Comparison of the Home Ranges of Mountain Hawk-Eagles during Different Phases of Wind Farm Construction

Abstract

Raptors are long-lived apex predators with a lower rate of breeding success than smaller birds. Therefore, their responses to the construction of wind farms must be documented to assess the impact of wind energy on birds. We estimated the home ranges of three pairs of Mountain Hawk-Eagle Nisaetus nipalensis orientalis before, during, and after construction of a wind energy facility to assess changes in home range. We also compared altitude, inclination, and land cover composition of habitats within home ranges during the construction phase. For one pair, the home range of which included wind farm construction, the distance from the home range to the construction area during the first year of construction increased significantly compared with that during pre-construction, but there was no significant difference between the post-construction and construction phase. It is thought that the construction of a wind farm within the home range caused the displacement, and that displacement began during the first phase of construction and continuing during the second phase and afterwards. Because the birds moved about 500 m away from the wind farm during the construction and post-construction phases but succeeded in breeding, we think that the distance of 500 m may be meaningful in terms of mitigating disturbance. The nest trees of all three successful breeding pairs were more than 1.3 km from the closest wind turbine, perhaps indicative that impact on breeding is light if construction takes place this far away from breeding sites. No significant differences in either land cover or inclination within home ranges were found during the construction phase, which might explain why all birds bred successfully during the second construction phase. After construction, all three pairs continued to use areas with similar habitat.