Ingrid Kohl

Habitat requirements and territory size in an isolated population of Redspotted Bluethroat (Luscinia svecica svecica) in the Austrian Alps

The Redspotted Bluethroat (Luscinia svecica svecica) is widely distributed in Siberia and Fennoscandia. In the 1970ies, an isolated population was discovered in the Austrian Alps at Hundsfeld Moor (Province Salzburg), which still represents the largest known local population in The Alps (10-21 breeding pairs per year). This study analysed the habitat requirements of L. s. svecica at Hundsfeld Moor as contribution to understand the highly patchy distribution in Central Europe as opposed to the rather continuous northern distribution range of this subspecies. The survey of the population at Hundsfeld Moor and its vicinity was conducted between May and September 2005. A variety of habitat variables (extracted from aerial photographs) were tested for their potential to affect the occurrence of bluethroats. Mountain pine (Pinus mugo) area and perimeter, area of roads as well as habitat heterogeneity (Shannon index) were significantly higher in bluethroat territories compared to randomly selected plots. Additionally, we tested effects of habitat variables on the number of 25 m x 25 m subgrid cells occupied by bluethroats. The same habitat variables were identified as important requisites for bluethroat occurrence at different geographic scales. Territory size was neither related to the measured habitat parameters nor habitat heterogeneity. The number of neighbouring territories was positively related to territory size. Possibly due to spatial limitation through neighbouring territories habitat heterogeneity proved to be higher in territories with more neighbours. Results from this study can be used for the development and the implementation of more effective management strategies for the local population of Redspotted Bluethroats in the Hundsfeld Moor. Further studies on other populations in Central European mountain ranges have to verify these conclusions.