Wing moult of Eastern Olivaceous Warblers Hippolais pallida reiseri at stopover sites at the southern fringe of the Sahara

Recent research on the systematics of the genus Hippolais led to the proposal to split Olivaceous Warbler Hippolais pallida into Western Olivaceous Warbler H opaca and Eastern Olivaceous Warbler H pallida with the subspecies pallida, elaeica, laeneni and reiseri. Here, we present data on postnuptial primary moult in relation to age, for H p reiseri from five sites in southern and central Mauritania in late summer and autumn, 2003. Adult birds showed either interrupted primary moult or had not yet started to moult their primaries. First year birds were either not moulting in September or were actively moulting primaries in October. We suggest that some adult birds start primary moult on the breeding grounds and interrupt moult for migration. On the wintering grounds, adult birds either resume interrupted primary moult or moult their primaries completely. First year birds do not start primary moult on the breeding grounds but moult their primaries completely on stopover sites at the southern fringe of the Sahara prior to further southward migration. We discuss possible problems with this hypothesis and conclude that further research is needed to verify some of its assumptions.

Volker Salewski, Marc Herremans and Thomas Stalling, Ringing & Migration (2005) 22, 185-189