Disentangling the influence of taxa, behaviour and debris ingestion on seabird mortality

Marine debris is a growing threat to hundreds of marine animal species. To understand theconsequences of marine debris to wildlife populations, studies must go beyond reporting theincidence of wildlife and debris interactions and aim to quantify the harm resulting from theseinteractions. Tubenosed seabirds are globally threatened, with a near universal risk of debrisingestion and an unquantified risk of mortality due to eating plastics. In this paper, we explore themortality risk narrative due to the acute effects of debris ingestion, and quantify behavioural andecological factors including age, diet and foraging method. We examined ingested debris loads,types and mortality of 972 adult and immature seabirds across 17 albatross, shearwater and prionspecies in a global seabird biodiversity hotspot. Though age and foraging method interact toinfluence the incidence and number of items ingested, age and diet were the most importantfactors influencing mortality. Mortality is influenced by debris load and type of debris ingested andthere is selectivity for items that visually resemble a seabird’s prey. Immature birds that forage oncephalopods are more likely to ingest and die from eating debris than are adults. Conversely, therisk of death to seabirds that forage on crustaceans is linked to the number of plastic items ingestedand is higher in adults. Debris ingestion is an under-recognised cause of tubenose mortality and islikely negatively affecting rare and threatened species