| Summary: | Tese de doutoramento em Biociências, ramo de especialização de Ecologia Marinha. apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra Trophic relationships are central in ecology and play a crucial role in species survival, as availability of food resources varies over time and space. The spatio-temporal variation in food sources at sea has many ecological implications on marine top predators such as seabirds. However, most ecological studies of resource use and population dynamics treat conspecific individuals as ecologically equivalent, but intra-specific variation in individual foraging strategies can be large and many apparently generalized populations are in fact composed of specialized individuals that use a small subset of the available resources over time (individual consistency). Studies on the incidence of individual specialization suggest that it may vary among species and among populations, but they are scarce, particularly for seabirds, and the mechanisms that generate inter-individual variation are not well understood. The main goal of this study is to corroborate the existence of individual specialization over time in three different species from four seabirds’ populations exploiting different marine environments. Furthermore, it investigates whether individual specialization is associated with the environment and resources exploited and assesses its ecological implications at the population and individual levels. The hypothesis of this thesis was tested using wandering albatross Diomedea exulans, Cory’s shearwater Calonectris diomedea and yellow-legged gull Larus michahellis as model seabird species, and fieldwork was conducted respectively in Bird Island (South Georgia, Antarctica), Corvo Island (Azores archipelago, Portugal) and Berlenga Island (Portugal). Two populations of Cory’s shearwater were studied, one from an oceanic environment (Corvo Island) and other from a neritic environment (Berlenga Island). A total of 199 birds were sampled during the breeding season of ...
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