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Brown Booby Sula leucogaster leucogaster 


brown boobies with chick

At a glance

Extirpated from at least 6-8 major historic colonies and this total may be closer to 20

In a number of existing colonies the number of pairs has declined by more than 50% in recent decades

Few studies conducted in West Indies region; and updated surveys of colonies needed


Many of the surviving colonies are difficult to access

Index


Identification:

Brown boobies are chocolate brown above and white bellied as adults. The brown extends down to upper breast and has a clear-cut division. Smaller than Masked Booby, Brown Boobies are 25-29 inches, 64-74 cm in total length.

Adults

Brown booby with white belly. Strong demarcated separation of brown and white plumage across lower breast. Plumages of sexes generally alike but females have greater mass than males.

Juveniles

Brown overall with underparts usually mottled brown and white. Demarcation across lower breast still apparent. These feathers shift to pure white over the first two years. Could be confused by inexperienced observers with immature Northern Gannets, or the other species of boobies.

Alternative Names

English: White-bellied Booby
French: Fou brun
Spanish: Boba prieta, Bubi chaleco.

Systematics

Four subspecies recognized. Sula l. leucogaster is the only subspecies in Atlantic Basin. Appears to be little gene flow between island groups.

Likely locations

Near nesting colonies, with individual non-breeding birds often seen within other seabird colonies.

Distribution

Pan-tropical in distribution, Nominate subspecies endemic to tropical Atlantic; breeds in the West Indies region, islands in the western Gulf of Mexico, and in the tropical Atlantic (Cape Verde, Ascension and islands off Brazil). Possibly nested formerly in Florida Keys.

Marine distribution primarily restricted to Caribbean and Gulf of Mexico and tropical Atlantic. This booby stays in the proximity of its breeding sites throughout the year. Storm blown individuals and vagrants occasionally along Southeastern Atlantic coast of United States.

Brown Booby Distribution

Biology

At sea

Adults feed closer to shore than other boobies, focus feeding in areas where nutrients concentrate. Diurnal. They feed by plunge diving (from 1-15 m above surface) and eat mostly flying fish and squid. Frequently in mixed species flocks and over foraging predatory fish (jacks or tuna). Follow fishing vessels to scavenge, or to capture fishes avoiding wakes of boats, often landing on rigging.

At the nest

Nest on the ground; today normally restricted to rocky cliffs, isolated cays and similar coastal predator-free sites. Like other boobies their nesting season varies from site to site. This is a result of seasonal food availability in adjacent waters and choosing nesting periods outside the hurricane season. Long lived; 26+ years (banding record of individual banded as adult). Life expectancy is 30-50 years. Defends territory within 1-5 m of nest. Constructs nest of available materials, often lined with finer vegetation. Egg pale bluish or greenish with chalky white outer layer. Clutch size 1-2, but only one chick is reared.  Incubation 40-44 days.  Fledging 95-120 days based on food availability. Continue to be fed by parents while learning to feed.

Current Population 

9784 Pairs in the Region with large concentrations in the Bahamas, the central Antilles, and islands of Venezuela and Colombian control within the Caribbean. Central American estimates are minimums because we have not received recent data. 

LocationColoniesBreeding Pairs
Bahamas101021
Turks and Caicos21
Cuba32
Cayman Islands3110
Jamaica2100
Navassa120
Dominican Republic3210
Puerto Rico81476
US Virgin Islands6572
British Virgin Islands4132
Anguilla42163
St. Maarten15
St. Bartholomew2160
Saba20
Antigua and Barbuda2150
Montserrat22
Guadeloupe5401
Dominica11
Martinique31
St. Vincent and the Grenadines4210
Grenada311
Trinidad and Tobago345
Venezuela12829
Colombia51000
Costa Rica150
Honduras11
Belize11
Total948674

Conservation Status

Atlantic population considered vulnerable, few nesting sites are protected, and loss of one or two of the larger breeding sites would represent an important segment of the existing population. Extirpated from numerous former nesting colonies. Considered Vulnerable (Schreiber and Lee 2000) and declining in West Indies.

Conservation Needs

Nearly all published biological studies have been conducted in other portions of the species range so little is known concerning local breeding phenology or dispersal.

It is somewhat paradoxical that boobies, known for their tameness, are actually quite vulnerable to human disturbance. To some degree it is this very tameness that encourages people to enter colonies and closely approach nesting birds. For unprotected nesting sites educational signage explaining the fragile nature of seabird nesting colonies, their importance and their vulnerability to disturbance would be helpful. Conservation programs, laws and enforcement are badly needed in the West Indies.

The trend of decreasing populations for all West Indies boobies suggest that all known colonies need to be protected and closely monitored. Goats and development are major conservation issues. Egging and human predation of adults still an issue in Jamaica. Major nesting sites need protection and, in that this boobies often nest in association with other seabirds, this protection would cover a number of at risk populations. Many colonies would benefit from regular patrols and key nesting islands should have seasonal wardens to prevent disturbance or the establishment of fishing camps.

Seabird colonies need to be identified by the individual governments and be given permanent protection from future development.

Photos

Selected References:

Schreiber, E. A. 2000. Status of Red-footed, Brown and Masked Boobies in the West Indies. Pages 46-57 in E. A. Schreiber and D. S. Lee (eds.) Status and Conservation of West Indian Seabirds. Society of Caribbean Ornithology, Special Publication Number 1. 225 pp.

Schreiber, E. A. and R. L. Norton. 2002. Brown Booby (Sula leucogaster). In The Birds of North America, No. 649 (A. Poole and F. Gill, eds.) The Birds of North America, Inc., Philadelphia.

West Indian Breeding Seabird Atlas by Will Mackin and David Lee is licensed under a
Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. Based on work at www.wicbirds.net. Permissions beyond the scope of this license may be available at www.wicbirds.net.

Suggested Citation: Lee, D. S., W. A. Mackin. 2009. Brown Booby. West Indian Breeding Seabird Atlas <http://www.wicbirds.net/brbo.html>. Last Updated: _____. Date accessed: ______.

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