The comparative foraging ecology of Royal Eudyptes schlegeli and Rockhopper E. chrysocome Penguins
Penguins are well adapted to the marine environment, spending the majority of their time at sea. Whilst their ecology is intrinsically linked to this environment, details of how they interact with biotic and abiotic aspects of it are not well known for most species. The majority of penguins have a l...
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| Format: | Thesis |
| Language: | unknown |
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1997
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| Online Access: | https://doi.org/10.25959/23206895.v1 https://figshare.com/articles/thesis/The_comparative_foraging_ecology_of_Royal_Eudyptes_schlegeli_and_Rockhopper_E_chrysocome_Penguins/23206895 |
| Summary: | Penguins are well adapted to the marine environment, spending the majority of their time at sea. Whilst their ecology is intrinsically linked to this environment, details of how they interact with biotic and abiotic aspects of it are not well known for most species. The majority of penguins have a limited breeding season, and commitments at the nest necessitate that their foraging ranges are restricted, presumably placing pressure on prey resources around nesting colonies. Sympatrically breeding species are thought to compete for these resources, and their co-existence is thought possible by the segregation of aspects of their ecologies, in particular foraging zones, diet or the asynchrony in breeding timetables. Royal and Rockhopper Penguins both belong to the Eudyptes genus, are ecologically very similar, and breed sympatrically on Macquarie Island. This similarity provides the opportunity to explore the issue of ecological segregation in these two species. The purpose of this study was to describe the foraging ecology of Royal and Rockhopper Penguins and to determine the degree of overlap in resource use. It was undertaken over three years (1993/4, 1994/5 and 1995/6) to examine inter-annual variability. The thesis is divided into two parts, the first dealing with methodological aspects. Morphometric indices were determined for externally sexing birds in the field. Bill length and depth were found to be reliable measures for sexing individuals of both species. Experiments assessing the impact of investigators on breeding success found no significant effects, provided care was taken when working in the colony. The deployment of external devices (transmitters and Time Depth Recorders, TDRs) was an integral part of data collection in the study, and the impact of these on Royal Penguins was examined: No effects were found in birds carrying the small, streamlined VHF transmitters, but the attachment of the larger, unstreamlined TDRs decreased the likelihood that penguins would return from a foraging trip, increased ... |
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