ʻĀ
Masked Booby
Sula dactylatra

SPECIES STATUS:
SPECIES STATUS: State recognized as Indigenous Nature
Serve Heritage Ranking G5 - Secure
North American Waterbird Conservation Plan – Moderate concern
Regional Seabird Conservation Plan - USFWS 2005

The masked booby is the largest booby and, like its Hawaiian congeners, has a pantropical distribution. Four masked booby subspecies are recognized, and one of those three (S.d. personata) is a resident in Hawaiʻi. The hawaiian name, ʻā, is the same name shared with the other hawaiian booby congeners--the red-footed booby and the brown booby--due to their similar body characteristics such as beak, feet, tail, and relative size.

Individuals have long, pointed wings and a short, wedge-shaped tail. Adult males and females are overall white, except for a brownish black tail, black trailing wing edges, and black facial skin around the bill. Large bill varies in color from yellow to orange and is bright in males; females are larger than males.

Forages as far as 90 miles offshore alone or in large, mixed-species flocks associated with schools of large predatory fishes which drive prey species to the surface. They forage plung-diving from 100 feet over the water, often diving to about 12ft foraging for flying fish and jacks.

They return to breed at their natal colony to nest in dense colonies. On Kure, there are about 45 percent of nesting pairs remaining together through a second breeding season. Like the brown booby, there are two eggs that hatch asynchronistically. The first egg to hatch usually pushes the other sibling out of the nest. Breeding season is synchronous, eggs are laid between January and July with both parents share incubating, brooding, and feeding duties. They fledge about five months after they are hatched. Birds first breed at three to four years of age and the oldest known individual was 20 years old.

Distribution & Abundance

Masked booby nests mainly in NWHI with small colonies in MHI on Ka‘ula, Lehua, and Moku Manu. Outside the breeding season birds are most common near their breeding colonies, but individuals may wander thousands of kilometers from colonies.

Location & Habitat

Masked booby nests mainly in NWHI with small colonies in MHI on Ka‘ula, Lehua, and Moku Manu. Outside the breeding season birds are most common near their breeding colonies, but individuals may wander thousands of kilometers from colonies.