Pelecaniformes comprises of the relatively large and diverse group of aquatic birds that share the common characteristic of webbing between all four toes. The order Pelecaniformes contains six families: Phaethontidae (tropicbirds), Sulidae (boobies and gannets), Phalacrocoracidae (cormorants and shags), Anhinidae (anhingas), Pelecanidae (pelicans), and Fregatidae (frigatebirds). Pelecaniformes are found worldwide and primarily in marine and inland waters: their habitat varies from pelagic to coastal to inland freshwater environments. They are generally medium to large birds, ranging from about 40cm to 1.8 metres in height, with feet joined by web. They primarily feed on fish and squid.