Affiliation: | British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK; WildWings Bird Management, 2 North View Cottages, Grayswood Common, Haslemere, Surrey GU27 2DN, UK; Beck Cottage, The Green, Atwick, Yorkshire YO25 8DQ, UK; Northumbrian Water, Abbey Road, Pity Me, Durham DH1 5FJ, UK |