Researchers from the Doñana Biological Station assessed the spatial variation in concentrations of ten metals in faeces of the lesser black-backed gull (Larus fuscus) wintering at seven localities in South-West Spain. They found high concentrations of metals in gull faeces, with several elements (arsenic, copper, molybdenum, lead and zinc) locally exceeding (by 2 to 11 times) derived Lowest Effect Level (LEL) values.