Winterquartier und Mauser der Dorngrasmücke,Sylvia communis

Abstract

Moult and Winterquarters of Sylvia communis Examination of about 170 skins ofSylvia communis, in the majority collected in African winter quarters, led to the following conclusions: 1.) Adults of European populations undergo a complete postnuptial moult in July/August before migrating to Africa, while the Asiatic populations have a complete moult in winter quarters, usually starting in January or February and ending in late February or in March. Young birds hatched in Europe renew the flight feathers for the first time when about 12 months old, thus at the same time as the adults. On the other hand, young birds of Asiatic origin moult the flight feathers in first winter (usually in Jan./Febr.) at the age of 6 months. 2.) The seasonal difference of complete moult proves to be a reliable criterion for determining the winter quarters of European and Asiatic Common Whitethroats. a) European populations(S. c. communis) — Winter quarters confined to African countries north of the equator. b) Asiatic populations (S. c. icterops and“volgensis“) — Winter quarters mainly south of the equator, as far south as Nyasaland and Rhodesia (a few even reaching Transvaal and Damaraland). The winter quarters of both groups overlap in Ethiopia, Kenya, Uganda and in the surroundings of Lake Albert. 3.) A partial moult, confined to body, tertials, and sometimes central tail feathers, takes place in the European populations about Jan./Febr., in the Asiatic populations about July. 4.) A comparable case of population difference in season of moult is offered by the Ringed Plover,Charadrius hiaticula. The southern (for instance the British) populations of that species have a complete moult July to September. The Arctic populations moult the flight feathers in Winter (November to March), after reaching Southern Africa, the “goal“ of their long migration route (seeStresemann 1966).