The family Sulidae includes 5 species found in North America.

Boobies and Gannets occur on the coasts and islands of the oceans of the world. Boobies are tropical and subtropical; gannets occur in temperate regions. They spend long periods at sea, often far from the breeding areas. The sulids are medium to large-sized birds (940-3100 gms) with long, relatively narrow wings and a long, wedge-shaped tail. Sexes are the same size in gannets. Females are larger than males in boobies. The bill is straight, strong, pointed, with a curved nail at the tip.

Food is mainly fish and squid, including many different species. Food is taken mainly by plunge-diving from various heights (up to 45 meters). They also dive from the surface and pursue prey under water, or on foot in shallow water. Some boobies capture flying fish and squid on the wing. Some species hunt in groups and some scavenge.

All sulids except Abbott's Booby nest in colonies. Nests are on the ground, cliff ledges or in trees. Ground scrapes or shallow depressions are unlined, or loosely woven nests of twigs and debris. Nest construction is by both sexes, but the male usually brings the material. Eggs are pale blue, green or white with chalky coat and becoming stained with brown. Clutch 1 in gannets, 1-4 in boobies, laid at intervals up to 5 days. Incubation begins with the first egg. Incubation is 40-57 days by both sexes with eggs cupped between the foot webs. Hatching is asynchronous and a full clutch of more than 1 egg is seldom reared unless the food supply is ample and close to the nest. Sibling murder occurs in broods of two or more. Young are fed and cared for by both parents. Young are usually fed by incomplete regurgitation in which the young take the food from the gullet of the adult. Fledging is at 86 to 170 days, varying with the food supply. Gannets become independent at fledging; boobies with variable periods of post-fledging care at the nest site or as free-flying juveniles. Age at first breeding is 2-6 years. Adults of most species do not breed every year.