Abstract
Marine debris is a growing threat to hundreds of marine animal species. To understand the consequences of marine debris to wildlife populations, studies must go beyond reporting the incidence of wildlife and debris interactions and aim to quantify the harm resulting from these interactions. Tubenosed seabirds are globally threatened, with a near universal risk of debris ingestion and an unquantified risk of mortality due to eating plastics. In this paper, we explore the mortality risk narrative due to the acute effects of debris ingestion, and quantify behavioural and ecological 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 prion species in a global seabird biodiversity hotspot. Though age and foraging method interact to influence the incidence and number of items ingested, age and diet were the most important factors influencing mortality. Mortality is influenced by debris load and type of debris ingested and there is selectivity for items that visually resemble a seabird’s prey. Immature birds that forage on cephalopods are more likely to ingest and die from eating debris than are adults. Conversely, the risk of death to seabirds that forage on crustaceans is linked to the number of plastic items ingested and is higher in adults. Debris ingestion is an under-recognised cause of tubenose mortality and is likely negatively affecting rare and threatened species.
Highlights
Pollution of the marine environment by plastics and other anthropogenic ‘marine debris’ is a global problem for marine life, with more than 1400 species known to interact with marine debris [1]
We examined marine debris ingestion in 972 seabirds to explore the differences among three tubenose groups, albatrosses (N = 243; ad = 222, imm = 21), shearwaters (N = 391; ad = 327, imm = 64) and prions (N = 338; ad = 106, imm = 232)
Age and diet are important factors for determining the risk of mortality resulting from marine debris ingestion to seabirds, but the influence of age on risk is not consistent between species
Summary
Pollution of the marine environment by plastics and other anthropogenic ‘marine debris’ is a global problem for marine life, with more than 1400 species known to interact with marine debris [1]. There is particular concern for the potential impact of marine debris on seabirds due to the number of seabird species that are threatened or in decline [2], and their increasingly high frequency of reported debris ingestion [3, 4]. The conversation about marine debris ingestion is evolving from reporting species-specific debris ingestion rates to analysis of risk of harm and mortality in order to quantify population effects and the ecological consequences of debris ingestion [5, 6]. Disentangling which species’ populations are threatened by debris ingestion begins with identifying the behavioural and ecological factors that may put some species at higher risk than others. Does more debris ingestion directly translate to more death, or do behavioural and ecological factors influence the risk of mortality?
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