Plastic biovectoring by two closely-related gull species to coastal marshes

Plastic pollution is a global threat to biodiversity. While physical factors are well known, the role of animals in the spread of plastic is less understood. Here, we compared the role of two closely related gull species with different migratory behaviour, dispersive patterns and habitat use-the yellow-legged gull (Larus michahellis) and the lesser black-backed gull (Larus fuscus)- as biovectors of plastics to a coastal Ramsar site in southwestern Spain. We quantified and characterized plastic present in pellets of both species. We combined pellet analyses with individual movements tracked by GPS and census data to estimate the amount plastic imported, in terms of mass and number of items. In total, 89.9% of pellets contained plastics, mostly as microplastics (