Sula dactylatra, Lesson, 1831, Ascension Island. Five subspecies generally recognized: S. d. dactylatra , Lesson, 1831; S. d. melanops, Heuglin, 1859; S. d. personata, Gould, 1846; S. d. fullagari, O’Brien and Davies, 1990; S. d. granti, Rotschild, 1902.
OTHER COMMON NAMES
English: Blue-faced booby, white booby; French: Fou masquй; German: Maskentцlpel; Spanish: Piquero Enmascarado.
31.9–36.2 in (81–92 cm); wingspan 59.8 in (152 cm). Largest of all boobies, body feathers mostly white; flight and tail feathers black. Bare parts mostly dark, bill usually yellow in males, duller in females. Females average slightly larger in size.
Pantropical, race dactylatra occurs in Caribbean and Atlantic; melanops in west Indian Ocean; personata in east Indian Ocean and central Pacific; fullagari in north Tasman Sea; granti in east Pacific.
Strictly marine and fairly pelagic, prefers more offshore waters than other booby species. Nests on bare ground and cliffs on rocky offshore islands.
Breeds in less dense colonies than other boobies. Accordingly, defends nest site less tenaciously and whole
is less aggressive. Much territorial
is based on ritualized displays. Pair-bonding
is also less intense than in other species.
FEEDING ECOLOGY AND DIET
Feeds mostly on shoaling fish, especially flying-fish, which it catches by plunge-diving from great heights. Feeds farther offshore than other species, also taking larger prey.
Only loosely colonial, very simple nest of accumulated excreta on cliff, slope or flat ground. Usually lays two eggs; brood size subsequently reduced to one chick through sibling aggression. Incubates eggs for 44 days. Chick fledges at 120 days and is further cared for another 156 days. Does not breed until two to three years old.
Not threatened. Much widespread and locally abundant, total population may number several hundred thousand individuals. Known to have undergone some declines locally, particularly as a consequence of predation by introduced animals. Eggs and chicks also taken for food locally. Booming tourist industry may pose further threat.
SIGNIFICANCE TO HUMANS
Subject to a moderate degree of exploitation for food, perhaps also for fish-bait. Some breeding colonies may be of interest for local tourist industry.
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