SEATTLE - Biologist Orah Zamora spends her days walking around wind turbines in search of dead birds and bats. Most of her surveys turn up nothing, but every once in a while she finds a carcass that may have been felled by a whirring blade.
“It’s like a crime scene, and you try to figure out what happened. Sometimes, it’s really obvious because you see a slice mark,” Zamora says.
Zamora’s monitoring at the Windy Flats project near Goldendale is part of a larger series of surveys to assess how the wind-power boom is impacting birds that must now share air space with the towering turbines.
The surveys, which are financed by the wind industry, indicate that wind power is a relatively minor hazard to birds. But some scientists say it is still too soon to discount the risks posed by the rush to develop Northwest wind power. They are particularly concerned with the plight of hawks, eagles and other raptors, which are large, longlived birds at the top of the food chain.
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One survey at Big Horn Wind Farm in Klickitat County estimated that more than 30 raptors were killed during an initial year of operations – more than seven times the number forecast in a pre-construction study. The dead raptors included kestrels , red-tailed hawks, shorteared owls and a ferruginous hawk, which Washington state lists as a threatened species.
“It’s just too early to say what this all means,” said K. Shawn Smallwood, a California ecologist who has published numerous scientific articles on wind farms and raptor deaths. “The science is just not there yet.”
There also is uncertainty about how raptors react to wind-power development, which often carves up foraging grounds with miles of new roads. Some say more studies are needed to determine if some species shy away from these areas or eventually abandon nests near the wind farms.
“Some of these projects are going up in undeveloped areas that were kind of havens for these species,” said James Watson, a Washington Department of Fish and Wildlife biologist who has spent 40 years studying raptors. “These turbines are occupying some of the flight space that is their bread and butter.”
Zamora works for West Inc., an ecological field-study company that has become a major contractor for the wind-power industry. The company’s surveys of turbine operations, which typically last a year or more, do miss some dead birds that get quickly picked apart by ravens, vultures or coyotes. Statisticians try to account for such removals in coming up with the final survey estimates that have been released for about a dozen Northwest wind farms.
Based on that information, the wind-power turbines currently operating in Oregon and Washington kill more than 6,500 birds and more than 3,000 bats annually.
In an era of climate change and a massive oil spill off the coast of Louisiana, windpower advocates say these deaths are an acceptable trade-off for development of a renewable energy source.
They note that house cats and other man-made hazards cause tens of millions of bird deaths each year.
Bird mortality “at wind farms, compared to other human-related causes of bird mortality, is biologically and statistically insignificant,” wrote Mike Sagrillo, a consultant who writes for American Wind Energy Association.
In recent years, some of the biggest Northwest concerns about raptors and windpower development have been in the plateau country of Klickitat County, whose farm fields and grazing lands offer a buffet of chukars, rabbits and other prey to birds that nest in the nearby Columbia River Gorge.
Wind-power developers, after consultations with state biologists, have agreed to relocate some turbines away from canyon edges frequented by raptors, and avoid installing them in some areas used by raptors or near their nets.
“We take the questions and concerns of wildlife impacts very seriously,” said Jan Johnson, a spokeswoman for Iberdrola Renewables.