Brown Booby

Overview

The Brown Booby is the most widely distributed booby species, found across tropical and subtropical oceans worldwide. It shows a distinctive two-tone plumage pattern, with dark chocolate-brown covering the head, chest, and upperparts sharply cut off from clean white on the lower belly and underwing.

This crisp demarcation line across the breast is one of the most useful identification features among the booby species, making Brown Booby relatively easy to distinguish from its close relatives.

Brown Booby feathers show one of the sharpest color divisions among the booby species.

• Upperparts and chest: Uniform dark chocolate-brown, extending down over the head, neck, back, wings, and upper breast without mottling.
• Underparts: Bright white lower belly and underwing coverts, with a crisp, clean line separating the brown chest from the white belly.
• Flight feathers: Dark brown, consistent with the rest of the upperparts.
• Compared to Blue-footed and Masked Booby: The sharp brown-to-white demarcation line across the breast is more clean-edged than the gradual streaking of Blue-footed Booby, and unlike Masked Booby, Brown Booby's dark coloring covers the head and chest rather than being restricted to a facial mask and flight feathers.

Adults show a uniform dark chocolate-brown head, neck, chest, back, and upperwing, sharply demarcated from white lower underparts and underwing coverts. Sexes look similar, with some subtle differences in facial skin color. Juveniles are more uniformly brownish overall, lacking the crisp adult demarcation line, and gradually develop the sharp two-tone pattern with maturity.

Brown Boobies breed on tropical and subtropical islands across the Atlantic, Pacific, and Indian Oceans, nesting on the ground on rocky or sandy islets. They forage over nearshore and offshore waters and are generally less pelagic than some other seabirds, often remaining within sight of their breeding islands or nearby coastlines throughout the year.

This booby feeds by plunge-diving from low to moderate heights, often foraging alone or in small groups close to shore, and readily catches flying fish in the air as well as diving for schooling prey. Nesting occurs on bare ground or low vegetation, with typically two eggs laid, though usually only one chick survives to fledging. Calls include harsh honking and quacking notes given at breeding colonies, differing somewhat between the sexes.