Eagles grow wise to wind farm hazards

The specter of bird fatalities has hung over the explosion in wind power over the last decade or so. Critics of wind tend to cite the now decades-old example of the Altamont Pass wind farm in California, where old versions of turbines are sited precariously close together, resulting in deaths to endangered birds like golden eagles. Estimates of just how many birds really die at the hands of a turbine have varied wildly, though a recent analysis pegged it somewhere between 140,000 and 328,000 per year.

New research, though, suggests that those very golden eagles made famous by failing to navigate Altamont may be a bit smarter about wind turbines than we thought. Researchers at the University of Northern British Columbia tracked 1,134 total golden eagles (between 327 and 427 per year) that flew near, past, over, and around a new wind farm in the eastern foothills of the Rockies in British Columbia. The first year they measured, 2009, counted as “pre-construction” before the turbines went up, while the subsequent two years were deemed “post-construction.” The birds, it turns out, aren’t so stubborn as to pay no attention to the giant spinning death traps that arose in their way. The findings appeared in the journal PLoS One.

In the pre-construction year, there were 60 flights across the ridge-top where the turbines would go up; of those, 20 flights went directly through the “risk zone,” meaning the height and position where a blade strike could occur. In the next two years, only nine of 148 flights across the ridge-top fit that description, a clear, statistically significant drop. And not only that, but the eagles seemed to avoid the danger zone even more carefully when the wind was up: 15 of the 20 risk zone flights in the first year occurred when wind speeds were high enough for a turbine to spin. Once the turbines actually went up, only three of those nine risky trips happened when the wind speed was high. In general, the raptors simply flew higher, up and over the turbines.

In other words, golden eagles may understand, at least to some extent, that flying through a blade zone of a 300-foot-tall wind turbine is generally a poor idea.

Of course, this doesn’t absolve wind power entirely when it comes to bird fatalities. It does suggest that siting wind farms in certain migratory pathways may have less impact than expected though; the researchers point out that wind farms placed where birds are more likely to just hang out rather than pass through—wintering grounds, say—may still be quite problematic. But considering that the world needs all the clean energy it can get, it’s good to know that an endangered species possesses some ability to let us off the hook for our contraptions dotting the landscape. – Dave Levitan | April 1 2014

Source: Johnston N.N., Bradley J.E., Otter K.A. (2014). Increased Flight Altitudes among Migrating Golden Eagles Suggest Turbine Avoidance at a Rocky Mountain Wind Installation, PLoS One, 9 (3) e93030. DOI: 10.1371/journal.pone.0093030

Image: shutterstock.com, zlikovec