Ogilvie, M. A. and Cook, W. A. (1971) “Differential migration of the sexes and other aspects of the recovery overseas of mallard ringed at Borough Fen Decoy, Northamptonshire”, Wildfowl, 22, pp. 89–97. Available at: https://tidsskrift.dk/Wildfowl/article/view/155410 (Accessed: 5 April 2026).