Pelicans are a genus of large water birds that makes up the family Pelecanidae. They are characterised by a long beak and a large throat pouch used for catching prey and draining water from the scooped up contents before swallowing. Long thought to be related to frigatebirds, cormorants, tropicbirds, gannets and boobies, pelicans instead are now known to be most closely related to the shoebill and hamerkop, and are placed in the order Pelecaniformes. Ibises, spoonbills, herons and the desolate bitterns have been classified in the same order. Pelicans frequent inland and coastal waters where they feed principally on fish, catching them at or near the water surface.