Postbreeding migration of the Sedge Warbler Acrocephalus schoenobaenus in the Czech Republic

Abstract

In 1979-1990, postbreeding migration of the Sedge Warbler Acrocephalus schoenobaenus was monitored at two sites in the northeastern part of the Czech Republic. The study area was used by a local population, and populations from southern Finland and the eastern Baltic, which then continued in their flight to suitable sites in Austria, Hungary and Slovenia. A total of 8456 Sedge Warblers were captured, of which 17% were retraps. The number of birds captured over a comparable period (15/7-28/8) in different years varied considerably, and at one of the sites, the minimum was 6.6 times smaller than the maximum. Differences were also found between the two sites. Migration of adult and juvenile Sedge Warblers peaked during the second half of July and the first or second ten day period of August, respectively . At the site where fat accumulation measurements were taken during different years, moderate increases were not observed before Day 4.