Impacts of poor food food availability on positive density dependence in a highly colonial seabird

Ashbrook, Kate; Wanless, Sarah; Harris, Mike P.; Hamer, Keith C.. 2010 Impacts of poor food food availability on positive density dependence in a highly colonial seabird. Proceedings of the Royal Society B, 277. 2355-2360.

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For species with positive density dependence, costs and benefits of increasing density may depend on environmental conditions, but this has seldom been tested. By examining a colonial seabird (common guillemot) over a period of unprecedented poor food availability, we test two contrasting hypotheses suggesting that birds breeding at high density have: (i) greater leeway to increase foraging effort owing to more effective defence of unattended chicks against predators; and (ii) less leeway, owing to more attacks on unattended chicks by neighbouring adults. Supporting hypothesis 1, birds at high density increased provisioning rates and hence survival of chicks by foraging simultaneously with their partners, whereas at low density, unattended chicks were liable to be killed by predatory gulls and, unexpectedly, razorbills. Simultaneously, supporting hypothesis 2, heightened aggression towards unattended chicks at high density frequently resulted in infanticide, undermining benefits from collective defence against predators. Consequently, over 25 years, the magnitude of positive density dependence was independent of mean breeding success. These data indicate previously unsuspected trade-offs between costs and benefits of increasing density under changing environments. Previous generalizations about the importance of high density for reproductive success have so far remained robust, but such trade-offs could have unpredictable consequences for future population dynamics

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biodiversity > BD Topic 1 - Observations, Patterns, and Predictions for Biodiversity > BD - 1.3 - Long-term/large-scale monitoring and experiments ...
UKCEH and CEH Sections/Science Areas: Watt
UKCEH Fellows
ISSN: 0962-8452
Additional Keywords: chick neglect, colonial breeding, environmental change, Uria aalge, interference competition, social dynamics
NORA Subject Terms: Ecology and Environment
Date made live: 02 Aug 2010 09:35 +0 (UTC)

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