Assessing dispersal potential: A case study of the little owl (Athene noctua) in south-western Germany and northern Switzerland

As a consequence of human encroachment upon natural ecosystems, the world is facing biodiversity loss at an unprecedented rate. Thus, nature conservation is urgently required to prevent species extinction. Conservation management can only succeed, however, if the protection measures are based on sufficient understanding of the ecology of the target species. One important element thereof is potential dispersal with regard to the connectivity of suitable habitats across a landscape. Here, I study natal dispersal of the little owl (Athene noctua) in the south-western German state of Baden-Württemberg and northern Switzerland with the objective of analysing potential dispersal pathways and barriers. The analysis uses radio-telemetry data of juvenile little owls, collected between 2009 and 2011. I first performed a statistical analysis of the data to infer habitat preferences. The estimated habitat suitability map provided the basis for a spatially explicit individual-based simulation model, which was developed to simulate little owl dispersal movement. Parameter calibration was achieved using Approximate Bayesian Computation. I find that the dispersal movement behaviour of little owls exhibits more or less distinct inter-individual and -sexual differences. The results also indicate that substantial dispersal barriers are represented by major topographic landscape features in combination with specific dispersal movement behaviour. Despite the fragmented landscape, it seems likely that the three little owl populations in Baden-W¨urttemberg continue to expand. However, the area between the southwestern German little owl populations and the habitat patches in northern Switzerland appears to have low permeability. I conclude that conservation efforts concerning the little owl should focus on areas that are functionally connected to already populated habitat patches. Furthermore, I believe that the approach used in this study is a useful method to assess species-specific dispersal potential with regard to landscape connectivity.