Habitat use of flying subadult White-tailed Eagles (Haliaeetus albicilla): implications for land use and wind power plant planning

Abstract

Large-scale construction of wind power plants may threaten large raptors at both individual and population levels. The most efficient way to prevent the negative effects of wind power plants is to avoid building on presumably high-risk sites, which requires an understanding of the movement patterns and habitat use of vulnerable species. The White-tailed Eagle (Haliaeetus albicilla) is vulnerable to wind energy in terms of both collision mortality and displacement due to disturbance. We used satellite transmitters to study the movements of juvenile and sub-adult White-tailed Eagles. We developed a Resource Selection Function (RSF) to model their habitat use at the Finnish coast, which holds about 80% of all planned and constructed wind power plants in the country. In addition, we made a collision risk assessment by calculating how likely areas are to be visited by a flying White-tailed Eagle at both planned and existing wind-farm areas. Our resource selection model predicted 83% of the observations correctly. We found that sub-adult White-tailed Eagles preferred areas close to their natal sites, the coastline and archipelagos. They avoided the open sea, urban areas and other constructed areas such as cottages, industrial areas and agricultural fields. The White-tailed Eagles flew lower over the sea (median 20 m) than over land (median 80 m), and time spent flying at risk heights (50–200 meters) was greater over land (28%) than over the sea (19%).