- Sula leucogaster
Description
Adult: is quite distinctive with dark brown head, neck, throat, upper breast, mantle, wings, and tail contrasting with white lower breast and abdomen. Bill is light colored, ivory colored in the Caribbean, but in other populations can be pinkish or even light bluish. Blue facial skin indicates a male.
Variation: Nominate race shows paler lower back and tail, race plotus from Red Sea has uniformly dark upperparts. Race brewsteri can show pale head and throat, most extreme at Clipperton where the brown in front is reduced to a narrow breast band.
Juvenile: quite uniform brown, not quite as dark as the brown in the adult. The belly will often be slightly lighter, hinting at the pattern of the adult, and there should always be a contrast between darker belly and some white in the underwing coverts.
Identification
The juvenile can be somewhat difficult to separate from the juvenile Red-footed Booby, but the latter lacks white in the underwing, it shows darker primaries and most secondaries where the upperside of the wing is rather uniform in Brown Booby, and in addition, head and neck is lighter than the mantle in the RFB.
Distribution and Taxonomy
Found in tropical seas breeding on numerous islands throughout Atlantic, Indian and Pacific Oceans. Most stay fairly local to their natal islands but some disperse for much greater distances.
In the Western Palearctic recorded regularly around the Cape Verde Islands where race leucogaster breeds on Santiago, Brava, Rombo, Razo and islets off Boa Vista; this form also breeds in islands of the Gulf of Mexico and the Caribbean. In the Red Sea race plotus occurs in the Gulf of Aqaba and breeds on the islets of Gezira Ashrafi, Gezira Qeisum, Gezira Umm el Heimat and Gezira Umm Qamar in the mouth of the Gulf of Suez; this subspecies also breeds in the Indian Ocean and south China Sea. Outside the western Palearctic are found the subspecies brewsteri on islands in the gulf of California and along western Mexico, and etesiaca which breeds on islands of Central America and Columbia.
Recorded as a vagrant off the Azores, Morocco, Mauritania and Portugal, on the Atlantic coast of Spain as casualties of the Prestige oil spill, and in the Mediterranean off southern Spain and Italy.
Habitat
Less oceanic than other boobies, although it does feed over deep water it is more commonly seen over shallow inshore waters. Breeds colonially on the ground or in rocky crevices on undisturbed islands. Fairly sedentary in vicinity of colonies.
