Affiliation: | aBritish Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK bJoint Nature Conservation Committee, Monkstone House, City Road, Peterborough PE1 1JY, UK cThe Wildfowl & Wetlands Trust, Slimbridge, Gloucestershire GL2 7BT, UK dRoyal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, UK eSOVON Vogelonderzoek Nederland/Dutch Centre for Field Ornithology, Rijksstraatweg 178, 6573 DG Beek-Ubbergen, The Netherlands fDepartment of Animal Ecology & Ecophysiology, Radboud University Nijmegen, Institute for Wetland and Water Research, P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands gDepartment of Environmental Science, Radboud University Nijmegen, Institute for Wetland and Water Research, P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands |