Plastic ingestion in adult and fledgling Manx Shearwaters Puffinus puffinus on Skomer Island, Wales

Plastic debris is ubiquitous in the marine environment, and seabirds are among the most impacted marine vertebrates. Plastic ingestion was investigated in an internationally-important breeding population of Manx Shearwaters Puffinus puffinus on Skomer Island, Wales in 2018–19. Opportunistic necropsies were carried out on a total of 34 birds to collect contents of the gastrointestinal tract: 13 adults in April – July 2018 and 12 fledglings during September 2019, and a further nine opportunistic necropsies carried out from adults in July – September 2018. The presence, quantity, size and colour of plastic in the gastrointestinal tract was investigated. Plastic was found in 71% of stomach contents (68% of adults, 75% of fledglings). Adults were found to have larger plastic pieces in their gastrointestinal tract than fledglings, and lighter birds had larger pieces of plastic in their tracts than heavier birds. This study shows that Manx Shearwaters on Skomer Island are vulnerable to plastic ingestion, and that adults are likely to pass plastic to their chicks