Conservationists have conceded defeat in their efforts to protect populations of capercaillie in the Trossachs and Argyll.
They said there were now only a few birds left and little or no breeding was taking place.
The Cairngorms are the traditional stronghold for Scotland's capercaillie population, but the birds can still be seen further south.
Scottish Natural Heritage said these southern populations had dwindled.
The few birds that are left are centred on the islands in Loch Lomond.
“We have seen no signs of breeding activity in the last two years,” Alan BellNatural heritage manager
SNH, the Loch Lomond and the Trossachs National Park Authority, RSPB Scotland and local landowners have all worked together to halt the decline, but without success.
Wet summers, predation, loss of habitat, collisions with deer fences and human disturbance are all thought to have played a part in the decline of the species.
Alan McDonnell of SNH said: "The capercaillie is a highly valued part of Scotland's nature, culture and history and we are committed to ensuring its long term survival.
"A lot of people and organisations have worked for many years to help the population of capercaillie on the Loch Lomond islands, but we need to face the facts about this increasingly isolated group of birds.