatively long tail and broad wings with powerful flight. Generally darker above and paler below, with markings on the belly ranging from small and crisp to big and chunky. Breeds on cliffs on Arctic tundra; winters in large open areas. Scarce even on breeding grounds. Bulkier and shorter-winged than Peregrine Falcon with a more diffuse face pattern and silvery undersides on flight feathers. Feeds on birds and mammals.