Year-round at-sea distribution and trophic resources partitioning between two sympatric Sulids in the tropical Atlantic

by Nathalie Almeida, Jaime A. Ramos, Isabel Rodrigues, Ivo dos Santos, Jorge M. Pereira, Diana M. Matos, Pedro M. Ara újo, Pedro Geraldes, Tommy Melo, Vitor H. Paiva In the oligotrophic tropical marine environment resources are usually more patchily distributed and less abundant to top predators. Thus, spatial and trophic competition can emerge, especially between related seabird species belonging to the same ecological guild. Here we studied the foraging ecol ogy of two sympatric species–brown booby (BRBO)Sula leucogaster (breeding) and red-footed boobies (RFBO)Sula sula (non-breeding) –at Raso islet (Cabo Verde), across different seasons. Sexual segregation was only observed during Jun-Oct, when RFBO were present, with larger females BRBO remaining closer to the colonies, while males and RFBO travelled further and exploited different habitats. Overall, species appeared to prefe r areas with specific oceanic features, particularly those related with oceanic currents and responsible for enhancing primary productivity in tropical oceanic areas (e.g. Sea Surface Height and Ocean Mixed Layer Thickness). Female BRBOs showed high foraging-site fidelity during the period of sympat ry, while exploiting the same prey species as the other birds. However, during the months of co-existence (Jun.-Oct.), isotopic mixing models suggested that female BRBO would consume a higher proportion of epipelagic fish, whereas female RFBO would consume more squid compared to the other birds, pos...
Source: PLoS One - Category: Biomedical Science Authors: Source Type: research