CONSERVATIONISTS last night sounded a warning about the future of the curlew - once one of North Wales's most popular upland birds. It came after the biggest ever headcount revealed a big fall in numbers in only three years. A North Wales survey, part of a UK-wide operation, showed an 82% decrease since 2002. And last night the Royal Society for the Protection of Birds said more research into potential causes including climate change, acid rain and the loss of moorland heather was expected to be revealed later this year by the British Trust for Ornithology. But other birds are enjoying a Welsh revival. The stonechat, a relative of the robin, enjoyed a 10-fold increase while raven numbers almost quadrupled. | 
