Importation of plastic fragments into a seabird colony: accident or design, threat or benign?

Abstract

Summary Plastic pollution affects marine ecosystems worldwide and poses risks for seabirds. Most recorded impacts on organisms are negative but, in some cases, the constructive use of plastic fragments or objects by birds has also been recorded. Small blue and green plastic fragments are found scattered among nests in a large (c.500,000 pairs) Sooty Tern Onychoprion fuscatus nesting colony on Bird Island, Seychelles. We investigated whether the fragments were being imported by the birds, and if so whether import was accidental or intentional. We found that Sooty Terns were the only seabird species to have plastic fragments in their nesting area and import of fragments varied seasonally and spatially. Throughout the colony, plastic fragments were imported during egg-laying, incubation, and chick-rearing, but import declined as chicks began to fledge. A part of the colony where all eggs were harvested for human consumption received more fragments than among undisturbed nests. We failed to find evidence of ingestion and excretion of fragments and suggest other avenues for investigation.