Effects of decreased anthropogenic food availability on an opportunistic gull: evidence for a size‐mediated response in breeding females

Emma C. Steigerwald*, José Manuel Igual, Ana Payo-Payo, Giacomo Tavecchia

*Corresponding author for this work

Research output: Contribution to journalArticle

25 Citations (Scopus)


Some opportunistic vertebrates exploit, and may largely rely upon, food generated by human activities. Better understanding the influence of this additional anthropogenic food on species' ecology would inform sustainable waste management. In the Balearic Archipelago of Spain, closure of an open-air landfill site provided an experimental setting to measure the effect of removing anthropogenic food on the average body mass, breeding parameters and body condition of opportunistic Yellow-legged Gulls Larus michahellis. After landfill closure there was a significant decline in the average body mass of breeding females and males (-10.4 and -7.8%, respectively), in average egg volume (-4.8%), and a shift in the modal clutch size from three to two eggs. Body condition decreased after landfill closure in both sexes. In breeding females, the drop in body weight was greater for birds with a low body size index. The differential response to a reduction of anthropogenic food between small and large birds suggests that food of anthropogenic origin contributes to tempering the effects of natural selection, making the long-term demographic effects of changes in food supply difficult to predict.

Original languageEnglish
Pages (from-to)439-448
Number of pages10
Issue number3
Early online date4 Apr 2015
Publication statusPublished - Jul 2015



  • Larus michahellis
  • Body condition
  • Egg volume
  • Experimental food reduction
  • Individual heterogeneity

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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