Portland, OR (AHN) - Wind turbines, used as an alternative source to generate electricity, kills an average of 2.3 birds a year, studies show. The number is rising in the Northwest, where it's about 1.9 birds per turbine, concerned scientists say.

By December 2007, more than 1,500 turbines will be churning out electricity in the Columbia River Gorge. Scientists are also concerned that since the turbines are nearing along the ridge of the gorge, canyons and shrub-covered rangeland, the natural habitats of the birds could be at risk.

David Anderson, a district biologist with the Washington Department of Fish and Wildlife told the AP, "We have concerns we're losing that habitat."

Wildlife biologists in Oregon and Washington state say the turbines are taking toll on raptors and other birds and it may limit expansion of clean wind energy.

Michael Denny of the Blue Mountain Audubon Society said, ""We'll have certain species in sharp local decline. If you lose breeding populations like the ferruginous hawk, you're not going to see them recover."

Golden eagles and ferruginous hawks are a threatened species in Washington and already few in number. Other threatened species include raptors, which generally fly 300 to 400 feet above the ground, about the height of most wind turbines.

According to AP reports, energy companies have begun to conduct wildlife studies as precautionary measures before designating a specific site for development. They now plan to submit their findings to state or county authorities, who will further decide on the fate of the project.

Some wild life regulators have also urged developers to shift turbine locations, establish buffer zones or set aside acreage exclusively for wildlife.