1. Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
2. School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
3. Biomathmatics and Statistics Scotland, Craigiebuckler, Aberdeen AB15 8QH, UK
4. Royal Society for the Protection of Birds Scotland, Etive House, Beechwood Park, Inverness IV23BW, UK