Birds and mammals commonly hunted for sport. The major groups include upland game birds (quail, pheasant, and partridge), waterfowl (ducks and geese), and big game (deer, antelope, and bears). Game animals are protected to varying degrees throughout most of the world, and hunting levels are regulated through the licensing of hunters as well as by seasons and bag limits. In the United States, state wildlife agencies assume primary responsibility for enforcing hunting regulations, particularly for resident or non-migratory species. The Fish and Wildlife Service shares responsibility with state agencies for regulating harvests of migratory game animals, principally waterfowl.