Modelling golden eagle habitat selection and flight activity in their home ranges for safer wind farm planning

Onshore wind farm development may impact vulnerable large eagles at both individual and population levels and requires appropriate assessment under the EU Bird and Habitat Directives. The present conservation policy (e.g. fixed safety zones around nest sites) improves species conservation but may not prevent habitat loss or reduce collision risk in the best possible way because this policy may not consider habitat-specific effects on eagle behaviour. Here, we develop a method for estimating habitat use and flying time distribution within Golden Eagle (Aquila chrysaetos) home ranges. Location data retrieved with GPS-transmitters (Global Positioning system) in Finland indicated that these large raptors used vast areas (mean 297 km2, 95% Minimum Convex Polygon), reaching up to 14 km, but not uniformly around their nests. The best resource selection function models (cross-validation performance 83%) revealed that flying Golden Eagles preferred the vicinity of their nests, steep slopes, and old forests in their home range. They avoided human settlements and neighboring territories. GPS data indicated short flying times per day (mean 2.2 h) and about 30% of the flying time within collision risk heights (50-200 m). Together with information on habitat selection, flying times can be used for predicting airspace use of birds and in assessing the collision risk at particular wind farm locations. Thus, our method can be applied in planning wind farm locations that enable a safer co-existence of large territorial birds and wind power plants in the same landscape.