Wind farms have unintended negative consequences for birds, such as bird collisions, habitat loss, and barrier effects. Japanese law now requires environmental impact assessments (EIAs) of wind farm construction. Despite these EIAs, assessments of wind farm effects on birds are often inadequate because no data are available that compare bird behavior and distribution before and after wind farm development. Here we investigated macro avoidance and the foraging distribution of swans before and after the construction and onset of operations of a wind turbine operation in Japan’s Tohoku region. During the spring and fall migratory seasons, we used fixed-point observations to survey swan flight trajectories near a newly constructed wind farm and an existing, operational wind farm. Swan turning radius and trajectory altitude were used to determine macro avoidance of wind farms. Swan foraging distribution around wind farms was surveyed by car. Sightings of migratory swans drastically decreased in the wind farm areas, but swan foraging distribution around the turbines remained unaffected. This outcome may be because the wind farm is distant enough from existing swan foraging areas. We conclude that collision risk should be low because migrating swans avoided wind turbines, but their traveling distance is increased by the need to fly around the wind farm area.
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