Global change presents a unique threat to marine birds, who rely on both marine and terrestial environments at various points in their life histories. Change can effect these species through multiple biological pathways, both directly through changes to their environments and indirectly via trophic effects. For example, climate change affects sea surface temperatures, which alters prey population densities anddistributions. Egg size is a measure which is largely thought to correlate with maternal health and resource aquisition in birds, and thus provides an ideal metric for examining impacts of change on marine birds. Here, we combined a longitudinal dataset of egg size in the endangered northern rockhopper penguin (Eudyptes moseleyi) inhabiting the Tristan da Cunha islands with long-term data on climatic variables (e.g. sea surface temperature, sea level pressure) to investigate changes in penguin reproduction. In penguins, egg size is correlated with offspring size during the week after hatching, which may have effects on offspring survival. Contemporary and historical egg measurements from 1873 - presentprovide a viable method for evaluating changes in reproductive success on a large time scale and will allow us to examine observed population declines in this species. We regressed a variety of environmental variables on egg size and used a discriminate function created by Bond et al.(2016) to account for the effects of egg laying order. We used model selection to select the model that best explained the variation in the data.
Results/Conclusions