Booby is a common name for some members of the family Sulidae, large, streamlined sea birds. Tropical and subtropical members of the family are called boobies; those of northern waters are called gannets. These birds have heavy bodies; long, pointed wings; long, wedge-shaped tails; and short, stout legs. They fish by diving on their prey from great heights and pursuing it underwater; air sacs under their skin cushion the impact with the water and provide buoyancy, as with pelicans.

The masked, red-footed booby Sula sula, and brown booby Sula leucogaster (pictured here) are found the world over; the Peruvian and blue-footed S. nebouxii boobies, on the west coasts of the Americas; and the Abbott's booby, in the Indian Ocean. The common gannet Sula bassana ranges southward from the Gulf of St. Lawrence as far as the Gulf of Mexico. A Pacific gannet is one of the chief guano producers of the offshore islands of Peru. Gannets build crude nests of debris on narrow cliff ledges. The female lays a single egg, which she and the male incubate by covering it with their feet. Gannets have strong migration tendencies, while the boobies do not. The name booby is descriptive not only of the rather stupid facial expression of these birds, but also of their unwary, gullible behavior when hunted by manÑa factor that accounts for their diminishing numbers.