Brown Booby: This large seabird is mostly dark brown with white under wing coverts, belly and vent. It has a blue-gray to yellow bill and yellow legs and feet. To acquire food, it plunge dives from 30 to 50 feet. It feeds on parrot fish, flatfish, mullets and other fish. It has alternating strong rapid wing beats and glides. The sexes are similar.
Range and Habitat
Brown Booby: May be found worldwide in tropical seas; summer visitor to the Gulf coast and Caribbean Sea; may occur casually farther north along the Atlantic coast; occasionally seen in southern California’s Salton Sea; may also occur accidentally along Pacific coast. Pelagic, breeds on coastal islands.
Boobies and Gannets (Sulidae)
Six families are included in the PELECANIFORMES (pronounced pel-leh-KAN-ih-FOR-meez), the order that includes the long-necked darters, the beautiful tropicbirds, and the gannets and boobies.
The boobies and gannets compose the Sulidae (pronounced SOO-li-dee) family; a group with ten species in three genera occurring in most of the world’s seas.
Seven species of Sulidae (commonly called “Sulids”) in two genera have occurred in North American waters. These seven species include the Northern Gannet and the booby species such as the Masked and Brown Booby of warmer waters.
The Blue-footed Booby is known for its comical courtship displays that involve showing off its blue feet by raising one and then the other into the air. All members of this family are also known for the spectacular dives they make into the water when foraging.
The Sulidae are large birds with long, pointed wings, a long tail, and a fairly long, thick neck. They have longish, sharp, conical bills and short legs with large webbed feet.
Adult gannets are mostly white with black in the wings, their young with mostly brown plumage. Young of booby species also have brown plumage with varying amounts of white. The adults of the other booby species are white with brown, gray, and black markings or are overall brown (the Red-footed Booby showing both brown and white phases). Other colors are limited to bills and feet, and include blue, pink, red, and yellow.
In North America, Sulids occur in coastal and offshore waters although birds occasionally show up as vagrants on large inland bodies of water such as the Great Lakes and the Salton Sea. On land, these aquatic birds are only encountered at their cliff or island breeding colonies. The only species that breeds in such colonies in the northern United States and Canada is the Northern Gannet of the Atlantic Ocean. This common Sulid winters in coastal waters further south where it occasionally shares the water with individuals of tropical Sulid species. The only Sulids that occur on the Pacific Coast of the United States are vagrants from Mexico.
The Northern Gannet migrates from its North Atlantic breeding grounds south to Florida, the other species non-migratory.
Sulids are fairly social birds that nest in large colonies, and migrate and forage together in flocks. Their mode of foraging is spectacular; from forty or more feet above the waves, they fold their wings back and dive into the water headfirst to snatch unwary fish.
Although North American Sulid species are not threatened, potential threats exist in the form of oil spills, pollution, and global warming. Introduced rats can also threaten breeding colonies of these birds; a scenario that wiped out the Brown Booby on Midway Atoll.
Unlike birds with brood patches for incubating their eggs, booby species incubate their eggs with their feet. Although Sulid species often lay two eggs, when the second hatches, the first kills its sibling by ejecting it from the nest.