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- Sula leucogaster
Identification
64–74 cm (25¼-29 in)
Adult
- 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.
Variation
- 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.
Juvenile
- Uniform brown
- Lighter than adult
- Slightly lighter belly
- Contrast between darker belly and white in underwing coverts
Similar Species
Male Cocos Booby has head more whitish, bill more grayish-blue, and gular pouch more greenish-blue, when compared to Brown Booby. Female Cocos Booby has a whitish forehead where Brown Booby is brown. Underwing of both sexes also differ, with lesser wing coverts showing a brown bar in Cocos B. which is absent in Brown B.
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.
Immature Masked Booby can be similar to Brown Booby, but notice that the first has a white collar across the back just in front of the wings which Brown Booby does not show, and that bill color is dark in Brown where it is yellowish in Masked booby.
Distribution
Found in tropical seas breeding on numerous islands throughout Atlantic, Indian and on to the Central 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 north at least to Denmark, and in the Mediterranean off southern Spain and Italy.
Taxonomy
Cocos Booby was formerly included in Brown Booby. The split of the two was at least in part based on the observation of assortative mating where they coexist in the same colonies.
It has been proposed to divide the remaining Brown Booby into Atlantic Brown Booby (S. leucogaster) and Indo-Pacific Brown Booby (S. plotus)[5].
Subspecies
Clements recognizes these subspecies[1]:
- S. l. leucogaster: islands in Gulf of Mexico, Caribbean, and tropical Atlantic including the Cape Verde Islands
- S. l. plotus: breeds on islands in the Red Sea, tropical Indian Ocean, and tropical western and central Pacific Ocean
Habitat
Less oceanic than other boobies: although it does feed over deep water, it is more commonly seen over shallow inshore waters.
Behaviour
Breeding
Breeds colonially on the ground or in rocky crevices on undisturbed islands. Fairly sedentary in vicinity of colonies.
References
- Clements, J. F., P. C. Rasmussen, T. S. Schulenberg, M. J. Iliff, T. A. Fredericks, J. A. Gerbracht, D. Lepage, A. Spencer, S. M. Billerman, B. L. Sullivan, M. Smith, and C. L. Wood. 2024. The eBird/Clements checklist of Birds of the World: v2024. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/
- Gill, F, D Donsker, and P Rasmussen (Eds). 2024. IOC World Bird List (v 14.2). Doi 10.14344/IOC.ML.14.2. http://www.worldbirdnames.org/
- Brazil, M. A. 1991. The Birds of Japan. Smithsonian Inst. Press, Washington DC.
- Carboneras, C., Christie, D.A., Jutglar, F., Garcia, E.F.J. & Kirwan, G.M. (2019). Brown Booby (Sula leucogaster). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52625 on 5 October 2019).
- Howell, S. N. G. and K. Zufelt (2019) Oceanic Birds of the World: A Photo Guide. Princeton Univ. Press.
Recommended Citation
- BirdForum Opus contributors. (2025) Brown Booby. In: BirdForum, the forum for wild birds and birding. Retrieved 12 May 2025 from https://www.birdforum.net/opus/Brown_Booby
External Links
GSearch checked for 2020 platform.1
