The GSPCA said Percival was one of the few survivors of a “worrying and widespread incident affecting coastal wildlife”.
It said similar events in the past were caused by “severe storms and environmental disturbance”.
“Rough weather exhausts many species of seabirds and makes feeding incredibly difficult,” it said.
“When this oil coats a bird’s feathers, it destroys their waterproofing, leaving them cold, unable to fly or float, and in danger of poisoning as they try to clean the toxic substance from their plumage.”