Modeling the relationship between European storm petrel survival and environmental factors

Supervisors: Ana Sanz Aguilar, Daniel Oro de Rivas (Instituto Mediterráneo de Estudios Avanzados (IMEDEA))
Seabirds are potentially important indicators of the changing marine environment at large scales, owing to their long life-expectancy and integration of oceanic resources over wide areas. Adult survival has long been considered as a conservative demographic parameter in long-lived species. However, recent anthropogenic disturbances are affecting seabirds’ adult survival and promoting shifts in population dynamics. The European storm petrel Hydrobates pelagicus is the smallest Palearctic seabird, mostly affected by larger birds’ predation and extreme weather events (storms, gales). In this study, we used a multi-event capture-recapture modelling to assess the influence of environmental fluctuations on breeding adult mortality of storm petrels at one North-East Atlantic colony and two colonies on a Mediterranean island. Results suggested that the estimated mortality did not only differ between the two oceanic basins, but strikingly also between colonies on the same island. There was a temporal variability in adult mortality during breeding, linked to predation, which was an important driver of mortality in certain years (~0.05). Lower values of mortality at the sea were found in Mediterranean colonies (~0.10) compared to the Atlantic colony (0.18), which could be a result of a lower migration cost or more favourable conditions during wintering. Partial explanation of temporal variability in mortality at the sea (during wintering and migration) was given by St. Helena Island Climate Index for adults breeding at the Atlantic colony (15%), and the Western Mediterranean Oscillation index (WeMO) for breeders at the Mediterranean colonies (56% and 33% of variance for each of the two colonies, respectively). By the influence of these specific environmental factors, which could drive weather conditions and predator-prey relationships, we assume that North Atlantic individuals are wintering in South Atlantic, while Mediterranean individuals probably stay in the same basin. With future research orientated towards study of new approaches in detecting European storm petrel’s movements and foraging during both breeding and wintering, we expect a better application of climatic indexes, and thus an improvement of the understanding of the environmental impact on population dynamics of this species.