Wind Turbines and Birds

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Wind turbines powered by a coastal breeze. Andrew Watson/Photolibrary/Getty

Interest in renewal energy has been rising; dramatic visual evidence of this includes the large number of wind turbines popping up on the landscape across North America. These structures, unfortunately, are not free of environmental harm. In the early days of industrial wind farms, poorly located turbines have led to significant bird mortality events, particularly affecting raptors. Since then much attention has been focused on determining whether wind turbines can be safe for birds.

Wind Turbines Are Not Safe for Birds

The short answer is no, many birds die as a result of collisions with the tower and wind blades. There is evidence that some raptors are learning to avoid the spinning turbines, but song birds migrate at night and continue to be hit by the blades. What has been more difficult to determine, however, is whether this source of mortality significantly affects wild bird populations. A study published in September 2014 provides the clearest answer yet.

Focusing on passerines (commonly referred to as song birds), the authors compiled data from 116 separate studies, corrected the results for biases (for example, surveys below wind turbines will only detect a proportion of killed birds). The authors then carefully extrapolated the fatality rate to the entire wind farm inventory in North America.

Mortality Estimates in Perspective

The study, published in the peer-reviewed scientific journal PLOS ONE, features an estimate of 368,000 birds killed annually by wind turbines.

That is a lot of birds, but how does it compare to other sources of mortality? In another study, communication towers (for example, television towers) are blamed for 6.6 million passerine bird deaths annually. Feral and domestic cats kill 1.4 to 3.7 billion birds a year. To further put wind turbine kills in perspective, the turbines’ take is less than five hundredths of one (<0.05%) percent of the population.

The most affected species, based on number of kills and continent-wide population size, include Black-throated Blue Warbler, Brown Thrasher, Horned Lark, and Tree Swallow.

This paper comes as good news for wind energy proponents, but it should remain clear that wind turbines do kill birds. While other sources of mortality dwarf the effects of wind energy at the continental scale, poorly positioned turbines can have disproportional impacts and reduce bird populations locally. It can also be an additional stressor on some species already severely threatened by many other issues. Finally, it is also important to note that this study focused on passerine birds. More acute problems have been documented for some other groups of birds, notably raptors and some grouse species. 

Source

Erickson et al. 2014. A comprehensive analysis of small-passerine fatalities from collision with turbines at wind energy facilities. PLoS ONE: DOI: 10.1371/journal.pone.0107491