Micro-scale Movements of Nocturnal Migrants Around a Wind Energy Facility in Northeast British Columbia, Canada During Pre-operational and Operational Periods

We investigated the passage of nocturnal migrants at a wind energy project in northeast British Columbia during the pre-operational and operational periods using two open array marine surveillance radars from 2008 to 2012.... [ view full abstract ]

We investigated the passage of nocturnal migrants at a wind energy project in northeast British Columbia during the pre-operational and operational periods using two open array marine surveillance radars from 2008 to 2012. Micro-scale movements were examined as the deviation between average hourly track bearings of nocturnal migrants and the average wind vector on a nightly basis, the average hourly altitude of migrants and the average hourly number of migrants flying in the airspace closest to the wind turbines. In general, passage rates and flight trajectories did not significantly change between the pre-operational and operational periods, suggesting there was little effect on migratory directionality from the presence of wind turbines. Despite variations in wind conditions between seasons, migrants showed consistent directionality and general trends of broad-front migration patterns. The altitude at which migrants flew did differ with development phase of the wind facility, with migrants flying at higher altitudes during years when the turbines were operational. In general, though, the overall altitudes used by migrants were typically higher than turbine height, so the adjustments we documented were further reducing the current low levels of collision risk. In conclusion, at the micro-scale level nocturnal migrants were not significantly adjusting their movements around the wind energy facility during the operational period and their typical migratory behaviour did not place them in potential collision risk situations.