Growth Strategies in Blue Penguins Eudyptula minor minor

Abstract

This study of breeding Blue Penguins Eudyptula minor minor was undertaken in south-eastem New Zealand during 1982/83 and enabled quantitative analyses and comparisons of nestling growth rates of morphometric characters. Comparisons both within and between subspecies were used to assess the degree of variation in growth rates and breeding success. The logistic growth model best described E. minor growth with feet showing most rapid growth, followed by weight, flipper and bill respectively. It is suggested that the reason for rapid growth rates of feet and flippers in penguins is the necessity to maintain thermal balance. The subspecies of E. minor showed positive correlations between latitude and both asymptotic and adult weight and an inverse relationship between growth rate and asymptotic weight, but rates of increase in weight were not correlated with latitude. In th~s study E. m. minor experienced a fledging success of 75% but an egg success of only 47%. After comparison of reproductive performance in other subspecies, years and locations, it is suggested that brood reduction occurs in response to unfavourable conditions. In populations where extensive brood reduction occurred, the mean growth rates of E. minor nestlings were more rapid than in populations that experienced only limited reduction of broods.