Brown Booby

The Brown Booby (Sula leucogaster) is a large, conspicuous seabird belonging to the family Sulidae. It is the most common and widespread member of its family, with a pantropical distribution. The adult male is slightly smaller than the female, with a length of about 75 centimeters and a wingspan of up to 140 centimeters, weighing up to 1,000 grams. The female is larger, reaching about 80 centimeters in length, with a wingspan of up to 150 centimeters and a weight of up to 1,300 grams. The species exhibits sexual dimorphism in bare part colors, with males sporting a blue orbital ring and females a yellow one. The plumage is dark brown to blackish on the head and upper body, with a contrasting white belly.

Identification Tips

To identify the Brown Booby, look for its sharp beak with jagged edges, short wings that result in a fast flap rate, and long, tapered tail. The male of the subspecies S. l. brewsteri is distinct with a white forehead, forecrown, and chin, merging into a greyish-brown neck and breast. Juveniles resemble adults but are gray-brown with darkened upper surfaces and heavily flecked brown on white lower breast and underparts.

Habitat

Brown Boobies breed on islands and coasts in tropical areas of the Atlantic and Pacific oceans. They are often found in large colonies on the breeding grounds of islands in the Gulf of Mexico and the Caribbean Sea.

Distribution

This species has a pantropical range, with four recognized subspecies distributed across the Caribbean and Atlantic Islands, Pacific coasts of the USA and Mexico, Pacific coasts of Central America and Colombia, and from the Red Sea through the Indian Ocean to the west and central Pacific.

Behaviour

Brown Boobies are gregarious birds that commute and forage at low heights over inshore waters. They are known for their elaborate greeting rituals and are spectacular divers, plunging from high speeds into the ocean. They are powerful and agile fliers but are clumsy during takeoffs and landings, often using strong winds and high perches to assist their takeoffs.

Song & Calls

Typically silent, the Brown Booby occasionally emits sounds akin to grunting or quacking.

Breeding

The Brown Booby nests on the ground in large colonies, laying two chalky blue eggs in a mound of broken shells and vegetation. Generally, only one chick is raised to adulthood, as the second chick is unable to compete for food or is ejected from the nest by its older sibling.

Similar Species

The Brown Booby can be distinguished from other species of sulid by its size, plumage, and the color of the orbital ring, which varies between males and females.

Diet and Feeding

The diet consists mainly of small fish, squid, and shrimp. Brown Boobies catch their prey by plunge-diving into groups of fish near the surface or by skimming the surface to catch leaping fish. Some individuals also engage in kleptoparasitism, stealing prey from other seabirds.

Conservation status

The Brown Booby is currently listed as Least Concern on the IUCN Red List of Threatened Species. However, with the rise in pollution, these birds have been observed using marine debris, including plastic, to construct their nests.