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ABSTRACTThis study aims to determine the level of movement of individuals between the Icelandic and Northwest Mainland European (NWME) Whooper Swan Cygnus cygnuspopulations, and to assess the extent to which this interchange affects total population estimates. Ringing, resighting and recovery data for Whooper Swans ringed across Europe since the early 1900s were compiled from the EURING Data Bank, national ringing schemes and individual ringers. Birds were assigned to the biogeographical population (Icelandic or NWME) in which they were ringed. Of >18 000 Whooper Swans ringed in 17 European countries, 172 individuals (0.94%) were later found outside the nominal range of their assigned biogeographical population. The proportion of ringed swans from the Icelandic population that were subsequently found ‘out of range’ did not differ significantly from the proportion recorded for the NWME population, indicating no directional bias in population interchange. Population switching by Whooper Swans in western Europe occurs consistently, but currently at very low levels. Our results reinforce the view that such levels of population interchange are unlikely to have caused major inaccuracies or biases in the total numbers recorded during the coordinated censuses used to estimate population size.

ABSTRACTAnalyses of 2280 re-encounters made during 2014–20 of 300 adult British Greylag Geese Anser ansermarked at Windermere, Cumbria, in summers 2013–16 are used to describe the patterns of their moult migration. Results show that birds moulting at Windermere are migrating mainly from the nearby counties of Lancashire, North Yorkshire and West Yorkshire, and from within Cumbria itself. Resightings at Windermere showed that the number of individuals returning to moult decreased during the study: possible reasons for this are given. We also provide new and updated information on the survival and mean dispersal distance for non-breeding British Greylag Geese. The mean dispersal distance away from Windermere for all marked individuals was 83.3 km (95% CI  73.4–93.2). Annual mean survival rates ranged between 0.568 and 0.872 over the study period, with a mean of 0.680 (95% CI  0.584–0.775). Results from this study contribute to improving our knowledge of the demography of the British Greylag Goose population.