Rapid changes in vegetation structure of Aquatic Warbler habitats in Pomerania – outcomes of targeted five year habitat management
Tanneberger, Franziska; Knöfler, Vera; Linke, Wilhelm; Tegetmeyer, Cosima; Kloskowski, Janusz
Plant Diversity and Evolution Volume 130 No. 3-4 (2013), p. 303 - 313
published: Dec 1, 2013
The Aquatic Warbler is the rarest and only globally threatened passerine bird of mainland Europe and a specialist for sedge fen mires and similarly structured wetland habitats. Its Pomeranian population (NE-Germany/NW-Poland) is critically endangered. In this study, we analyse the effects of a targeted EU LIFE project on habitat suitability in Pomeranian breeding sites of the Aquatic Warbler and present recommendations for their further management, particularly in the largest site, Rozwarowo Marshes. Aquatic Warbler censuses and habitat assessments along transects were performed in 2006–2010. We focused our analysis on parameters that have been identified as crucial for Aquatic Warbler habitat selection in Pomerania in earlier studies: height of the litter layer, vegetation height, and cover of herbs. In the last year of the project (2010), out of 14 transects (with six suitable before the project) five transects can be regarded as suitable, and along five other transects habitat suitability had increased substantially. Winter mowing was not sufficient to maintain habitat suitability in one transect, probably subject to substantial eutrophication. At summer mown transects, vegetation height decreased strongly when mowing was implemented already in June/July. In nutrient-rich sites, vegetation height increased despite of summer mowing. Eutrophication should be immediately addressed as a major threat to Aquatic Warbler breeding sites in Pomerania and relevant measures for habitat improvement should be implemented. Habitat monitoring warrants continuation in all Pomeranian sites.