Effects of culling yellow-legged gulls Larus cachinnans on three species of heron nesting within a large gull colony on the Medes Islands, Cataluña, Spain

  • Published source details Bosch M. (1996) The effects of culling on attacks by yellow-legged gulls (Larus cachinnans) upon three species of herons. Colonial Waterbirds, 19, 248-252


This study is summarised as evidence for the following.

Action Category

Reduce inter-specific competition for food by removing or controlling competitor species

Action Link
Bird Conservation
  1. Reduce inter-specific competition for food by removing or controlling competitor species

    A before-and-after study from 1993-1995 at a heronry on an island off north-east Spain (Bosch 1996) found that there was no difference in kleptoparastic attacks by yellow-legged gulls Larus cachinnans on either little egrets Egretta garzetta or night herons Nycticorax nycticorax following the culling of gulls herons (0.30 attacks/hour before the cull, 54 hours, 1081 heron flights and 16 attacks recorded; 0.32 attacks/hour after the cull, 98 hours and 3581 heron flights and 13 attacks recorded). The gull population declined from approximately 13,500 pairs in 1993 to approximately 7,500 pairs in early April 1995, following the poisoning of breeding adults every year starting in 1992. All attacks were on herons in flight by subadult gulls (which would not be affected by the culling) and unsuccessful attacks were recorded.


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