United States

United States

Collisions found to be minimal

A new report by the California Energy Commission concludes that no species of birds are threatened by the presence of wind turbines in the Tehachapi area, primarily because populations there are so much lower.

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The emotional issue of bird deaths in US wind farms has been put into better perspective with the release of a new report by the California Energy Commission (CEC). The report concludes that unlike in Altamont Pass, no species of birds are threatened by the presence of wind turbines in the Tehachapi area, primarily because populations there are so much lower. Deaths of protected species of birds in wind farms, particularly birds of prey such as eagles, has caused worldwide protests from ornithologists which have led to emotive public reaction on the issue.

In December, the CEC announced that a $250,000 grant from the National Renewable Energy Laboratory (NREL) would assist the agency in completing research in Tehachapi. Augmented by $500,000 from the CEC, the NREL grant would enable the agency to conduct research at San Gorgonio to document what the wind industry has been saying all along: that the much publicised avian mortality problem in the Altamont Pass wind farm region is site specific. California's two southern California wind resource development sites witness far fewer bird deaths associated with wind farms.

The CEC report notes that "the current level of scrutiny and caution exhibited during the permitting of new wind plant development results in costly delays and often costly studies. This is happening during a highly competitive period for electrical production companies." It goes on to note that "until there is a better understanding of the issue" concerns about avian mortality will persist and serve as a roadblock to new wind power development.

No dead eagles

The CEC report released preliminary results of research completed in 1995. The focus of this initial phase of inquiry, partially paid for by a $5,000 contribution from the American Wind Energy Association, was whether birds are, indeed, at greater risk when congregating near clusters of wind turbines.

The study indicates that some 200 species of birds use the Tehachapi wind resource area in any given year. Some 35 different species of birds were observed in a study area comprising 80% of the Tehachapi wind farming region and including turbines operated by Cannon Energy, FloWind, SeaWest and Zond. Over the course of six months, 28 dead birds were discovered representing 13 different species. No golden or bald eagles were among them, but other raptors, such as red-tailed hawk, barn and great horned owls, and American kestrels were found. Bird mortality in Tehachapi, however, is spread more evenly among species than in the Altamont Pass.

The highest number and most diverse collection of birds were found along the western ridge of the Tehachapi area, which is dominated by Zond's turbines. However, the highest rates of bird mortality were found on the eastern slope where the turbines of SeaWest predominate. Deaths were fewer in grassland areas and highest in habitats characterised by high desert shrubs.

The CEC calculates the level of mortality, and risk to birds, in several ways. One measure divides the total number of dead birds (28) by search sites (510) to arrive at an average "bird mortality" figure of 0.0549.

The report concludes that given the data collected to date, the risk to birds "does not increase as you get nearer to the developed wind resource area or a wind turbine. Birds in the Tehachapi wind resource area experience a greater risk of fatality as they near wind turbine facilities. This increase in risk, however, does not appear to represent a threat to bird populations, sensitive species, or general levels of birds using the area."

Dick Anderson, CEC manager of avian mortality research, hopes to delve into several aspects in the next round of research, including whether certain wind turbine designs can be correlated to increases in bird fatalities. Another goal of the research is to gather more information about why certain habitats appear more dangerous to birds when they are sites for wind farms. Field work in Tehachapi is continuing and will last through the end of this year. Field work at San Gorgonio will start in February and be completed at the end of 1998.

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