Habitats of the globally threatened Aquatic Warbler (Acrocephalus paludicola) in Pomerania — site conditions, flora, and vegetation characteristics
Tanneberger, Franziska; Bellebaum, Jochen; Dylawerski, Marek; Fartmann, Thomas; Jurzyk-Nordlöw, Sylwia; Koska, Ingo; Tegetmeyer, Cosima; Wojciechowska, Magdalena
Plant Diversity and Evolution Volume 129 No. 3-4 (2011), p. 253 - 273
published: Nov 1, 2011
ArtNo. ESP145012973004, Price: 29.00 €
The Aquatic Warbler is the only globally threatened passerine bird species in Europe. Around 1900, it was one of the most abundant birds in European fen mires. The population severely decreased as a consequence of extensive wetland drainage. In recent years, it has been rather stable in key breeding sites but has decreased sharply in its westernmost occurrence Pomerania. Conservation of the Pomeranian birds is of key importance for conserving the intraspecific diversity of the species. Throughout 2004-2006 we studied all current breeding sites of the species in Pomerania. Two areas have been studied in more detail: Rozwarowo Marshes, the largest breeding site in Pomerania, and Lower Oder Valley National Park, the last breeding site in Germany. Data on vegetation composition and height, water level, site conditions, and land use were analysed. The sites near the coast and in small river valleys are characterised by sparse and low Phragmites australis stands with a well-developed lower sedge and herb layer. The sites in the Lower Oder Valley are more nutrient-rich and dominated by Carex acuta, Phalaris arundinacea, and other meadow grasses. In Rozwarowo Marshes, the birds inhabit sparse, short Phragmites australis and Thelypteris palustris vegetation that is maintained by winter reed cutting. In the Lower Oder Valley National Park, Aquatic Warblers shifted from Caricetum gracilis to other plant communities that continued to be mown frequently. Similar to the Lithuanian Aquatic Warbler habitats in the Nemunas Delta and in contrast to the predominantly mesotrophic habitats of the core population, the Pomeranian habitats are eutrophic and more influenced by inundation. Various rare and threatened plant communities occur here. The Aquatic Warbler can be regarded as an umbrella species for mesotrophic and slightly eutrophic peatlands for which this bird is a specialist. Conservation activities should focus on a site-specific management and the prevention of further eutrophication.