Canadian Estimate of Bird Mortality Due to Collisions and Direct Habitat Loss Associated with Wind Turbine Developments

We estimated impacts on birds from the development and operation of wind turbines in Canada considering both mortality due to collisions and loss of nesting habitat. We estimated collision mortality using data from carcass searches for 43 wind farms, incorporating correction factors for scavenger removal, searcher efficiency, and carcasses that fell beyond the area searched. On average, 8.2 ± 1.4 birds (95% C.I.) were killed per turbine per year at these sites, although the numbers at individual wind farms varied from 0 - 26.9 birds per turbine per year. Based on 2955 installed turbines (the number installed in Canada by December 2011), an estimated 23,300 birds (95% C.I. 20,000 - 28,300) would be killed from collisions with turbines each year. We estimated direct habitat loss based on data from 32 wind farms in Canada. On average, total habitat loss per turbine was 1.23 ha, which corresponds to an estimated total habitat loss due to wind farms nationwide of 3635 ha. Based on published estimates of nest density, this could represent habitat for ~5700 nests of all species. Assuming nearby habitats are saturated, and 2 adults displaced per nest site, effects of direct habitat loss are less than that of direct mortality. Installed wind capacity is growing rapidly, and is predicted to increase more than 10-fold over the next 10-15 years, which could lead to direct mortality of approximately 233,000 birds / year, and displacement of 57,000 pairs. Despite concerns about the impacts of biased correction factors on the accuracy of mortality estimates, these values are likely much lower than those from collisions with some other anthropogenic sources such as windows, vehicles, or towers, or habitat loss due to many other forms of development. Species composition data suggest that < 0.2% of the population of any species is currently affected by mortality or displacement from wind turbine development. Therefore, population level impacts are unlikely, provided that highly sensitive or rare habitats, as well as concentration areas for species at risk, are avoided

Comparing pre- versus postoperational movement of nocturnal migrants around a wind energy facility in northeast British Columbia, Canada

We used two data-recording, open-array marine surveillance radars to track microscale movements of nocturnal migrants at a wind energy project in northeast British Columbia during the preoperational (2008-2010) and operational periods (2011-2012). Data was collected during the peak periods of spring and fall passerine migration in each year. We measured bearing and altitude of nocturnal migrants, as well as the average number of migrants flying in the airspace closest to the wind turbines. Using weather data on wind direction and strength during the periods of monitored migration, we calculated flow-assistance of wind in aiding migration. Although there was greater flow-assistance to movement in spring over fall migration, we did not find a significant difference between the preoperational and operational periods in flow-assisted flight. The altitude at which migrants flew did differ with development phase of the wind facility; migrants flew at higher altitudes during years when the turbines were operational compared to preoperational years. Although the proportion of migrants detected in the airspace 0-150 m above ground level (agl), coinciding with turbine height, did not differ with season or operational phase of the installation, there was a reduction in the proportion of migrants in the airspace just above turbines (151-300 m agl) when turbines were operational. In general, though, the overall altitudes used by migrants were typically higher than turbine height, so the adjustments we documented would only further reduce what appear to be already low levels of collision risk at this particular facility. We discuss possible reasons why this facility appeared to induce low collision risk to migrants, and how this might inform siting decisions of other wind facilities