Commercially cut reed as a new and sustainable habitat for the globally threatened Aquatic Warbler

Abstract

The Aquatic Warbler (Acrocephalus paludicola) is a song bird breeding in fen mires and similarly structured other wetlands with a water depth of 1-10 cm. Widespread in central-European wetlands at the beginning of the 20th century, the species is now globally threatened. The westernmost and genetically distinct Pomeranian population is even on the verge of extinction. The major challenge in the conservation of remaining habitat is the costefficient removal of biomass. About 50% of the Pomeranian population survives in a valley fen near Rozwarowo in Northwest Poland, where between 1993 and 2007 a conspicuous change in breeding habitat has taken place from summer grazed sedge meadows to commercial winter cut reed beds. We compared vegetation structure, site conditions, and potential prey abundance with the distribution and abundance of Aquatic Warblers in Rozwarowo Marshes and studied temporal changes and the compatibility of conservation and reed cutting interests. Aquatic Warblers now occur almost exclusively in sparsely growing, low reed with abundant Thelypteris palustris, Carex elata, and Lysimachia vulgaris. This vegetation type provides more potential prey for Aquatic Warblers than the higher productive tall reed, whereas the patches of sedge vegetation have become too small following succession after abandonment. Currently, commercial reed cutting maintains suitable Aquatic Warbler breeding habitat. Considering the impending changes in the reed market, there is a need for flexible agri-environmental schemes (AES) to ensure that stripes are left uncut and to prevent eutrophication by high and long flooding of the site.

Song Post Selection in the Aquatic WarblerAcrocephalus paludicola

“…On the Kramskie marshes (site 17) a large population (300 males in 1972) disappeared within 20 years due to drainage of the main nesting area (Winiecki 2000). At some other sites natural succession (encroachment of reed, birches, willows and other tall vegetation) accelerated by land abandonment and decline of water table may constitute an important threat for specific stage of plant succession preferred by the Aquatic Warbler (Tanneberger et al 2009, see also Kozulin et al 2004). In the Biebrza valley this process started a …”

Water on the Fen Mire as a Problem in the Protection of Globally Threatened Species: Long-Term Changes in Aquatic Warbler Numbers

“…Water affects the accessibility of nests to predators, the composition and abundance of food resources, and, hence, breeding success [3,7,11]. Although AW has been the object of a many investigations during the last 20 years [7,[11][12][13][14][15][16][17][18][19][20], the relevant literature does not boast a set of long-term data gathered every year on the same area, especially in the context of water-level changes. In fact, even though these studies could have great importance for the conservation planning of the species in Europe, the analysis of such long-term data on changes in AW numbers and water-level records is a problem that has yet to be addressed.…”

Effects of fen management on bird communities in north-eastern Germany

“…Especially grassland species had to suffer severe losses mainly due to the intensification of grassland management, including, e.g., drainage, several cuts per year, high levels of fertilization and conversion into arable fields (Vickery et al 2001;Newton 2004;Young et al 2005). On the other hand, the abandonment of unproductive grassland and subsequent habitat deterioration through secondary succession may cause serious problems for species requiring open habitats such as traditionally managed wet meadows (Tanneberger et al 2009. As a result of both reduction in grassland quality and total area, extensively managed grassland has become rare in many countries, threatening the existence of entire species communities (Busche 1994;Vickery et al 2001;Donald et al 2002;Roodbergen et al 2012).…”