1. Department of Biology; University of York; Wentworth Way; York; YO10 5DD; UK
2. Department of Biosciences; University of Helsinki; P.O. Box 65 (Viikinkaari 1); FI-00014; Finland
3. Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, University of Southampton, Highfield Campus; Building 85; Southampton; SO17 1BJ; UK
4. Centre of Terrestrial Carbon Dynamics (York Centre), Stockholm Environment Institute at York & Environment Department, University of York; York; YO10 5DD; UK
5. Department of Meteorology; University of Reading; Reading; RG6 6BB; UK
6. NERC Centre for Ecology and Hydrology; Wallingford; Oxfordshire; OX10 8BB; UK
7. British Trust for Ornithology, The Nunnery; Thetford; Norfolk; IP24 2PU; UK
8. Department of Ecology and Evolutionary Biology; University of Tennessee; 569 Dabney Hall; Knoxville; TN 37996-1610; USA
9. Environment and Sustainability Institute, University of Exeter; Penryn; Cornwall; TR10 9EZ; UK