Bird Fatalities: 1.7 Birds Per Turbine AnnuallyMark Ohrenschall
Con.Web, September 29, 2003
Stateline Wind Project Bird Deaths Estimated
at 1.7 Birds Per Turbine Annually, Report Shows
Stateline Wind Energy Center has killed an estimated 1.7 birds per turbine annually, a slightly lower fatality rate than for other U.S. wind projects, according to recently published preliminary findings.
Stateline's first avian and bat monitoring program report documented 106 bird deaths and 54 bat deaths on standard search plots around representative turbine groups between July 2001 and December 2002. Those numbers were extrapolated to come up with fatality estimates for the entire 399-turbine wind farm, which straddles the Oregon-Washington border southwest of Walla Walla.
Horned larks were the predominant victims, accounting for 43 percent of found bird fatalities. No threatened, endangered or candidate bird or bat species--at the federal or state levels--were discovered as casualties of the world's largest land-based wind farm.
"It generally confirmed what [Stateline developer] FPL [Energy] has been asserting all along, that it is a relatively low-use area for avian species," said John White of the Oregon Department of Energy.
The report said Stateline's fatality estimates could actually be high, as they include many birds with an undetermined cause of death. FPL believes the fatalities represent a tiny fraction of the total birds in the Stateline vicinity.
"We were pleased the number was below the average estimated for other projects," said FPL Energy's Anne Walsh, noting this report is part of an ongoing bird and bat monitoring study through 2003. "We'll continue to work closely with the agencies and the local Audubon Society to review the final results," she said.
Careful turbine siting is the biggest factor in limiting bird deaths at wind farms, according to the American Wind Energy Association. An AWEA publication lists other and far greater causes of bird deaths: house cats, which kill an estimated 100 million birds annually in the U.S.; collisions with plate glass, which cause an estimated 97.5 million bird deaths each year; and collisions with vehicles, which lead to 57 million dead birds annually. AWEA also cited a study estimating 3,000 bird deaths at a Florida coal-fired power plant one night during fall migration.
As part of the monitoring program, WEST Inc. and Northwest Wildlife Consultants personnel searched for carcasses around 41 representative turbine plots effectively consisting of 146 total turbines. More than 2,200 separate searches were conducted between July 2001 and December 2002, the report said.
Trained searchers recorded the number of intact and scavenged bird carcasses, along with sitings of 10 or more feathers in one spot. "All bird casualties observed within the search plots were included in the fatality estimates, unless cause of death could be determined, and this cause was not related to the wind facility," the report said. "True cause of death is unknown for most of the fatalities." Other potential causes likely include vehicles, raptors and weasels.
The report also used statistical methods to gauge searcher efficiency and carcass removal rates, in deriving estimates of bird deaths.
WEST Inc. concluded that the 399 Stateline turbines caused an estimated 1.68 bird deaths apiece on an annual basis, slightly less than the 1.82 average estimate for other U.S. wind projects listed in a 2001 report.
Overwhelmingly the most common bird victim, by species, was the horned lark, described in the report as "a common resident songbird" and later by FPL as the most abundant local species. The report documented 46 horned lark deaths, 43 percent of the bird total. "I don't think I've had a satisfactory explanation" for that finding, said Shirley Muse of Blue Mountain Audubon Society, although she noted horned larks find "ideal habitat" in the area.
None of the other 26 bird species found as casualties exceeded six recorded deaths. Six raptors were discovered dead, including four red-tailed hawks. Small birds accounted for an estimated 1.52 deaths per turbine per year, and large birds an estimated 0.16 deaths per turbine per year.
Turbines in the middle of rows had "statistically significant[ly]" more bird deaths than turbines at the end of rows, the report said. Lit turbines had more dead birds around them than unlit turbines, although the difference was minimal. Bird carcasses were found an average of about 100 feet from the nearest turbine.
The report also documented 54 bat deaths around turbines, slightly less than one fatality per turbine per year--lower than found in other new wind projects, but higher than neighboring Vansycle Ridge Wind Farm.
In addition to searching for carcasses, field observers also recorded living birds in the vicinity. Horned larks accounted for more than half of 2,262 recorded birds, while Western meadowlarks and Canada geese also were commonly seen. Given the relatively brief periods for these observations, said FPL, "It is a reasonable conclusion that the estimated number of fatalities at the project comprised an extremely small percentage of the number of birds that spend time in and near the project area."
Extensive wildlife studies before Stateline's construction helped determine where to put turbines, according to FPL's Walsh. "We worked with the government officials and we had consultants, specialists and we worked also with the local Audubon Society to look at the siting locations," she said.
AWEA also stresses the importance of siting. "Studies to date indicate that the most important action to take in reducing bird deaths at wind energy plants is to carefully evaluate proposed sites before wind turbines are installed," the trade group said. For example, turbines at a Wyoming wind farm were placed away from a mesa rim where raptors were found to be frequent fliers.
Muse, of the local Audubon Society, said her organization supported Stateline's local governmental approval, although it had a few specific concerns. One was the proposed location of a turbine string near McNary National Wildlife Refuge, which is popular with migrating waterfowl; FPL left out the string, she said, and further research, including nighttime radar studies, showed bird deaths would not be a huge problem. Auduboners also worried about a ferruginous hawk nest, which Muse said has since been abandoned, though for unclear reasons. Ferruginous hawks are listed as a threatened species in Washington.
She said she doesn't like the fact birds are killed by wind farms, but she noted her car sometimes accidentally hits birds, and her now-deceased cat ate birds.
Muse said she prefers renewable wind to fossil-fueled and nuclear-powered energy, and southeastern Washington/northeastern Oregon is a windy place. "The birds and the turbines need the same habitat," she said. "To me, what you have to work on is to do the best job you can and not go into places where there are clear dangers to birds."
Wind developments have improved in coexisting with birds, she said, with, for example, the advent of tubular towers that minimize perching opportunities and spread-out turbine strings that allow birds to fly more easily between wind machines.
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