BSBO Statement on Study Painting One Wind Turbine Blade Black

​​A recently released scientific paper based on work done in Norway seems to suggest that bird deaths at wind turbines can be significantly reduced by painting one of the three blades black and leaving the other two white/gray so as to make them more noticeable to birds in flight.  There has been a flurry of optimism over the study and its potential impact on the use of wind turbines as a renewable energy source.  We think this optimism is overstated, and would like to set the record straight.

First, the idea of painting turbine blades to reduce bird deaths was published in 2003 by the University of Maryland in conjunction with National Renewable Energy Laboratory in Colorado.  This study set the groundwork for the principles behind the Norwegian study.

The conclusions of the Norwegian study were that death rates were reduced by over 70% at the painted turbines; but this needs to be tempered by the facts of the study.  First of all, it was a small study, looking at fatality results of only four painted turbines and four adjacent unpainted ones.  The authors of the study readily admit the small size of the study warrants that the study be repeated with a larger sampling of turbines in order to verify their results.

Secondly, the raw data appears to show a positive effect on bird deaths, which were primarily confined to white-tailed eagles, not other species.  But even these results are inconclusive due to small sample size.  In fact, if all the data are considered, including the data excluded by the authors of the study, the results are just the opposite: bird deaths increased with the painted turbines.  

Additionally, the majority of birds killed by turbines are species other than raptors, and many of these may be killed during nocturnal migration when painting blades could not be expected to have any effect.  Further, some species are predominantly killed by the stationary blades of turbines while the turbines are not operative or even the turbine tower.  Even if the painting works eventually, its overall effect on most species is unknown at this time.  Perhaps these are reasons why the work done in 2003 has languished for almost 20 years and still has not come to practical fruition.  So, painting the blades is certainly not a panacea for bird deaths at turbines.
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Finally, here in the U.S., it is an FAA regulation that turbines and blades can only be painted white or light gray in order to ensure their visibility to low flying aircraft; otherwise the turbines are required to have daytime lighting.  So, for the time being, painting one blade black seems a moot point.

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