Duration and a shift in timing of primary moult of Eurasian Curlews Numenius arquata arquata in northern Scotland

Eurasian Curlews Numenius arquata arquata which moult and winter in the Moray Firth, northern Scotland, had a mean start date of 24 June (95% range 18 May to 31 July) for primary moult, which then took a mean of 122 days, giving a mean completion date of 24 October (95% range 17 September to 30 November). The duration is within the pattern of longer moult duration in larger waders that spend the winter in the northern hemisphere. There was no difference in timing and duration of moult between males and females. The gap in the wing surface area created by the loss of primary feathers reduced slightly during moult. A comparison of moult data collected between the years 1978–2000 and 2001–2023 showed that Curlews moulted three days earlier in the latter period. This shift in the timing of moult could be a consequence of earlier breeding and migration in response to climate change, or an increase in breeding failure, as indicated by the reduced recruitment of first-year birds in the Moray Firth.