- Sula leucogaster
- Dark brown head, neck, tail and upper body
- White lower breast and abdomen
- Light colored bill
- Ivory colored in the Caribbean, but in other populations can be pinkish or even light bluish
Male has blue facial skin
It takes about three years for this species to reach full adult plumage.
- Nominate race shows paler lower back and tail
- plotus from Red Sea has uniformly dark upperparts
- brewsteri can show pale head and throat, most extreme at Clipperton where the brown in front is reduced to a narrow breast band.
- Uniform brown
- Slightly lighter belly
- Contrast between darker belly and white in underwing coverts
 Similar Species
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 Red-footed Booby.
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.
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.
There are 4 subspecies:
- 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 Colombia.
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.
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, B.L. Sullivan, C. L. Wood, and D. Roberson. 2012. The eBird/Clements Checklist of Birds of the World. 6th ed., with updates to October 2012. Ithaca: Cornell Univ. Press. ISBN 978-0801445019. Spreadsheet available at http://www.birds.cornell.edu/clementschecklist/downloadable-clements-checklist
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