The use of plastic debris as nesting material by a colonial seabird and associated entanglement mortality

► Plastic entanglement causes mortality but the population-level consequences are unknown. ► At one colony, northern gannets used 18.46 tonnes of plastic for nesting material. ► Synthetic rope appears to be preferentially selected. ► On average 65.63 birds are entangled annually. ► Current levels of mortality are unlikely to have population-level effects.