A recent study in Klickitat County, Washington shows that active wind farms in Washington and Oregon kill more than 6,500 birds and 3,000 bats annually. 

Biologist Orah Zamora works for West, Inc., an ecological field study company, monitors the Windy Flats project, one of the largest wind farms in the United States. Zamora looks for dead birds and bats that have been severed by the spinning blades of the surrounding wind turbines in order to conduct survey's to observe how wind-power development is affecting birds. 

"It's like a crime scene, and you try to figure out what happened," said Zamora. "Sometimes it's really obvious because you can see a slice mark."

These surveys are financed by the wind industry and are mainly concerned with birds like eagles, hawks, and other raptors. Klickitat County is especially a concern because the area has an abundance of prey for these larger birds, hence, they tend to stay in the area. According to the study, these birds are diving for their prey and do not pay attention to the large wind turbine blades that may be in the way.

There are differing views between scientists, biologists and wind-energy developers as to whether birds are at high risk because no one knows what cumulative death toll will have a significant impact on the species. 

Wind-power advocates say "these deaths are an acceptable trade-off for development of a renewable energy source." They also note that man-made hazards and house cats account for tens of millions of bird-related deaths per year. According to Mike Sagrillo, a consultant who writes for the American Wind Energy Association, bird mortality "at wind farms, compared to other human-related causes of bird mortality, is biologically and statistically insignificant."

The surveys taken in Klickitat County showed that wind power is only a minor hazard to birds, but scientists say it's too early to really "discount the risks posed by the rush to develop Northwest wind power."

A survey in Klickitat County at the Big Horn Wind Farm indicated 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." Among the dead birds were short-eared owls, kestrels, red-tailed hawks and a ferruginous hawk. 

"We take questions and concerns of wildlife impacts very seriously," said Jan Johnson, a spokeswoman for Iberdrola Renewables, which owns the Big Horn Wind Farm. 

In addition to these findings, Altamount Pass Wind Farms in California have older wind turbines from the 1980's that have killed more raptors "per megawatt of power than anywhere else in the nation." These wind farms kill more than 1,600 raptors per year.

While developers have agreed to relocate turbines away from canyon ridges where the large birds of prey spend most of their time, the death toll is still expected to rise due to the lack of information regarding what death toll is biologically significant to these birds. 

A study by West, Inc. that was paid for by the Klickitat County Planning Department showed that the turbines would kill 516 raptors each year just in the Columbia River plateau region of Oregon and Washington if the industry doubled in size. The study determined that this was not a significant number, but ecologist K. Shawn Smallwood thinks the study underestimates the number of deaths and that it's hard to conclude whether these wind turbine-related deaths would harm an entire species.