Temporal variation in Adélie penguin diet at Béchervaise Island, east Antarctica and its relationship to reproductive performance

Abstract

Diet, and in particular, food quality and quantity can influence the reproductive performance of marine predators. Also, the diet of specialist predators is often monitored in programmes that model and manage ecosystems. We examined the diet of Adelie penguins (Pygoscelis adeliae), an important consumer of Southern Ocean living resources, at Bechervaise Island, east Antarctica, during the chick-rearing periods for 11 years between 1991–1992 and 2002–2003. We also investigated the relationship between diet and annual reproductive performance. Substantial inter- and intra-annual variation in both meal mass and composition was evident: adults generally returned with larger food loads during the creche compared with the guard stages, and diet composition was dominated by two prey types, krill and fish, which combined contributed to >90% of the diet by mass in 7 out of 11 years. Females generally brought back meals dominated by krill; males generally consumed fish-dominated meals. However, both sexes returned with a high proportion of krill when annual mean meal mass was also high, suggesting that more food was available in high krill years. There was also evidence that years of high reproductive performance were positively correlated with years of both high meal and krill mass. We believe that our results indicate that there is significant long-term inter- and intra-annual variability in the amount of food available to Adelie penguins and that this was reflected in their diet and measures of reproductive performance. Coupled with the observation that penguins did not switch prey, this indicates that Adelie penguins from Bechervaise Island are dependent predators of krill. This contrasts with populations in other locations but supports the notion that Adelie penguins are an informative species to monitor the management of Southern Ocean marine living resources in this region.