The objective of this project is to develop empirically testable predictions that can advance both shared predation theory and its application to biological control. The introduction of alien species into some areas has had a devastating impact on native biodiversity as they cause fundamental changes in ecosystems. Often eradication is impossible; however, it is necessary to control alien species in order to preserve the native species. In many European countries a catastrophic decrease in native prey numbers has been observed after American mink invasion. The proposed investigation will test hypotheses central to the pressing issue of the control of invading alien species. Our hypothesis considers reducing the magnitude and spatial scale of mink encroachment to national parks in order to protect water bird communities. The main goal of this project is to re-create and maintain areas where bird populations can survive in protected refuges on the basis of metapopulation and population dynamic theory. We will investigate the influences of density and demographic parameters of American mink population on mink dispersal into the National Park in relation to mink farm distribution and the effect culling operations in reducing mink compensatory response. The present project will also determine whether culling operations that are being implemented in Polish national parks have any impact on the population dynamics of mink. We will combine field surveys and non-invasive mink genotyping with an analysis of trapping records, sex- and age-structure models, and reproductive status of mink carcasses collected from culling operations in four Polish national parks situated in areas with and without mink farms. The main project output will be the establishment of efficient management strategies for birds affected by alien species, which can also be applied in other areas with similar problems.