Sexual segregation in spatial and feeding ecology of seabirds
- Autores: Fernanda Pereira de Felipe
- Directores de la Tesis: Jacob González-Solís i Bou (dir. tes.), Raúl Ramos García (codir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2020
- Idioma: inglés
- Tribunal Calificador de la Tesis: Paulo Catry (presid.), Lluís Cardona Pascual (secret.), Joan Navarro Bernabé (voc.)
- Programa de doctorado: Programa de Doctorado en Biodiversidad por la Universidad Autónoma de Barcelona y la Universidad de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
Sexual segregation (SS) is a phenomenon that occurs across a wide range of animal species, with sexes segregating in spatio-temporal distribution, behaviour or feeding ecology. For pelagic seabirds, most studies on SS to date have focused on the breeding period, but the extent of SS and implications in relation to environmental conditions and fisheries, and its occurrence during the non-breeding period, remains poorly understood. We aimed to understand the causes and consequences of SS in spatio-temporal distribution, migratory phenology, behaviour and feeding ecology of three closely-related shearwaters: Scopoli’s, Cory’s and Cape Verde shearwaters (Calonectris diomedea, C. borealis and C. edwardsii, respectively). We assessed potential sexual differences during breeding (only for Scopoli’s shearwater) and non-breeding periods and discussed whether they persist throughout the annual cycle, and their main drivers. Our results revealed that during the breeding period, females of Scopoli’s shearwater seem to be outcompeted by males and forced to increase their foraging effort, especially under unfavourable conditions. Furthermore, we tested for sexual differences in fishing vessel attendance and found that males interacted with fishing vessels to a greater extent, profiting from discards more than females. This indicates that SS in foraging strategies of Scopoli’s shearwater may lead to unbalanced exposure of males and females to bycatch in the North-Western Mediterranean, which could reduce effective population size and compromise population viability of the species. During the non-breeding period, both sexes of the three Calonectris shearwaters share the same non-breeding areas, suggesting competitive exclusion does not promote spatial segregation throughout the annual cycle. Sexual differences in the migratory phenology were subtle for the three species, with males consistently returning earlier to the breeding colonies, and male Cory’s shearwaters remaining resident in a larger proportion than females, likely due to sex-specific reproductive roles at early stages of the breeding period. For both breeding and non-breeding periods, sexes consistently feed on different trophic levels, suggesting that sexual differences in diet may persist year-round. Overall, we found consistent differences in foraging movements, migratory phenology, and resource use between sexes, indicating a robust SS during breeding and non-breeding periods in shearwater species.
