Ascension Island Government

Conservation > Discover > Flora and Fauna > Brown Booby

Brown Booby

Sula leucogaster

Type: Seabird | Status: Least Concern | Nativeness: Native


On Ascension Island, brown boobies can be found nesting scattered throughout Letterbox Nature Reserve. They also can be seen nesting on the cliffs of Boatswain Bird Island and on rocky stacks along the coast, such as White Rock. Interestingly, many brown boobies choose to nest within Ascension frigatebird colonies, despite the threat of predation that frigatebirds pose to young chicks. Nests are usually a small depression in the ground and there is often a variable amount of nesting material loosely gathered around it. This material is often gathered feathers and possibly sticks or some dry grass if it is available. However, despite Ascension's remote location they have also been recorded using marine plastic in their nests, commonly green rope and netlon tubes. This is a topic of study for the Conservation directorate. Two eggs are usually laid, though only one chick will be reared to fledging.

Brown boobies are typically inshore feeders that nest on the ground and prefer to perch on rocks rather than settle on water. Gregarious in nature, brown boobies typically occur in small groups, aggregating on cliffs and stacks. They can be seen in larger flocks when food sources are prevalent. Groups usually fly close to the water and execute low level raking plunge-dives.

The upper parts of the adult bird are a chocolate brown colour whilst the underside is a plain white. The bill, facial skin and legs of the adults are a contrasting yellow colour. Sexes are similar in resemblance, with wingspans reaching between 132-150cm. They are the smallest of Ascension's three booby species. Juveniles are a lighter brown all over, with a lighter mottled underside, while the bill and facial skin is grey.