Abstract
To study the potential impact of wind turbines and associated structures on Montagu's harriers Circus pygargus, we located 111 nests over five years (18-28 nests per year) and compared their distances to several features (natural and anthropogenic) between wind farm pre- and post-construction periods using a before-after (BA) study design. We analysed abundance and density of nests and colonies through the study period. We also fitted a predictive model of nest occurrence using distance-to-feature variables and habitat as predictors. Lastly, Montagu's harrier fatalities from collision with wind turbines were estimated. No differences were detected between pre- and post-construction periods in nest or colony abundances. We found that harriers nested closer to the locations of wind turbines and power lines after wind farm construction, although distance to closest track did not change. We detected a higher spatial aggregation of Montagu's harrier nests after wind farms were installed, when the distribution of nests was mostly explained by habitat and distance to the closest track. Distance to wind turbine was apparently not influential. Fatality through collision was relatively uncommon during the study period. Our findings demonstrate that the construction, operation and maintenance of wind farms did not seem to adversely affect Montagu's harrier nesting decisions in our study area. However, we encourage further studies including reproductive parameters and foraging strategies of Montagu's harrier to provide a complete investigation of potential impacts of wind farms on this species.