PORTLAND, Ore. (AP) -- Wind energy may be emerging as an important alternative power source for the Northwest, but there are concerns about the danger to hawks and eagles as turbines expand to wild areas of the Columbia River Gorge.

By year's end, more than 1,500 turbines will be churning out electricity in the windy gorge. Until now, most of the projects have gone up in wheat fields — cultivated land that long ago drove away the rodents that raptors hunt. But as wind energy developers move into wilder areas along the ridge of the gorge, near canyons and shrub-covered rangeland, birds could be at risk from the 150-foot blades of giant turbines.
The shrub steppes and grasslands that cover large areas along the river east of the Cascades are classic raptor habitat, said David Anderson, a district biologist with the Washington Department of Fish and Wildlife.
""We have concerns we're losing that habitat,"" he said.
Even the cultivated areas with wind farms have bird experts worried. In Oregon's Sherman County, several hundred turbines stretch through wheat fields outside the small town of Wasco, creating one of the highest concentrations of wind farms in the gorge.
""They're going up so fast, we're worried about the cumulative effects,"" said Keith Kohl, a wildlife biologist for the Oregon Department of Fish and Wildlife's mid-Columbia district.
If new studies confirm the fears of Oregon and Washington state wildlife biologists, the potential toll on raptors and other birds may limit expansion of clean wind energy.
Nationwide, wind turbines kill an average of 2.3 birds a year, studies show. In the Northwest, it's about 1.9 birds per turbine — possibly more than 3,000 bird deaths a year in the gorge.
But bird experts say those numbers are meaningless because the totals make no distinction between abundant and rare species.
Golden eagles and ferruginous hawks — a threatened species in Washington — already are few in number, said Michael Denny of the Blue Mountain Audubon Society. Even a few fatalities could prove devastating, he said.
""We'll have certain species in sharp local decline,"" Denny said. ""If you lose breeding populations like the ferruginous hawk, you're not going to see them recover.""
Raptors generally fly 300 to 400 feet above the ground — about the height of most wind turbines. Hawks and eagles ride the thermals off the high windy ridges above the Columbia River as they search for ground squirrels and pocket gophers. Some are migratory and others are resident birds.
Raptors are known for their keen eyesight and might learn to negotiate the turbines and their spinning blades, studies suggest.
But hunting and migrating instincts are so ingrained and so intense that the birds might not see the obstacles until it's too late, biologists say.
As a preventive measure, energy companies conduct wildlife studies before designating a specific site for development. They submit their findings to state or county authorities, who decide whether projects will go forward.
In some cases, regulators have required developers to shift turbine locations, establish buffer zones or set aside acreage exclusively for wildlife.
Often, developers must patrol their wind farms and record bird kills.
""We pride ourselves on building projects that adhere to the requirements,"" said Darin Huseby, Northwest regional director for developer enXco Inc., a California-based company with several projects in Klickitat County, Wash. ""We want to be a net benefit to the environment.""
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