Brown Booby

Sula leucogaster

Order PELECANIFORMES - Family SULIDAE

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1. Cool Facts
2. Description
3. Similar Species
4. Sound
5. Range
6. Habitat
7. Food
8. Behavior
9. Reproduction
10. Conservation Status
11. Other Names

A widespread seabird of tropical waters, the Brown Booby ranges as far north as the Gulf of California, and rarely to both coasts of the United States. Like other boobies, it feeds with spectacular plunges into the sea.

Cool Facts

• The Brown Booby is the only ground-nesting booby that regularly builds a substantial nest.
• Like all boobies and pelicans, the Brown Booby's feet are "totipalmate," having webbing connecting all four toes.

• Brown Booby nests sometimes contain the bodies of dead Sooty Tern chicks.

• Male and female Brown Boobies generally look alike in plumage color, except in populations found along the Pacific Coast of Mexico and Central and South America. There the females look like those in other populations, but the males have light gray to white heads.

Description

• Size: 64-85 cm (25-33 in)
• Wingspan: 132-155 cm (52-61 in)
• Weight: 950-1800 g (33.54-63.54 ounces)

• Large, dark waterbird.
• Long body, long neck, long tail.
• Narrow, pointed wings.
• Brown head, throat, chest, and upperparts.
• White belly, vent, and wing linings

• Long bill.
• Silhouette appears straight, with head and neck sticking out beyond wings as far as tail sticks out backwards.
• Sharp separation of brown and white on chest.
• Colors of bare parts vary by region, sex, age, and time of year.
• Adult male usually has blue skin around eyes.
• Bill and feet may be bright yellow, pink, or grayish.

Sex Differences

Sexes similar. Female larger than male. Male's facial skin is usually blue, whereas female's is yellow.

Immature

Juvenile is brown overall; belly ranges from mottled brown and white to mostly dark. Sharp line still visible between darker chest and lighter belly. Underwing coverts are pale. Bare parts generally dull gray.

Similar Species

• Adult Brown Booby is easily distinguished from other adult boobies by its sharp border between dark brown chest and white belly.
• Juvenile Masked Booby resembles adult Brown Booby, but has white lower neck and chest.
• Red-footed Booby juvenile is also mostly brown, but its underwing coverts are all dark and upperwing shows white in wrist area when feathers are worn.
• Immature Northern Gannet can have dark head and neck and paler chest, but the separation usually is not sharp. Gannet has feathering in front of eyes, boobies do not.

Sound

At breeding colony, female issues a loud honk. Male makes a high-pitched whistling sound.

Range

Summer Range

Breeds in tropical waters throughout the world, approximately 30° N latitude to 30° S.

Winter Range

Distribution outside of breeding season is unclear. Some Brown Boobies range hundreds or thousands of miles from their breeding colonies.

Habitat

Nests on islands, covering a wide range of vegetation types, geologic features, and weather patterns. Found at sea in nonbreeding season.

Food

Squid and fish, especially flying fish.

Behavior

Foraging

Plunge-dives from various heights up to 15 m (50 feet). Folds wings next to body at beginning of dive, then thrusts wings straight out over back, touching in the middle, just before breaking the surface. Dive may reach just below surface, or to as much as 2 m (6 feet) deep. Commonly feeds in areas where large predatory fish such as tuna drive smaller fish to the surface. Also follows fishing vessels.

Reproduction

Nest Type

Mound of branches, bones, grass, human-generated trash, or other items. Placed on flat ground, usually in full sunshine. Nests in colonies.

Egg Description

Pale bluish or greenish, with white outer layer.

Clutch Size

Usually 1-2 eggs. Range: 1-3.

Condition at Hatching

Blind and helpless.

Conservation Status

No longer breeds on many tropical islands where predators have been introduced. Human population growth and development of islands have caused severe population declines over the past century in the Caribbean.

Other Names

Fou brun (French)
Boba prieta, Bubi chaleco (Spanish)
White-bellied Booby (English)

Sources used to construct this page:

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, PA.