MASKED BOOBY Sula dactylatra Lesson, 1831

This seabird occupies warm oceanic waters around the world, and in the eastern Pacific Ocean ranges to waters off Baja California Sur. Pitman and Jehl (1998) showed that yellow- and orange-billed birds, in what was collectively called the Masked Booby, behave as separate species in areas of sympatry. In splitting the species, they—and the AOU (2000)—retained the name Masked Booby (S. dactylatra) for the yellow-billed birds and called orange-billed birds the Nazca Booby (S. granti). Field identification appears to hinge on bill color, which starts to change from gray to either yellow or orange after one year of age (see the Masked/Nazca Booby account). After the split, the Committee reconsidered all accepted records of the Masked Booby (sensu lato) and now endorses as S. dactylatra only records of adults and subadults with distinctly yellow bills. California lacks a Masked Booby specimen, but the more likely subspecies is S. d. personata (including S. d. californica as a synonym; Pitman and Jehl 1998). Subspecies personata breeds in Hawaii, on islands off western Mexico, and on Clipperton Atoll (Howell and Pyle 1997). Adults of unknown subspecies at Isla Guadalupe between 20 January and 9 April 1994 (Pyle et al. 1994a, Guillén-H. et al. 1995) and at the Islas Los Coronados between 20 January and 6 April 2002 (NAB 56:226, 360) were north of the normal range.

California’s first Masked Booby was an adult recorded on 10 January 1977 approximately 22 nautical miles southwest of San Clemente Island, Los Angeles County (Lewis and Tyler 1978). Another decade passed before the next report of a bird from the Masked/Nazca Booby complex, but such records (including those reviewed in the following species account) began to pick up during the 1990s. Six CBRC-endorsed Masked Booby records are from late fall or winter (13 November–18 February), five are from late spring or summer (5 June–9 August), and one involves a bird seen periodically at San Clemente Island from 17 January 2003 through 15 August 2004 (see Appendix H).

Castillo-Guerrero et al. (2005) documented several leucistic Brown Boobies—birds with the mantle, scapulars, and lesser coverts white—in the Gulf of California and cautioned observers against mistaking such a bird for a Masked Booby. See also the 16 May 2006 photo of a suspected Masked Booby × Brown Booby hybrid from the Gulf of California off Sinaloa (NAB 60:445).

[NAZCA BOOBY Sula granti Rothschild, 1902]