Influence of Extrinsic Factors on Movements and Reproductive Success of Leach's Storm-Petrel (Oceanodroma leucorhoa).
Small pelagic seabirds are valuable indicators of changes in marine ecosystems because they range widely and feed at low trophic levels, and so respond rapidly to changes in ocean conditions. Globally, rapid climatic changes and increased pollution are changing marine environments. Determining how foraging and migratory movements in the face of these changes affect reproductive success of pelagic seabirds allows for a better understanding of the state of ocean ecosystems. However, until a decade ago, it was difficult to track smaller species (< 100 g). The objective of my thesis was to evaluate extrinsic factors influencing the reproductive success of small procellariform seabirds, using the Leach’s storm-petrel (Oceanodroma leucorhoa) as a model species. In Chapter 2, I tracked movements of Leach’s storm-petrels from two colonies in Nova Scotia during the incubation period, to determine what ocean conditions they faced. In Chapter 3, I evaluated ocean conditions associated with reproductive success during the breeding season. In Chapter 4, I described migratory patterns and ocean conditions in wintering areas. Finally, in Chapter 5, I evaluated effects of mercury, a neurotoxin present globally in marine ecosystems, on reproductive success. Results indicated that during the incubation period Leach’s storm-petrels foraged about 800 km from their breeding colonies, beyond the continental shelf, further than expected based on allometry. High sea-surface temperatures during the breeding season and a high North Atlantic Oscillation index were negatively associated with storm-petrel reproductive success, probably through indirect effects on prey abundance. Migration patterns were variable across individuals, but I found that storm-petrels used the productive waters of the Equatorial and Benguela Currents as wintering areas. Finally, there was no association between mercury concentrations and storm-petrel reproductive success. Overall, my results suggested that extrinsic factors associated with climate change, changing sea-surface temperature and the North Atlantic Oscillation index, are likely to have negative effects on the reproductive success of Leach’s storm-petrels. Climate projections suggest the Scotian Shelf will continue warming and the North Atlantic Oscillation index will mostly be positive, which is worrying for North Atlantic seabirds. My research serves to predict seabird responses to environmental change by linking extrinsic factors to reproductive success.