Assessment of Avian Mortality from Collisions and Electrocutions


Title: Assessment of Avian Mortality from Collisions and Electrocutions
Publication Date:
June 01, 2005
Document Number: CEC-700-2005-015
Pages: 48

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Dorin, M.; Speigel, L.; McKinney, J.; Tooker, C. (2005). Assessment of Avian Mortality from Collisions and Electrocutions. Report by California Energy Commission. pp 48.

Safeguarding endangered and protected avian species is an increasingly important component of both California’s development of electric generation and the siting and operation of power lines. Bird deaths from electrocution and collision with wind turbines and power lines are an ongoing environmental issue affecting wind energy development and the siting and operation of electrical transmission and distribution lines. Wind energy is a major part of the renewables portfolio standard (RPS), and wind developers rely on federal and state tax credits to help offset costs of new development. However, high wind areas are also prime habitat for certain protected bird species. Major wind developments in Altamont Pass, San Gorgonio, Tehachapi Pass, and Solano County have caused numerous bird deaths. To resolve issues with current wind resources and accommodate additional wind development and repowering, mitigation and/or avoidance is needed to reduce avian mortality.


When birds and bats collide with electrical power line infrastructure, their electrocution also can result in electrical outages, affect service reliability, and cause wildfires. Most bird species being killed are protected under state and federal laws and are thus of concern to the public at large, as well as environmental and wildlife law enforcement officials.


This staff paper issued in conjunction with the 2005 Environmental Performance Report examines the ongoing issues of avian fatalities from electrocution and collision with energy structures. This paper includes current research results, information provided from the utilities, research conducted through the Public Interest Energy Research (PIER) program and a brief look at how some other states are addressing energy infrastructure-related avian fatalities. This paper is divided into two chapters: the first discusses avian fatalities in relation to wind energy resources and the second, avian fatalities in relation to electrical transmission and distribution lines.


There are several trends in California wind energy development and associated avian issues. Among them are research shifting from identifying the extent of the avian collision problem to resolving it, the discovery that bat fatalities may be an issue in at least one wind resource area, and how mitigation for projects is determined and applied. The rates of bird use and collision differs in other wind resource areas in California. California’s Altamont Pass Wind Resource Area stands out as having a high bird fatality problem due to the combination of approximately 5,000 operating turbines and a high concentration of year-round raptors. Alameda County continues to implement a moratorium on developing additional wind development in the Altamont Pass until avian fatalities can be reduced. Solano County also has a high rate of collisions, while San Gorgonio and Tehachapi Pass have lower rates. More recently, studies at wind farms have identified bat fatalities as an issue. In Solano County, surveys for bats have been conducted confirming bat fatalities are an issue there. Elsewhere in California, bat fatality studies have not been conducted and, therefore, the extent of the problem in these wind resource areas is uncertain.


Wind turbines should be sited in areas that reduce impacts to birds and other species as well as critical habitat. Mitigation measures should also be developed for all of the wind resource areas and applied to existing and new development to effectively lessen impacts on avian resources. Applying measures that reduce the chances of avian interactions with wind turbines and electrical infrastructure is the only way to reduce collisions. Voluntary guidelines for surveys and mitigation measures exist, but industry and local agencies do not implement them consistently between projects.


Avian fatalities due to collisions with and electrocutions from electrical power lines in California cannot be accurately quantified although they can be reduced using birdsafe designs. In some areas the utilities collect information on avian interactions with transmission lines and have adopted an Avian Protection Plan. The data collected are not normally publicly reported, except when federally listed species are reported to the U.S. Fish and Wildlife Service. However, one recent study in Arizona showed that 85 percent of avian interactions with electrical power lines go undetected by the utility (Dwyer 2004), although they still critically injure or kill the bird. Therefore, the information collected by the utilities maybe grossly underestimating the impacts to avian resources in California.


The PIER Environmental Area (PIER–EA) is collaborating on current research to help quantify the problem as well as resolve it through identification of mitigation measures and dissemination of information to stakeholders. There are other guidance documents available that utilities use to lower the potential for electrocutions and collisions with power lines. The guidelines are voluntary and the extent of their implementation differs throughout the state.

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