Some results of recent British Mallard ringing

Abstract

Between 1939 and 1949 very few Mallard were ringed in Britain. Almost all those ringed since 1949 have been caught at Abberton Reservoir, Essex (about 1600 birds), where intensive trapping is carried on by Maj-Gen C. B. Wainwright, or at Berkeley New Decoy, Slimbridge (about 2000 birds). Captures of ducks at these places and their recoveries there or elsewhere, with some references to earlier ringing, are used to answer three questions and illustrate some of the problems involved in making valid inferences about the distribution and mortality of the species from recoveries of marked birds. The questions considered are: (1) Is the mortality of British Mallards in their first winter higher than that of older birds? (2) Why is the proportion of males recovered higher than that of females? (3) What is the significance of variations in the sex-ratio amongst ducks caught at different times of the year?.