The Seasonally Divided Flight Feather Moult in the Barred Warbler Sylvia nisoria: A New Moult Pattern for European Passerines

Abstract

Wing and tail feather moult in Barred Warblers was studied during three summers in SE Sweden. Birds arriving at their breeding grounds had on average 3.2-4.9 fresh secondaries and 3.9-9.4 fresh tail feathers, most certainly moulted in winter quarters. A few primaries and tertials had also been renewed. After breeding, normally all primaries and tertials were moulted. Primary moult duration was approximately 40 d for the individual and 60 d for the population. On average, only 0.7-1.4 secondaries were shed. No individuals renewed any winter-grown secondaries the following summer. Normally, 3-4 (mainly central) tail feathers were moulted. Thus, Barred Warblers moult primaries, tertials and central tail feathers in summer, and secondaries and a varying number of tertials and tail feathers in winter. The juvenile winter moult of secondaries shows that the seasonally divided flight feather moult is actively initiated already in the first winter; this is interpreted as a preparation for an early departure from breeding grounds the following summer. This moult pattern has not previously been documented in European passerines.