BOERE GC, BRUIJNE, JWA, DE & NIEBOER, E (1973) A study on the significance of the Dutch Waddensea-area for the Dunlin Calidris alpina in late summer and autumn. LIMOSA 46 (3): 205-227.

Dunlin Calidris alpina = Calidris alpina schinzii Dunlins Calidris alpina were caught with mistnets in 1970 at Schiermonnikoog, Vlieland (islands. of the Dutch Wadden Sea) and for comparison, in Southern Flevoland in the second half of August, the end of September and the first half of October, respectively. During the passing of the season we caught, in relation to the number of adults, increasing numbers of juveniles (Table 1). This shift is most probably caused by the gradual replacement of the adults by the juveniles. At Schiermonnikoog there was in the adults a clear correlation between length of bill and weight (Fig. 2). At Vlieland this correlation was absent and many birds caught were relatively heavy (Fig. 3). All of these latter birds had new primaries. It is most likely that this category had already finished primary-moult for some time and thus had had enough time to form fat-deposits to continue migration to its winter-quarters. Among the juveniles at Vlieland we found relatively light, as well as relatively heavy birds (Fig. 4). Presumably birds of the first group had just arrived and had a reduced weight following a long flight; the second group was probably already for some time in the area of the Wadden Sea and must have had there the opportunity to form fat- deposits. Just as in 1968 and 1969 (Nieboer 1972), most Dunlins belonged on account of their measurements to a northern race (Figs. 5 and 6). One specimen might belong to the southern subspecies C. alpina schinzii or else to the Greenland form C. alpina arctica. At the end of August the primary moult of the adults was in full swing; at the end of September it has, nearly finished (Fig. 7). Adult Dunlins of Schiermonnikoog, though caught in one night, were in very different phases of primary moult (Fig. 8). This may indicate the presence of different groups of adult Dunlins in the same period. At Schiermonnikoog, the adults most progressed in primary moult, had on the average a smaller bill than the others (Table 3). Moult of body-feathers in the adults came to an end after the end of th'e primary moult. In juveniles this moult apparently took place later in the season than in adults Crable 4). If juveniles use the Waddenseaarea as a winter-quarter, than they probably complete the replacement of their bodyfeathers at that place. Presumably the Waddensea-area acts as a moulting place for the autumnal moult of adult Dunlins. Important indications are: 1. Large numbers of moulting adult Dunlins are found there during a long time (August and September). 2. From the end of September till the beginning of October the numbers of adult Dunlins decrease sharply in the Wadden Sea. A. J. Prater). Possibly it concerns the same birds. In literature we find two opinions about the division into subspecies of C. alpina. Fig. 12 shows the opinion of Kozlova (1962) and Uspenski (1969). Fig. 10 represents that of a.o. Witherby (1952), VOOllS (1960), Vaurie (1%5), Salomonsen (1967) and Havtorn (1971). In our opinion, most arguments are in favour to the conception of Fig. 13. The two opinions mentioned, give rise to two different interpretations about the post-glacial history of distribution of the Dunlin; both interpretations are discussed in the appendix. In our opinion the interpretation derived from the subspeciesclassification of Fig. 13 is more supported by zoogeographical and geological data than that based on the classification of Fig. 12.

[free pdf] [dutch summary]