WALTERS J (1987) Primary moult in the Curlew Numenius arquata on an inland roost. LIMOSA 60 (1): 9-12.

On 36 days, spread over the period 1 July-20 September 1983, 1220 shed primaries of the Curlew were collected on a roost near Amsterdam. These primaries were classified according to length (P1-P7 and most P8) and the maximum breadth of the outer flag (some P8 and all P9 and PlO). The reference series for the lengths consists of 14 sets of primary lengths of known order from Curlews found dead (app. 1). Since there is an overlap in lengths between adjacent primaries, individual primaries cannot be separated with certainty when compared with the reference series, but large numbers can be separated statistically. For that purpose the length where the probability of a primary noted as PX being a short PX+1 is equal to the probability of a primary being noted as PX+1 being a long PX, is calculated from the reference series and is the basis for the statistical lower and upper limits of the primary lengths in appendix 1. The maximum breadth of the outer flags of 20 PlO is 1.8-3.0 mm and that of 20 P9 3.9-4.9 mm (collection ITZ, Amsterdam). The numbers of shed primaries collected, so classified, are given in appendix 2. The unit for the progress of active primary moult, the average primary per date, is calculated from appendix 2 and the results are plotted in figure 1. Data from Sach (1968) for Mellum, treated in the same way, are also shown in figure 1 and appear to be in close agreement with the progress in the entirely different ecological conditions of the Amsterdam area. An average primary of 10 is reached by the end of September, so that the primary moult could be completed by mid November, including c. 50 days of growth of PlO according to Sach (1968). The primary moult in the Black-tailed Godwit Limosa limosa (van Dijk 1980), for this study also expressed in average primary per date, is about two weeks in advance of the Curlew, though nowadays both species breed equally early. The Oystercatcher Haematopus ostralegus (partially after Hulscher 1977, partially own observations near Amsterdam) moults c. 1V2 months later than the Curlew, though the difference in the breeding period is only c. three weeks and both species are not under time pressure of an early and far migration as in the Black-tailed Godwit. Curlew Numenius arquata

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