Importance of fisheries discards and experience for seabird behavior and energetics

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To exploit marine resources that are scattered patchily over large areas, and often unpredictable, albatrosses and petrels cover hundreds of kilometres per day and attend their chicks infrequently. In marine ecosystems with strong anthropogenic influences, the prey availability is often altered by the presence of fisheries vessels that produce large quantities of discards such as offal from processed fish, non-target species and undersized fish. Not only do they provide a predictable and abundant source of food to seabirds attending fishing vessels, but discards also facilitate access to demersal fish as a novel food source. In many fishery areas, discards thus contribute significantly to the diet of seabirds. This can have important implications on the seabirds foraging ecology. The aim of the present study is to enhance our understanding of behavioural adaptations in response to changes in prey availability, using a case study of Scopoli's shearwater in the Mediterranean Sea, a species that takes both natural prey and fisheries discards. To evaluate the extent and implications of fisheries discard consumption, we will use a combination GPS tracking, measurements of metabolic rates from acceleration logging, and non-invasive genetic diet determination. We will investigate whether the use of fisheries discard by the shearwaters occurs in response to low availability of their natural prey or if this species has adapted to regularly exploit this resource, independently of the availability of their natural prey. Moreover we will compare experienced and novel breeders so assess how the quality of adults influences this behaviour, and evaluate the energetic balance of natural prey and fisheries discard consumption.