MEPS 565:227-236 (2017)  -  DOI: https://doi.org/10.3354/meps12017

ABSTRACT: Niche partitioning plays an important role in minimising interspecific competition for resources. Using carbon and nitrogen stable isotopic analysis of feathers, we investigated how macaroni penguins Eudyptes chrysolophus and eastern rockhopper penguins E. chrysocome filholi breeding at the Prince Edward Islands partition the marine environment during the critical pre-moult period over 5 consecutive years (2011 to 2015). Both species consistently foraged immediately south of the Antarctic Polar Front, with macaroni penguins foraging farther south in years of reduced primary productivity, minimising spatiotemporal overlap between species. Macaroni penguins consistently foraged at a higher trophic level than rockhopper penguins, indicating trophic niche differentiation. Male rockhopper penguins fed at a higher trophic level than females, but macaroni penguins showed no differences between sexes. The observed dietary differences, partial allochrony and species-specific spatial responses to reduced primary productivity (i.e. prey availability) indicate that macaroni and eastern rockhopper penguins exhibit contrasting foraging strategies that limit interspecific competition during the pre-moult period.

KEY WORDS: Niche partitioning · Crested penguins · Stable isotopes · Pre-moult