Length of stopover, fuel storage and a sex-bias in the occurrence of two subspecies of Red Knots Calidris c. canutus an d C.c. islandica in the Dutch Wadden Sea during southward migration.

During southward migration the Wadden Sea is the meeting place of Red Knots Calidris canutus of two subspecies that breed in either western Siberia (C. c. canutus) or north Greenland and north-east Can ada (C. c . islandica), but the details of their co-occurrence have not been described. In 1995- 98 numbers of Red Knots in our study area in the western Dutch Wadden Sea usually built up in late July towards maxima of 10.000-20.000 individuals in August and early September. In each of these four years we attached tiny ( 1 .3-1 .8 g) radiotransmitters to a total of 95 molecularly sexed adults to determine the length of stay of different categori es of birds.

Nebel, S ., T. Piersma, J . van Gils, A. Dekinga & B . Spaans 2000, Ardea 88(2) : 165-176