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Abstract
Climate change can impact on the survival of seabirds. While many studies have investigated the influences of climatic and oceanographic variables on seabird breeding, fewer have been able to capture the processes affecting survival. In this study, I carried out a mark-recapture analysis on a 46-year penguin dataset to study the effects of some climatic and oceanographic variables on the survival of little penguins Eudyptula minor in southeastern Australia. A priori knowledge of the birds' annual cycle and patterns of movement informed my selection of meaningful and biologically sensible variables.
Two age classes of penguins were considered, based on their differing patterns of movement: first-year birds and adult birds in their second and subsequent years of life.
The climatic and oceanographic variables considered in this study were wind strength, sea-surface temperature, east-west sea temperature gradient, air temperature, rainfall, humidity and chlorophyll a concentration. Climatic covariates which affected adult penguins on land had a direct impact on their survival, most likely via physiological stresses caused by climatic extremes. Oceanographic covariates had contrasting effects on first-year and adult penguin survival. Positive effects were most likely due to the movement of nutrients and associated prey into foraging areas as a result of favourable marine conditions, while negative effects were most likely due to a decrease in prey abundance, or physical factors such as changes in sea-surface temperature or turbulent seas, which affected prey availability or foraging behaviour.
The survival probabilities of first-year and adult birds were most strongly associated with different covariates, and at different times during the birds' annual cycle. The effects were not always immediate, with lagged covariates found to affect survival for both age classes. In a broader context, the effects of any single covariate on the distribution and demography of penguins may be correlated with, or masked by, a range of environmental conditions and interactions between covariates in the marine ecosystem. My research offers new insights into processes which affect penguin survival, and ultimately population security. The development of appropriate management and adaptation actions will further contribute to the conservation of seabirds.