Bird Deaths at Wind Farms (Part 5)

2013 Canadian Bird Mortality Study

In 2013, J. Ryan Zimmerling, Andrea C. Pomeroy, Marc V. d'Entremont, and Charles M. Francis published their study: Canadian Estimate of Bird Mortality Due to Collisions and Direct Habitat Loss Associated with Wind Turbine Developments. 

The abstract of the study states: 

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.

The researchers estimated direct habitat loss based on data from 32 wind farms in Canada. On average, wind farms caused total habitat loss per turbine of 1.23 hectares (ha), which corresponded to an estimated total habitat loss due to wind farms nationwide in Canada of 3635 ha. 

Based on published estimates of nest density, this loss could represent habitat for  about 5,700 nests of all species. If the researchers assumed that nearby habitats were saturated, and that the wind farms displaced two adult birds per nest site, they concluded that the effects of direct habitat loss were less than that of direct collision mortality. 

If installed wind capacity increases more than 10-fold over the next 10-15 years in Canada, as predicted, the researchers estimated direct mortality of approximately 233,000 birds/year, and displacement of 57,000 pairs through habitat loss.