Marginal presence of plastic in nests of yellow–legged gulls (Larus michahellis) in the southeastern Bay of Biscay

Marginal presence of plastic in nests of yellow–legged gulls (Larus michahellis) in the southeastern Bay of Biscay. Nest entanglement and consumption of plastics can be a cause of mortality in chicks of various seabird species. As plastic debris may be chosen as a source of nesting material, evaluation of its presence and contribution to nest building in seabird colonies is important. Here, we determined the contribution of anthropogenic debris to nest construction by a yellow–legged gull Larus michahellis population that largely depends on refuse tips to forage. Two colonies within the southeastern Bay of Biscay, Spain, were sampled in 2019. One of the colonies was in Getaria, where no debris was found in nests, and the second was in Ulia, where 40 % of the nests had some kind of artificial material. In all cases, however, this debris comprised less than 5 % of the nests' area. Among the studied nests, we found one had a piece of fabric, five had pieces of rope, and 20 had pieces of flexible plastic packaging. These results contrast with other seabird species that face problems of conservation due to the increasing use of plastic for nesting. With the low prevalence of artificial debris (chiefly plastic) in nests found in this study, mortality due to debris entanglement or ingestion is unlikely.