The origins, moult, movements and changes in numbers of Bar-tailed Godwits Limosa lapponica on the Wash, England

With an average peak of approximately 12 000 birds between 1987 and 1991 the Wash is the most important British estuary for Bar-tailed Godwits, holding 10% of the fetal European population. This paper describes the biometrics, wing moult and movements of approximately 3500 Bar-tailed Godwits caught on the Wash between 1960 and 1990 and relates this to the BTO's Birds of Estuaries Enquiry (BoEE) counts and other published information. Numbers of Bar-tailed Godwits counted on the Wash increased through the period 1970-90, increases being most apparent in the times of peak passage in October and February. In recent years approximately 8000 birds have moulted on the Wash, second-year birds starting in the first week in June and adults in the third week of July. The population takes 100-120 days to complete primary moult. Analysis of biometrics suggests that the majority of the moulting population on the Wash comes from breeding populations in northern Europe and Scandinavia, although small numbers of non-moulting birds, breeding further east, pass through in late August and early September. The data collected by the Wash Wader Ringing Group and the BoEE show that the Wash is one of the most important areas in Britain and Europe for the Scandinavian and west European breeding populations.