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 an d Sedge Warblers Acrocephalus schoenobaenus at migratory stopover sites wer e studied by comparing the frequency distribution of distances between capt ure-recapture localities of individual birds with a simulation model of a r andom distribution of movements. The results indicate that Reed Warblers ha ve no defined home ranges before autumn migration, but move randomly or nea rly 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 ru becula and Wrens Troglodytes troglodytes have well-defined small home range s at stopovers. It is suggested that the reason for these differences is du e to the differences in feeding ecology of the species concerned, in partic ular the spatial distribution of their prey. Both Reed and Sedge Warblers f orage on invertebrates, which are unpredictable in their distribution and i n the timing of their occurrence.