RENEERKENS J, J LOONSTRA, B SPAANS & T PIERSMA (2012) Large numbers of Sanderlings Calidris alba from all directions near griend in the Dutch Wadden Sea in late summer of 2011. LIMOSA 85 (2): 73-79.

In August and September 2011 we observed a very large number of Sanderlings on the mudflats close to the island of Griend in the central Dutch Wadden Sea. Colour-ring resightings of birds that were ringed in the Wadden Sea or abroad and/or were later re-sighted elsewhere showed that the Wadden Sea is visited by Sanderlings that winter anywhere along the Western European and West-African coast south of the Wadden Sea, from The Netherlands south to at least Namibia. These Sanderlings breed in Greenland. Whether Western Europe is also frequented by Sanderlings from the Siberian breeding populations remains a matter of debate. Based on a few counts, as well as the proportion of colourringed individuals in flocks and the total number of different individuals present in the area at the time, we estimate that in August 37,000 (95% confidence interval 13,200 - 61,800) and in September 11,200 (CI 4,500 - 17,900) Sanderlings used the central western Dutch Wadden Sea during the southward migration season of 2011. The presence of 16% juveniles in September which were not observed in August suggests a fair amount of turnover. This suggests that a third of the presently estimated total population size may stop over in the Wadden Sea, but we take this conclusion with a grain of salt and suggest that both the total population size estimate and the estimate of the number of Sanderlings in the Wadden Sea need reassessment.

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