Mink are "decimating" colonies of sea birds on the Western Isles, RSPB Scotland have warned.
Mink are blamed for preying on other wildlife such as water voles
The mammals, a non-native predator on the islands, have been preying on nesting terns on Lewis.
The RSPB said five or six chicks are surviving when normally there should be more than 100.
Efforts to eradicate mink on Uist appear to be working and the RSPB hope a similar programme can be introduced to other parts of the Western Isles.
The society's Martin Scott said one tern colony in particular has been hit hard by mink attacks.
He said: "They've spread all the way across Lewis and have run amok through the tern colonies.
"This particular tern colony here at Gress just to the north of Stornoway has been decimated over the years very, very badly.
"I've found large numbers of dead adults, dead chicks and eggs and out of 200 pairs in recent years we have only been getting five to six chicks.
"You would be expecting well over 100 chicks to be surviving."
Mr Scott said controlling mink would reverse the trend of falling sea bird numbers.
He said: "We have seen in Uist with the removal of mink that birds are bouncing back and increasing and we hope very much the same will happen on Lewis."
It is believed they were brought from the US to be bred for the fur trade but were released or escaped from mink farms which were no longer commercially viable.