Capercaillie have been known to attack humans

That may be down to global warming as the cold in April and damp in June has affected the blaeberry - one of the capercaillie's favourite foods.

But forest fences put up to stop deer running wild have also been highlighted as a major problem.

The birds cannot see the fences and fly to their deaths.

The RSPB wants landowners and the government to look more carefully at deer management policies and the impact they have on the birds - in particular the erection of fences.

The EC has asked the executive to investigate new ways of preventing their extinction.

And George Kremilis of the EC Environment Directorate is seeking reassurance from the Scottish Natural Heritage that Special Protection Areas are not too small.

'Best efforts'

Wildlife consultant Robert Moss had complained to the EC, claiming the quality of six protection sites are not adequate.

He said the sites, which measure a few thousand hectares, need to be expanded tenfold.

A spokesman for SNH, which is responsible for the sites, said: "We are making our best efforts to protect endangered species in Scotland."

The birds have already died out in parts of Sutherland and West Perthshire.

The capercaillie is big enough to be nicknamed the "horse of the woods" and was hunted to extinction in the late 18th century.

It was re-established in 1837 when the Marquis of Dunblane brought 50 birds from Sweden, but now it is confined to central and north-east Scotland.

The males can be very aggressive and have been known to attack deer, dogs, sheep and even humans if they are disturbed.