Leading Bird Conservation Group Formally Petitions Feds to Regulate Wind Industry

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10. Here’s a fascinating study

http://www.nrel.gov/wind/pdfs/28591.pdf

[font face="Times, Serif"][font size="3"]March 2002 • NREL/SR-500-28591[/font]

[font size="5"]An Assessment of the Impacts of Green Mountain Power Corporation’s Wind Power Facility on Breeding and Migrating Birds in Searsburg, Vermont[/font]

[font size="4"]July 1996–July 1998[/font]

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[font size="3"]Chapter 7. Avian Fatality Study[/font]

[font size="2"]Introduction[/font]

The development of wind power in the northeastern United States is in its infancy. As projects are proposed, several questions relating to environmental issues are posed. The primary question is, "Do wind turbines kill birds, and, if so, how many?" There is a long history of birds flying into tall towers of various sorts (see Chapter 2), including wind turbines (Colson & Associates 1995, Orloff and Flannery 1996, Winkelman 1995). However, because wind turbines are such a new development on the landscape, answering these questions is still not easy. We are learning that in most situations turbines kill few birds. Recent studies by Anderson (in press) in California, Winkelman (1994, 1995) in the Netherlands, Strickland (in press) in Minnesota, and Kerlinger and Curry (in progress) in Colorado are studies that are now being conducted or recently completed suggest that small numbers of birds are killed. In fact, there is only one site where the kills are considered egregious and that site is the Altamont in California, where nearly 5,400 turbines now stand. The actual numbers killed in the Altamont do not exceed one bird per turbine per year and rates of between 0.05 raptors per turbine per year (Orloff and Flannery 1992, 1996) and 0.019 raptors per turbine per year (Kerlinger and Curry 1998) have been reported.

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Fatality Searches. In a total of 21 search periods (1 search period equals four turbines searched) not one dead bird was located in the Searsburg wind power facility (Table 7.1). These observation periods were conducted on 15 different days and consisted of about 41 hours of search time. On some days two search periods were used. This represents a total of 82 searches conducted under individual turbines during four (five if August is included) months. (The number of search periods is more than the number called for in the original proposal (N = 6) that was approved by NREL. The extra searches were done after consulting with other biologists and realizing that more were needed to insure that the observations were reliable and valid indicators of actual fatality rates. In addition, no dead birds were found by workers at the wind power plant since it went on-line in spring 1997 and during the previous autumn (1996) when turbines were erected and some were working.

Scavenging Rate Determination. Two tests of scavenging were conducted. Scavenging was minimal as indicated by the small numbers of birds that disappeared from where they had been placed. In the first and shorter of the two, short-term disappearance was observed. Of twenty birds placed beneath turbines on June 30, 15% (N = 3) had disappeared by July 2. These birds were checked again on September 2 at which time only 4 (20% of original birds) were located. Those that were relocated included Blue Jay, Slate-colored Junco, Gray Catbird, and a Yellow- rumped Warbler. They were all decomposed and were not easily found as feathers had matted down and lost all color as a result of photo-oxidation and perhaps washing by rain with low pH. This shows that some birds disappear quickly, but scavenging is not the same at all sites nor in all seasons. Scavenging may have been even less than 80% during the 2 month period because some carcasses may have simply been overlooked as a result of decomposition and growth of grass and shrubs which act to make carcasses less visible.

For birds placed out on September 2, 20% disappeared during the first week and another 15% disappeared about a week later. At the end of a month (about 5 weeks/scavenging surveys), 65% of the birds remained. There was no scavenging after the second week. Again, scavenging occurred, but it was not thorough.

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[font size="2"]Discussion and Conclusions[/font]

The most important finding in this study is that not one dead bird was found beneath the turbines at Searsburg in 1997. The fact that no birds were found dead in the area around the turbine towers may not mean that the turbines cause no fatalities, although it strongly suggests they are not killing large numbers of birds. Because this is the first study of fatalities at an operating wind power facility in the eastern United States, the results should not be generalized to all situations in this area.

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