Manx shearwaters travel from Welsh and Scottish islands to the South Atlantic, facing plastic ingestion, longline bycatch, and rat predation at nesting burrows.
Shearwater welfare is closely tied to the health of their island nesting sites and the open ocean. Rat predation causes severe distress and mortality at colonies, with eggs and chicks being taken overnight. Birds that ingest plastic suffer gut impaction and starvation. Bycatch victims experience drowning or severe hook injuries. Restoration of rat-free islands dramatically improves breeding success and individual welfare.