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 belly ranging from small and crisp to big and chunky. Breeds on cliffs on Arctic tundra; winters in large open areas. Never common even on breeding grounds; rare everywhere in the continental U.S. Bulkier and shorter-winged than Peregrine Falcon with more diffuse face pattern and silvery undersides on flight feathers. Feeds on birds and mammals.