Among-colony variation in plastic ingestion by Yellow-legged gulls (Larus michahellis) across the western Mediterranean basin

The Mediterranean region is both a hotspot for biodiversity and for the accumulation of plastic pollution. Many species are exposed to this pollution while feeding, including a wide diversity of seabirds. Our objective was to investigate spatial variation in the quantity and types of plastic ingested by Yellow-legged gulls using information obtained from regurgitated pellets collected in 11 colonies. Anthropogenic debris, and particularly plastic, was found in pellets from all colonies, but the amount varied considerably. This among-colony difference was stable over the two years of study. The presence of marine prey and the proportion of agricultural area around the colonies significantly influenced the number of ingested plastics. As landfills close and garbage management improves, the availability of anthropogenic waste should decline. Following the response of gulls to these changes will be particularly useful for monitoring plastic pollution and for understanding the response of opportunistic wildlife to environmental modifications.