NIGHT MOVEMENTS OF YOUNG REED WARBLERS (ACROCEPHALUS SCIRPACEUS) IN SUMMER: IS IT POSTFLEDGING DISPERSAL?

Abstract

I studied summer movements of juvenile Reed Warblers (Acrocephalus scirpaceus) marked as nestlings during four fi eld seasons (1999–2002). To control for birds‘ movements, nocturnal playback of songs and daytime mist-ne ing were done. Captures by song playback suggest the existence of nocturnal postfl edging movements in Reed Warblers. Birds’ age (days) during such movements was found to be 39–52 days. I analyze the temporal schedule and physiological condition of the birds during this period and discuss the mechanism of nocturnal postfl edging dispersal and its background and relationships with other events of the annual cycle during the premigratory period.