Environmental drivers of sex-biased foraging behavior in Magnificent Frigatebird in Baja California Sur, Mexico

Understanding the characteristics of a species's distribution represents a challenge in marine environments because movement patterns and foraging areas are restricted by highly dynamic spatiotemporal variations in environmental conditions. In response to this heterogeneous context, marine predators such as seabirds need to maximize their foraging efficiency, especially during the breeding season, when movement is restricted by the need to return to the nest. Biologging technologies such as satellite transmitters and Global Positioning System (GPS) receivers allow researchers to track birds at sea and investigate the relationship between foraging strategy and changing oceanographic features. Our study focuses on characterizing the feeding areas of Magnificent Frigatebird (Fregata magnificens) breeding in Baja California Sur, Mexico. We used GPS receivers to track the foraging flights of frigatebirds during 2017-2019, identifying the core foraging areas and characterizing environmental conditions and marine productivity in these areas. Individuals repeatedly selected areas close to the colonies located in Espiritu Santo archipelago (Gulf of California) and Santa Margarita Island (Pacific Ocean). However, some males flew to more distant and equally productive areas to the south and north of the Baja California peninsula. We presume that the differential use of foraging areas between males and females reflects biometrical and behavioral differences of the sexes, which may explain the relationships between foraging behavior and breeding, intraspecific competition, and sex-based differences in parental investment. Because frigatebirds are considered indicators of marine environmental conditions, our data are useful to identify areas where prey species aggregate in space and time and, therefore, to expand the boundaries of existing marine protected areas. Data on seabird foraging ranges described here can be useful for delineating marine protected area boundaries and can be considered suitable candidates for inclusion in appropriately designated regional marine spatial planning.