Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans. Some definitions of the term 'waterfowl' include the saltwater shorebirds or waders, gulls, pelicans, and herons, as well as seabirds such as the albatross, but 'fowl' especially refers to birds used by humans for game. They have historically been an important food source, and continue to be hunted as game, or raised as poultry for meat and eggs and are sometimes kept as pets.