Feeding and breeding ecology of Little Penguins (Eudyptula minor) in the Eastern Great Australian Bight.

Abstract

This thesis investigated aspects of foraging and reproductive ecology of little penguins Eudyptula minor in the eastern Great Australian Bight. Little penguins are permanent residents in this region and the link between their ecology and their local food source is poorly understood in the Great Australian Bight. Most little penguin colonies in South Australia are small in population (< 4000 breeding individuals) and they are almost all found on islands. Despite similarities in breeding seasons and diet among colonies, the foraging ecology of penguins from offshore colonies differed from inshore colonies in the same region. Natural variation in diet and foraging behaviour at eight colonies was attributed to differences in food availability. Inter-colony differences in foraging behaviour and effort, which were consistent between years, were related to differences in penguin morphology, growth and body size. Breeding penguins from the offshore colony travelled up to 3 times further from shore (39 vs. 13-21 km) and for greater durations (3 vs. 1 days), and spent more time diving (56 vs. 37 % of foraging time). Results suggest that food availability is depleted, or not profitable in near colony waters, possibly as a consequence of increased or prolonged predation by the large penguin population. This study also indicated that increased foraging effort at the colony level was reflected in the growth parameters of offspring, because offshore colonies had smaller offspring and adults, and delayed development of sexual size differentiation in bill morphology. Increases in foraging distance and duration were also linked to poorer breeding success. Little penguins at different colonies exhibited low variation in their diet because juvenile Australian anchovies Engraulis australis were mainly targeted as a food source. Dive behaviour was similar among colonies, despite differences in the depths around colonies. The regional availability and abundance of anchovies may be responsible for the unusual pattern of winter breeding that is apparent in South Australia. Little penguin diet, breeding and foraging parameters may provide quantitative indicators of the health of local anchovy stocks, especially if an anchovy fishery develops in South Australia. Baseline information on these penguin parameters parameters may also inform management decisions aimed at conserving penguin populations across the region.