6. Impacts of Wind Turbines on the Population and Nest Site Selection of the Montagu’s Harrier in North Frisia

In the following sub-study we looked at the nest site selection of Montagu’s harriers and their behaviour towards wind turbines in North Frisia and compared it to the behaviour of this species in the Hellweg Börde (see Chap. 5). The study area covers 960 km², subdivided into 198 diked polders, where nest sites of Montagu’s harriers were mapped between 1995 and 2006. For further analyses, the locations of nests were overlaid with the locations and data on the capacity of wind turbines within the same area. Besides known nest sites, we also included a reference group of random points into the data set. Linear mixed models were used to analyse the influence of wind turbines and some further environmental parameters (distance to potential foraging areas in salt marshes) on the nest site selection. In contrast to the Hellweg Börde, the number of Montagu’s harriers nests in the area increased slightly over the study period, while the number of wind turbines remained stable with a significantly increasing total capacity due to repowering. Montagu’s harriers in North Frisia showed no clear avoidance behaviour towards wind turbines in the selection of a nest site. The birds in North Frisia often selected areas for breeding and foraging, which were at the same time used as sites for wind turbines. Thus, the collision risk of Montagu’s harriers with wind turbines should not be underestimated (see Chaps. 4 and 14).