Spring migration of the Siberian Knots Calidris canutus canutus: Results of a co-operative Wader Study Group project

In spring 1979 the Wader Study Group organised a co-operative project to study the spring migration of Siberian Knots Calidris c. canutus from their west and south African wintering grounds to the breeding grounds in central Siberia. S. African wintering birds migrate via the western seaboards of Africa and Europe. Siberian Knots seem to use only a few staging sites between W. Africa and Siberia. Most birds only use the W. German Wadden Sea. Staging areas of lesser importance are the Tejo Estuary in Portugal, the Vendée coast in France and, probably, the Westerschelde in SW Netherlands. At the latter three sites in early May, birds appear to arrive with lower body weights than in Schleswig-Holstein (W. Germany) at the same time. The migration from W. Germany to central Siberia is most probably made in one flight via the Gulf of Finland. Detailed information on the timing of migration is presented. A model on body weight changes during migration in a fixed time schedule is employed to discuss the energetic constraints on the migration strategy of Siberian Knots.