From fish to fowl : a comparison using stable isotope analysis of the little penguin [Eudyptula minor] in captive and wild populations.
Thesis DisciplineBiological Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
I collected moulted feathers from a captive group of little penguins [Eudyptula minor] over the course of two years for stable isotope analysis [SIA]. Diet was also sampled during this time, and I was able to connect the isotopic signatures of the food sources to that of the moulted feathers formed and thereby ascertain enrichment differences between diet and feathers. Feathers were also collected from three colonies of wild little penguins on the east coast of the South Island and from several sub-colonies on the West Coast. I used SIA of δ13C and δ15N of the feathers to determine whether trophic level depended on the geographic location of each colony. Relationships between the δ13C and δ15N stable isotope signatures of penguins from the wild colonies were then compared to the captive colony which comprised of individuals from around New Zealand. I next examined whether the “white-flippered penguin” [Eudyptula minor albosignata], a colour morph or subspecifies confined largely to Banks Peninsula, differed in stable isotope ratios from other populations. Finally, I also explored variation in isotopic signatures based on gender and geographic origin of the birds within the feathers produced by birds being fed on each diet/fish lot. I found that while the isotopic signatures of penguins fed on different lots of sprats were not significantly different in δ15N signatures, feathers produced on diet/fish lot 1 were different from other feather lots, and different from feathers produced from other diet/fish lots. There were no significant differences in either δ13C or δ15N isotopic compositions between penguins on the basis of their geographic origin in the captive population. Male and female birds also did not significantly vary in δ13C or δ15N when fed on an identical diet. Using δ15N, I found penguins on the West Coast occupied a lower trophic level than the east coast birds. Similar differences in the δ13C ratios also confirmed the birds on the two coasts were feeding on different prey species and were occupying different trophic levels. Surprisingly, a colony of the white-flippered morphs at Harris Bay was more similar in both δ13C and δ15N compositions to the more distant Oamaru population than to another, geographically closer, colony of the white-flippered morph in Flea Bay. My study confirms that SIA can be used to provide a general estimate of diet and analysis of feathers from wild populations could provide information on the diet [and trophic level] of free-living penguins. There was no difference between birds based on colony of origin when fed an identical diet, but there was variation between wild colonies, indicating that while diet influences the composition of the feathers, morphological differences do not. My study highlights the value of using SIA as a proxy for diet studies of wild seabirds.