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Merlin Bird ID

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    Masked Booby Life History


    Habitat OceansNests on small tropical islands, especially ones that are flat and without forests. Spends rest of time at sea.Back to top


    Food FishFish and squid.Back to top


    Nest Placement

    Nest Ground

    Nest Description

    Slight depression on ground, surrounded by circle of pebbles or other debris, often near a breezy cliff edge or other take-off feature

    Nesting Facts
    Clutch Size:1-2 eggs
    Egg Description:Light blue.
    Condition at Hatching:Nearly helpless, with sparse white down.
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    Behavior Aerial Dive (water)Plunge-dives from various heights up to 30 meters (100 feet) into schools of fish.Back to top


    Conservation Low ConcernThere is little information on Masked Booby population trends, but it appears to be a species in decline. The North American Waterbird Conservation Plan estimates a continental breeding population of 80,000-120,000 birds, rates the species a 13 out of 20 on the Continental Concern Score, and lists it as a Species of High Concern. Masked Booby is on the 2014 State of the Birds Watch List, which lists bird species that are at risk of becoming threatened or endangered without conservation action. There is at least some mortality from tangling in fishing gear, but this problem is not known to be significant. These birds probably have frequent interactions with purse-seining tuna fisheries, as the fisheries often use Masked Boobies and other seabirds to locate tuna schools, but no data exist.Back to top


    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, D.C.: Waterbird Conservation for the Americas.

    Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

    North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

    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 no. 110 (2):155-170.

    Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

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