Studier av habitatval och revirstrukturer hos vassångare (Locustella luscinioides) i Tåkern

Sammanfattning: The Savi’s Warbler (Locustella luscinioides) is a recently established bird species in a few reedy shallow lakes of southern Sweden and has only been found nesting for the last twenty years. Little is known about the species' habitat preferences, breeding biology and demands for specific territory structures at breeding sites in Sweden. Knowledge of a newly established species’ habitat requirements is essential to maintain a viable population and design action plans. This study, the first of its kind in Sweden, examined the vegetation structures in occupied territories of Savi’s Warblers at Lake Tåkern, the country's stronghold for the species. The species was found to be associated with the outer edge zones and fragmented areas of reed (Phragmites australis). Occupied territories differed from randomly chosen unoccupied (control) territories by having a thicker layer of reed litter, and on average more bushes of Willow (Salix spp.) present. Reed density and reed height did not differ from areas that lacked Savi’s Warblers. Territorial and displaying males were concentrated in two edge areas with a mosaic of reed islets where the territories remained relatively close together.