Guanay cormorant (Leucocarbo bougainvilliorum) pellets as an indicator of marine plastic pollution along the Peruvian coast.

Plastic pollution affects many taxa worldwide, and monitoring is crucial for understanding its impacts, particularly where plastic reaches threatened species or those destined for human consumption. This study evaluates plastic ingestion in Near Threatened guanay cormorants (Leucocarbo bougainvilliorum), which catch prey that are also targeted by fisheries, through pellet analysis at ten locations in Peru. Plastic occurred in 162 (7.08 %) of 2286 pellets, consisting of mainly user plastics, including 5 % between mega or macro (>20 mm), 23 % meso (5-20 mm), 67 % micro (1-5 mm) plastics and 5 % ultrafine (1 μm-1 mm). We found significantly higher percentages occurrence of plastic for colonies close to more river mouths. Our results show that seabird pellet sampling is a useful tool for monitoring marine plastic pollution in Peru.