- 29.1–33.9 in
- 63 in
- 45.9–82.9 oz
- Blue-faced Booby, White Booby
- Fou Masqué (French)
- Piquero enmascarado (Spanish)
- The population of Masked Boobies breeding along the Pacific Coast of northern South America, including the Galapagos, was recently recognized as a separate species, the Nazca Booby. The Nazca Booby has an orange, not yellow, bill and is smaller with a significantly shorter, shallower bill. Whereas the Masked Booby usually nests on low, flat areas, the Nazca Booby uses cliffs and steep slopes.
- Although the Masked Booby regularly lays two eggs, it never raises two young. The first egg is laid four to nine days before the second, and the older chick always ejects the second from the nest. The parents do not protect or feed the ejected chick, and it is quickly scavenged by a host of associated crabs, landbirds, and frigatebirds.
- The oldest recorded Masked Booby was at least 25 years, 3 months old when it was found alive in the wild in the Pacific Oceania area.
Nests on small tropical islands, especially ones that are flat and without forests. Spends rest of time at sea.
Fish and squid.
- Clutch Size
- 1–2 eggs
- Egg Description
- Light blue.
- Condition at Hatching
- Nearly helpless, with sparse white down.
Slight depression on ground, surrounded by circle of pebbles or other debris, often near a breezy cliff edge or other take-off feature
Plunge-dives from various heights up to 30 meters (100 feet) into schools of fish.
There 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.
- Anderson, D. J. 1993. Masked Booby (Sula dactylatra). In The Birds of North America, No. 73 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union
- Kushlan, J.A., et al. 2002. Waterbird conservation for the Americas: the North American Waterbird Conservation Plan, version 1. Waterbird Conservation for the Americas. Washington, DC.
- North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014 Report. U.S. Department of Interior, Washington, DC.
- Pitman, R. L., and J. R. Jehl, Jr. 1998. Geographic variation and the reassessment of species limits in the "Masked" Boobies of the eastern Pacific Ocean. Wilson Bulletin 110: 155-170.
- USGS Patuxent Wildlife Research Center. 2015. Longevity records of North American Birds.