Subtle but significant segregation in the feeding ecology of sympatric penguins during the critical pre-moult period
Résumé
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.