NOTES: ANOMALOUSLY PIGMENTED BROWN BOOBIES IN THE GULF OF CALIFORNIA: LEUCISM AND POSSIBLY HYBRIDIZATION WITH THE BLUE-FOOTED BOOBY

Abstract

Plumage color anomalies in the Sulidae (boobies and gannets) seem to be uncommon and have received little attention in detailed studies of the family (Dorward 1962, Nelson 1978). The only reference to such anomalies in the Brown Booby (Sula leucogaster) is of an albino noted by Harrison (1983). Similarly, hybridization or mixed-species pairing among sulids has only rarely been reported; the only suspected cases involve the Brown and Masked (S. dactylatra) Boobies (Worcester, 1911, Nelson 1978), although the supporting evidence is weak. Here we report five leucistic Brown Boobies and two likely hybrids of Brown and Blue-footed (S. nebouxii) Boobies at Farallón de San Ignacio, northern Sinaloa, Gulf of California, México, during 2003 and 2004.