Rats will be removed from the Isles of Scilly because of the threat they pose to native wildlife.
The charity Royal Society for the Protection of Birds (RSPB) said the rodents have been found on one of the islands and are now threatening local wildlife and sometimes unique and rare seabirds.
Jacqueline Pearson, biosecurity officer for the RSPB, said they were spotted on St Agnes and Gugh in 2013, but were removed as they can endanger nesting birds.
The RSPB said the rats “are very good swimmers” and believe they swam back over from the surrounding islands.
The charity said it does not know how many rats are occupying the islands but insisted the animals pose a threat to seabirds as their eggs are an alternative food source for the rodents.
Ms Pearson told the BBC: “A number of rats have been spotted on the uninhabited Round Island during a survey last week.
“We are working hard to get rid of them before the birds return from South America for breeding season.”
The conservationist added: “We’ve all rallied together because unfortunately we have found rats on round island and that means they will predate our special seabirds.”
Manx shearwaters and storm petrels are among the birds due to return to the Isles of Scilly for breeding season in March.
A group of volunteers have now set up bait stations on Round Island in a bid to limit any harm caused by rats.
Ms Pearson added: “We’ve got all our permissions to put out bait stations, they should be attracted to it and by putting it in 50 metre territories we should be able to remove every rat before the breeding season begins.”