Abbott's booby

Papasula abbotti

TAXONOMY

Sula abbotti, Ridgway, 1893, Assumption Island. Monotypic.

OTHER COMMON NAMES

French: Fou d'Abbott; German: Abbott-Tölpel; Spanish: Piquero de Abbott.

PHYSICAL CHARACTERISTICS

31 in (79 cm); 3.2 lb (1.46 kg). Distinctive shape with long, narrow wings. White underparts, neck and head; upperparts dark-brown. Bill slightly hooked and highly serrated, pinkish in female, blue-gray tinged pink in male.

DISTRIBUTION

Breeding currently confined to Christmas Island (Indian Ocean) from where it disperses widely for foraging. Formerly more widespread across Indian Ocean, east to western Pacific.

HABITAT

Strictly marine and pelagic. Nesting is restricted to tall forest trees in central plateau of Christmas Island. Foraging area not precisely known, but frequently seen in rich upwelling area off Java, often well away from nearest land.

BEHAVIOR

Nesting site on trees high above ground affects territorial and pair behavior, so Abbott's boobies' displays are the least fervent of all sulids. Territorial disputes are unknown in this species and even chick begging behavior is moderate in comparison with that of its congeners.

FEEDING ECOLOGY AND DIET

Not precisely known. Thought to prey mostly on flying-fish and squid. Forages well away from nesting island and presumably feeds by plunge-diving like other members of the family.

REPRODUCTIVE BIOLOGY

Fairly seasonal (laying in May through July.) but only a biennial breeder when successful. Very low reproductive success, mainly due to coincidence of breeding season with monsoons. Nest is platform of twigs and sticks high above ground; only loosely colonial. Lays only one egg, which is incubated for 57 days (longest of all sulids). Chicks fledge at 140–175 days. Post-fledging care period is also very long: 162–280 days. Does not breed until four to six years old.

CONSERVATION STATUS

Critically Endangered (BirdLife International, 2000), due to extremely reduced breeding range and small, declining population of only 2,500 active pairs as of 2000. Most highly threatened by ecological alterations on breeding island caused by introduced yellow crazy ant (Anoplolepis gracilipes), which is known to prey on chicks, as well as to kill the red crab (Gecaroidea natalis), and to farm scale insects which damage the trees. A control program for this ant has been initiated. In the past, mining of Christmas Island for phosphate extraction has reduced nesting habitat significantly. Destruction of rainforest on former breeding islands is thought to have caused their extirpation.

SIGNIFICANCE TO HUMANS

None known. Abbott's booby's secretive habits have resulted in few interactions between this species and humans.