1. Rothamsted Research; West Common Harpenden Hertfordshire AL5 2JQ UK
2. INRA, UMR 1347 Agroécologie, Pôle ECOLDUR; 17 rue Sully Dijon CEDEX 21065 France
3. 168 Putteridge Road Luton LU2 8HJ UK
4. Game and Wildlife Conservation Trust; Burgate Manor Fordingbridge Hampshire SP6 1EF UK