Avoidance

VI.   Avoidance:  Methods to Reduce Risk

Below is a conglomeration of possible methods, practices and policies that could potentially reduce the risk to both bat and avian species.  The possible benefits of these methods are separately outlined for the respective benefits to bats and birds.  Most of these methods reflect general benefits, and do not necessarily show benefits for individual species. 

The methods outlined below are paraphrased from the variety of resources used in our discussion.

Bats

-       Reduce wind turbine operation times when wind speeds are low.  Because lower wind speeds reduce the amount of energy that can be generated, it is not necessary to operate all turbines in an operation at once.  Furthermore, bats are more likely to be active during periods of low wind speeds.  Reducing or ceasing operation during times of low wind speed will reduce the overall risk potential to bats because it is presumed that more bats will be active during such conditions.  (National Wind Coordinating Collaborative, 2010)

-       Reduction of blade speeds could produce fewer alterations to the surrounding airspace’s air pressure.  Few alterations to air pressure could lead a decreased risk of barotrauma.  (Fish and Wildlife Service, 2004)

-       Use of ultrasonic devices that project frequencies proven to deter bats.  Because bats use echo-location to navigate, ultrasonic devices may be the best possible method to reducing bat mortalities.  (Fish and Wildlife Service, 2004)

Birds

-       An effect known as “motion smear” is known to decrease the ability for birds to identify spinning wind turbines.  It has been suggested that using alternative paint colors (such as yellow or red), or the use of ultra-violet (UV) paint may reduce collision rates.  (National Wind Coordinating Collaborative, 2010)

-       Use of devices known as “laser bird-alerting” devices that are currently used to deter birds from airports of energy distribution infrastructure.  (Fish and Wildlife Service, 2004)