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Masked Booby Life History

Habitat

Habitat OceansMasked Boobies nest in colonies on tropical oceanic islands, usually flat islands that have little or no vegetation, unlike Red-footed Boobies (which nest in trees) or gannets (which favor cliffs). Masked Boobies will also nest in flat areas on the tops of cliffs, so long as there is not too much vegetation. They rest on islands, coral atolls, and human-made structures such as channel markers, pilings, oil drilling platforms, and large pieces of debris floating in the ocean. When not at the nesting area, Masked Boobies cross tropical seas in search of food.Back to top

Food

Food FishMasked Boobies eat mostly fish and squid, which they capture in dives from the air, sometimes plunging into the sea to take prey. They also capture flying fish, a favored prey item, in the air. In addition to flying fish, they eat jacks, blennies, milkfish, and even small tuna.Back to top

Nesting

Nest Placement

Nest GroundNests are set directly on the ground, usually in areas with no vegetation.

Nest Description

Nests consist of simple scrapes in the ground, usually adorned around the edges with small “gifts” that the male has presented to the female, such as sticks, pebbles, bits of vegetation, coral, or jetsam. Nests average about 20 inches across.

Nesting Facts

Clutch Size:1-2 eggs
Egg Description:Pale and unmarked
Condition at Hatching:Covered with very thin white down, unable to sit up.
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Behavior

Behavior Aerial Dive (water)As soon as Masked Boobies return to their breeding colonies, males claim a small patch of land and begin displaying, stretching their necks skyward and calling to attract a mate. If a female lands nearby, he may walk around her with exaggerated, high steps, showing off his feet, or present her with tokens, such as rocks or feathers. About half of pairs rejoin their mate from the previous breeding season and they maintain bonds by mutual preening of the neck and head feathers. Both adults share incubation and chick-rearing duties and defend their small nest area by pecking at or flapping their wings at others of their species that approach too closely, including chicks. Normally, they warn intruders with head-shaking movements before attacking, but if warnings fail, the attacks can seriously injure one or both birds involved. Masked Boobies also attack other seabirds that approach too closely but, in some colonies, nests are spaced well apart, and conflict is minimal. Because Masked Boobies reach adulthood at age 4 or older, younger birds that return to colonies tend to avoid nesting areas, instead hanging out in “clubs.”Back to top

Conservation

Conservation Low Concern

Partners in Flight estimates a global breeding population of 100,000 individuals and rates the species a 12 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. On some breeding islands, feral hogs, rats, and cats kill Masked Boobies, and the species is hunted for food by people in the Indian Ocean. People also harvest eggs at some colonies as well. It is likely that Masked Boobies, like other seabirds, are killed by commercial fishing activities such as purse-seine and longline operations.

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Credits

Grace, Jacquelyn and David J. Anderson. (2009). Masked Booby (Sula dactylatra), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2021.1. Patuxent Wildlife Research Center, Bird Banding Laboratory 2021.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Pitman, R. L. and J. R. Jehl. (1998). Geographic variation and reassessment of species limits in the "Masked" Boobies of the eastern Pacific Ocean. Wilson Bulletin 110 (2):155-170.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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