Plymouth experts have identified the waxy substance which has coated and killed hundreds of seabirds on the Devon, Dorset and Cornwall coast.
The substance has been found on dead and living birds along the coast and causes burning to the skin.
Experts at Plymouth University say it is a type of polyisobutene, an additive in lubricating oils.
The information, gathered from examination of the congealed feathers of a guillemot, is being passed on to the Maritime and Coastguard Agency and the RSPCA.
Plymouth chemical analyst Professor Steve Rowland told the BBC: "It's very sticky and semi-solid, hence its acting on birds' feathers like a glue.
He added: "Residues will probably stay around in the environment for some time, though hopefully not in this large mass that pollutes the birds."
More than 300 birds have washed up with polyisobutene on their feathers - as well as burning it causes their feathers to lose waterproofing and heat retention properties.