Local use of landfills by a yellow-legged gull population suggests distance-dependent resource exploitation

Egunez, Alexandra; Zorrozua, Nere; Aldalur, Asier; Herrero, Alfredo; Arizaga, Juan

27 November 2017

Understanding the use of feeding sources at the local scale is crucial in comprehending the factors driving population dynamics, dispersal and territory use. Many gull (Larus spp.) populations have increased sharply, which is partly promoted by their use of landfills as a food resource. Although at the large scale it is known that birds from mainland colonies feed more on landfills than those from offshore colonies, at the local scale, this distance-dependent exploitation has been little studied. Here, then, we study whether the extent of gulls’ use of landfill is distance-dependent through the study of 3 different gull colonies and five separate landfill sites within a relatively small geographical area. After controlling for bird numbers by both age cohort and colony, we observed that the number of gulls found at each landfill was colony dependent and that it decreased non-linearly with increased distance to place of birth.