The Cocos booby, formerly known as Brewster's booby, is a species of booby in the family Sulidae. It was formerly considered a subspecies of Brown booby, but it was split by the American Ornithological Society in 2024 due to morphological and behavioural differences. It is native to the east and central Pacific Ocean.
Region
Eastern and Central Pacific Ocean
Typical Environment
Breeds on remote tropical islands and offshore islets of the eastern and central Pacific, including Cocos Island and nearby archipelagos. It forages over warm pelagic waters and along island shelf edges, drop-offs, and current convergences where prey is concentrated. Nest sites are typically open ground, low cliffs, or rocky terraces with minimal vegetation. At sea it ranges widely from colonies but generally remains within regional waters.
Altitude Range
Sea level to 200 m
Climate Zone
Tropical
Ease of Keeping
Beginner friendly: 1/5
The Cocos booby, formerly known as Brewster's booby, was split from the Brown Booby complex due to distinct morphology and behavior. It is a powerful plunge-diver that targets schooling fish and squid in warm Pacific waters. Colonies nest on remote islands and islets, often on open ground or sparsely vegetated slopes close to the sea.
S. b. brewsteri with chick
Temperament
social and active
Flight Pattern
strong flier with direct, rapid wingbeats low over the waves; occasional short glides
Social Behavior
Nests colonially on the ground, forming dense but loosely structured groups. Courtship includes sky-pointing, bill displays, and offering nest material. Both parents incubate and feed the chick, typically raising one young per season.
Migratory Pattern
Resident
Song Description
Generally quiet at sea, but vocal in colonies with harsh grunts, croaks, and whistles. Males tend to give higher-pitched whistles, while females produce deeper grunts during pair interactions.
Plumage
Dark brown upperparts and chest with a crisp boundary to a white lower belly and vent; many adults show a paler, clay-brown head and neck. Feathers are sleek and waterproof, suited to repeated plunge-diving.
Diet
Feeds mainly on small pelagic fish such as flying fish, sardines, and anchovies, as well as squid. Captures prey by high-speed plunge-dives from a few to tens of meters above the surface, often pursuing underwater using wings. Frequently forages near predatory fish or marine mammals that drive prey to the surface, and may join mixed-species feeding flocks.
Preferred Environment
Most often forages over warm, productive waters near island slopes, current lines, and upwelling zones. Regularly hunts within sight of colonies but can range offshore to locate prey patches.
