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Philopatric predisposition to predation-induced ecological traps: habitat-dependent mortality of breeding eiders

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Author

  • Johan Ekroos
  • Markus Ost
  • Patrik Karell
  • Kim Jaatinen
  • Mikael Kilpi

Summary, in English

Because population size is sensitive to changes in adult survival, adult survival may be buffered against environmental variability. Philopatry may be adaptive in changing environments, but it could also constrain breeding habitat selection under changing conditions such as shifting predation regimes. Habitat preference and quality could become decoupled in long-lived philopatric species that evolved in stable environments when suddenly faced by increased adult predation risk, as dispersal may be triggered by past reproductive failure. We evaluated whether the Baltic eider (Somateria m. mollissima) population may currently face a predation-induced ecological trap. Eiders are philopatric and nest on open and forested islands. We hypothesized that open-nesting females would be disproportionately affected by increased predation. We compared female annual survival in these two habitats in 1996-2010. We also tested for effects of time trends, winter severity (NAO), female body condition, and habitat-specific predation pressure on survival. Our results revealed the lowest survival recorded for this species (I broken vertical bar = 0.720), and survival on open islands was significantly lower (I broken vertical bar = 0.679) than on forested islands (I broken vertical bar = 0.761). Nonetheless, only 0.7 % of females changed breeding habitat type despite ample availability of alternative islands, and breeding phenology in both habitats was similar. Female survival increased with body condition, while it was unrelated to winter climate and stable over time. Open islands had a higher predation pressure on incubating females. Breeding philopatry results in a predator-mediated ecological trap for open-nesting eiders. Our results contribute to explaining the drastic decline of the Baltic eider population.

Publishing year

2012

Language

English

Pages

979-986

Publication/Series

Oecologia

Volume

170

Issue

4

Document type

Journal article

Publisher

Springer

Topic

  • Biological Sciences

Keywords

  • Body condition
  • Habitat selection
  • Predation risk
  • Site fidelity
  • Survival analysis

Status

Published

ISBN/ISSN/Other

  • ISSN: 1432-1939