Diet of Eastern Pacific Brown Boobies Sula leucogaster brewsteri on Isla San Jorge, north-eastern Gulf of California, and an April comparison with diets in the middle Gulf of California

During 1998-2000 Eastern Pacific Brown Boobies Sula leucogaster brewsteri at Isla San Jorge fed on 30 prey species, including one squid, 14 small pelagic shoaling fishes and 15 benthic fishes. The data suggested that Pacific Anchoveta Cetengraulis mysticetus was the food item of choice. By comparing the diet of Brown Boobies at San Jorge with that at Isla San Pedro Martir and Isla San Ildefonso it seemed that availability of benthic fishes to the Brown Boobies at San Jorge, but not at San Pedro Martir and San Ildefonso, explains the longer breeding season and residence of this species at San Jorge.