At sub-Antarctic Marion Island, annual breeding success of macaroni (Eudyptes chrysolophus) between 1979/80 and 1995/96 and rockhopper penguins (E. chrysocome) between 1985/86 and 1995/96 was measured. For macaroni penguins, averages of 0.48 eggs and 0.35 chicks were hatched and fledged respectively for each clutch laid. Corresponding averages for rockhopper penguins were 0.68 eggs and 0.48 respectively. The largest of the three macaroni penguin colonies investigated decreased in size over the study period, while the other two remained stable. The only significant relationship between inter-season trends in the number of pairs breeding at the three colonies was a negative correlation between two adjacent colonies, which suggests inter-colony transfer. The larger two of the three rockhopper penguin colonies investigated decreased over the study period, while the other remained stable. Trends in the number of pairs breeding at the three rockhopper penguin colonies were all significantly correlated. The proportion of rockhopper penguins attempting to breed may have varied as a result of some environmental signal. Inter-season trends in breeding success of macaroni penguins were significantly correlated in all three inter-colony comparisons over the entire study period. Inter-season trends in breeding success and chick survival of rockhopper penguins were significantly correlated in only one of the three inter-colony comparisons. The greater coherence in the performance of macaroni penguin compared to rockhopper penguin colonies suggests that breeding success of macaroni penguins may be influenced by a wider-scale phenomenon than is applicable to rockhopper penguins. Trends in breeding success, hatching success and chick survival of macaroni penguins and rockhopper penguins were not significantly correlated to each other, even for nearby colonies. This suggests that factors influencing the reproductive performance of the two species are not the same.
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