Environmental driven sexual segregation in a marine predator

• Main Author: Pereira, Justin da Silva
• Other Authors: Ramos, Jaime, Paiva, Vítor Hugo
• Format: Master Thesis
• Language: English
• Published: 2015
• Subjects: Segregação espacial; Experiência reprodutiva; Calonectris borealis; North Atlantic
• Online Access: http://hdl.handle.net/10316/30857

Dissertação de Mestrado em Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra. A knowledge of pelagic seabird foraging patterns is important to evaluate key areas for marine pelagic top predators. The main objective of this thesis was to describe the sex-driven foraging patterns of a pelagic top predator - Cory’s Shearwater, Calonectris borealis - breeding in the small island of Berlengas, Portugal, during the chick-rearing seasons of 2010-2014. We identified the environmental predictors that determine the selection of foraging areas by female and male Cory’s Shearwaters and the role of breeding experience in this process. This medium-term study also assessed, in a scenario of climate stochasticity, the ecological impacts of climatic conditions in marine environments and the possible change in the distribution of this species in the North Atlantic, considering the increase in sea surface temperature and given the vulnerability of seabird predators to extreme climatic events. We studied the foraging distribution of fifty-five male and female Cory’s shearwaters with GPS tracking devices during the chick-rearing period between 2010 – 2014, and accessed their trophic choices with stable isotope analysis (SIA) of their plasma. The study sample was also divided between experienced and inexperienced individuals using the total number of breeding attempts as a proxy for experience, and the prediction that reproductive success typically increases with breeding age and experience in seabirds. This study benefited from a long-term database of the breeding population, such that minimum age, sex and previous breeding experience were known for most of the individuals. We found spatial segregation of female versus male Cory’s Shearwaters as well as inexperienced versus experienced breeders, which increased during the last couple of years. Males relied heavily on static variables like the bathymetry of the area, while females were much more explorative, ...