The males have colored inflatable throat pouches. They do not swim or walk and cannot take off from a flat surface. Having the largest wingspan-to-body-weight ratio of any bird, they are essentially aerial, able to stay aloft for more than a week. Order: SuliformesFamily: Sulidae  The sulids comprise the gannets and boobies. Both groups are medium-large coastal seabirds that plunge-dive for fish. Order: SuliformesFamily: Phalacrocoracidae  Cormorants are medium-to-large aquatic birds, usually with mainly dark plumage and areas of colored skin on the face. The bill is long, thin, and sharply hooked. Their feet are four-toed and webbed. Order: SuliformesFamily: Anhingidae  Anhingas, also known as darters or snakebirds, are cormorant-like water birds with long necks and long, straight beaks. They are fish eaters, diving for long periods, and often swim with only their neck above the water, looking rather like a water snake. Order: PelecaniformesFamily: Pelecanidae  Pelicans are very large water birds with a distinctive pouch under their beak. Like other birds in the order Pelecaniformes, they have four webbed toes. Order: PelecaniformesFamily: Ardeidae  The family Ardeidae contains the herons, egrets, and bitterns. Herons and egrets are wading birds with long necks and legs. Herons are large and egrets are smaller. The cattle egret or "cow bird" is seen amongst flocks of cattle, for instance in ranches north of the Everglades. A bird will often attach itself to a particular bull, cow or calf, even being tolerated perching on the back or even the head of the animal. The birds are more shy than the animals, and will fly away if approached. The birds feed on various items turned over by the cattle as they graze and tramp the ground. Bitterns tend to be shorter necked and more secretive. Unlike other long-necked birds such as storks, ibises, and spoonbills, members of the Ardeidae fly with their necks pulled back into a curve. Order: PelecaniformesFamily: Threskiornithidae  The family Threskiornithidae includes the ibises and spoonbills.