Movement patterns of European Reed Warblers Acrocephalus scirpaceus and Sedge Warblers A-schoenobaenus before and during autumn migration

The foraging movements of European Reed Warblers Acrocephalus scirpaceus and Sedge Warblers Acrocephalus schoenobaenus at migratory stopover sites were studied by comparing the frequency distribution of distances between capture-recapture localities of individual birds with a simulation model of a random distribution of movements. The results indicate that Reed Warblers have no defined home ranges before autumn migration, but move randomly or nearly randomly between localities at a stopover site. Reed Warblers and Sedge Warblers at migratory stopovers have home ranges that are too large to be exclusive territories. Previous studies have shown that Robins Erithacus rubecula and Wrens Troglodytes troglodytes have well-defined small home ranges at stopovers. It is suggested that the reason for these differences is due to the differences in feeding ecology of the species concerned, in particular the spatial distribution of their prey. Both Reed and Sedge Warblers forage on invertebrates, which are unpredictable in their distribution and in the timing of their occurrence.