Brown Booby (Sula leucogaster)

[order] Pelecaniformes | [family] Sulidae | [latin] Sula leucogaster | [UK] Brown Booby | [FR] Fou brun | [DE] Weissbauchtolpel | [ES] Piquero Pardo | [IT] Sula fosca | [NL] Bruine Gent

Subspecies

Physical charateristics

The Brown Booby is a medium-large seabird characterized by dark brown coloration except on the breast, abdomen and underwing, which are white in the adult. Immatures are entirely dusky brown. Females are larger than males, but in the Virgin Islands sexes can be distinguished by bill color (pinkish-yellow in females, greenish-yellow in males) and vocalizations (females honk, males whistle). The genus Sula is from the Icelandic word
Sulan, meaning ?an awkward fellow?. The name ?booby? comes from the Spanish word bobo, which means ?stupid fellow? referring to the bird?s lack of fear of man and clumsiness on land making them easy to catch. Although awkward on land, their cigar-shaped bodies and narrow wings reflect a superb aerodynamic design, which is specially adapted for plunge-diving. Their dagger-shaped bill is long and pointed with serrated edges, ideal for swift seizure and grasping of slippery fish. The external nostrils are closed, but secondary nostrils beside the mouth are covered by moveable flaps when the bird plunge-dives into the sea. A semitransparent third eyelid closes to protect the eyes in bad weather and underwater. The feet are totipalmate (webbed between all four toes) to help the birds to swim well. They have strong skulls and rib cages to withstand the pressure of diving into the water. Air sacs under the skin also help to cushion the blow when diving for fish.

Listen to the sound of Brown Booby

[audio:http://www.aviflevoland.nl/sounddb/B/Brown Booby.mp3]

Copyright remark: Most sounds derived from xeno-canto

Range

Worldwide in tropical seas; summer visitor to the Gulf coast and Caribbean Sea; casually farther north in western Atlantic; occasionally seen in southern California?s Salton Sea; accidental along Pacific coast. Pelagic, breeds on coastal islands. Very rare vagrant in Suriname.

Habitat

Brown booby is found in mapped marine range all year. In fact, it refers to nearly offshore islands. We can find it in rocky islands and surrounding waters, also inshore waters of mainland coasts, less often offshore waters. It winters at sea over a wider area.

Reproduction

Like most seabirds, boobies are characterized by long lifespans (20 years or more), low reproductive rates, slow chick growth and delayed maturity. Nesting can occur during any time of the year. Brown Booby nests are placed on the ground and are constructed of grasses and occasionally seaweed. Like the Masked Booby, Brown Boobies usually lay two eggs but raise only one chick to maturity. Incubation begins when the first egg is laid, resulting in the first chick being considerably larger and stronger than the second. It is for this reason that the second smaller chick is usually the one that does not survive. Both sexes take turns incubating the eggs and caring for the young chick. Incubation lasts about 42 days and because brood patches are absent, boobies use the webs of their feet, which are extensively vascularized, to transmit essential heat to the eggs. Once hatched, chicks take about 100 days to fledge and are fed an additional 6 weeks at the nest site by the parents. Boobies feed their young directly from the adult?s throat. Those chicks that survive spend several years away from the colony before returning, usually to the colony of their birth, to breed. Like most seabirds, boobies are characterized by long lifespans (20 years or more), low reproductive rates, slow chick growth and delayed maturity. Nesting can occur during any time of the year. Brown Booby nests are placed on the ground and are constructed of grasses and occasionally seaweed. Like the Masked Booby, Brown Boobies usually lay two eggs but raise only one chick to maturity. Incubation begins when the first egg is laid, resulting in the first chick being considerably larger and stronger than the second. It is for this reason that the second smaller chick is usually the one that does not survive. Both sexes take turns incubating the eggs and caring for the young chick. Incubation lasts about 42 days and because brood patches are absent, boobies use the webs of their feet, which are extensively vascularized, to transmit essential heat to the eggs. Once hatched, chicks take about 100 days to fledge and are fed an additional 6 weeks at the nest site by the parents. Boobies feed their young directly from the adult?s throat. Those chicks that survive spend several years away from the colony before returning, usually to the colony of their birth, to breed. Like most seabirds, boobies are characterized by long lifespans (20 years or more), low reproductive rates, slow chick growth and delayed maturity. Nesting can occur during any time of the year. Brown Booby nests are placed on the ground and are constructed of grasses and occasionally seaweed. Like the Masked Booby, Brown Boobies usually lay two eggs but raise only one chick to maturity. Incubation begins when the first egg is laid, resulting in the first chick being considerably larger and stronger than the second. It is for this reason that the second smaller chick is usually the one that does not survive. Both sexes take turns incubating the eggs and caring for the young chick. Incubation lasts about 42 days and because brood patches are absent, boobies use the webs of their feet, which are extensively vascularized, to transmit essential heat to the eggs. Once hatched, chicks take about 100 days to fledge and are fed an additional 6 weeks at the nest site by the parents. Boobies feed their young directly from the adult?s throat. Those chicks that survive spend several years away from the colony before returning, usually to the colony of their birth, to breed. They nest in colonies.

Feeding habits

Brown Boobies are primarily inshore feeders. They feed on flying fish, squid,
and a variety of smaller baitfish. Boobies are powerful high-speed soaring birds that can torpedo after a flying fish or fall straight down like a falcon. Seabirds have the ability to drink salt water by using a specialized salt gland located behind the orbit of the eye. The salt gland allows the booby to excrete excess salt through the nasal passages which is eliminated by shaking the head. Feeding aggregations of boobies are of considerable
economic importance to sport and commercial fishermen as beacons for locating pelagic fish schools.

Conservation

This species has a large range, with an estimated global breeding Extent of Occurrence of 50,000-100,000 km². It has a large global population estimated to be 200,000 individuals (M. Crosby in litt. 2003). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.

Migration

Adults tend to stay more or less permanently around colony. Young and non-breeders disperse widely, and some records of inter-colony movements.

Distribution map

Literature

Title FIRST ATLANTIC RECORDS OF THE RED-FOOTED BOOBY SULA SULA AND BROWN BOOBY S. LEUCOGASTER IN SOUTHERN AFRICA

Author(s): DYER, B.M. & Y. CHESSELET

Abstract: The Red-footed Booby Sula sula and the Brown Booby..[more]..

Source: Marine Ornithology 30: 36-37

Title PSEUDO-EGGS OF BROWN SULA LEUCOGASTER AND BLUE-FOOTED S. NEBOUXII BOOBIES IN THE GULF OF CALIFORNIA, MEXICO

Author(s): MELLINK, E.

Abstract: Pseudo-eggs, foreign round objects, notably eggs o..[more]..

Source: Marine Ornithology 30: 43-44

Title DNA FINGERPRINTING AND PARENTAGE IN MASKED (SULA
DACTYLATRA) AND BROWN (S. LEUCOGASTER) BOOBIES

Author(s): Melina Martha Baumgarten et al.

Abstract: Masked Booby (Sula dactylatra) and Brown Booby (S…[more]..

Source: ORNITOLOGIA NEOTROPICAL 12: 319-326, 2001