ELKINS, W.Va. -- Lights left on at a power substation on a foggy night during the fall migration season are believed to be responsible for the deaths of nearly 500 songbirds earlier this month at the new AES Laurel Mountain wind farm near Elkins.

"From a bird conservation perspective, it was a very bad event," said Kelly Fuller, wind campaign coordinator for the American Bird Conservancy, a national bird conservation group headquartered in The Plains, Va.

More than half of the birds involved in the incident were blackpoll warblers, with Connecticut warblers, yellow-billed cuckoos, sora and Virginia rail among other species reportedly found dead near the substation

The bird kill occurred Oct. 2-3, according to Division of Natural Resources spokesman Hoy Murphy

The bird kill did not apparently involve collisions with wind turbines at the 61-tower complex, according to a preliminary investigation. Instead, the deaths reportedly occurred from "a combination of collisions with the substation and exhaustion, as birds caught in the light's glare circled in mass confusion," according to a release from Fuller's organization.

The incident occurred during a period of fog and poor visibility.

Night-migrating songbirds flying in such conditions without a horizon to follow, or without recognizable patterns of light to indicate the sky above, or dark to indicate the ground below, can become "trapped" by steady burning lights. In such cases, the area below them appears lighter, due to the lights, while the sky above appears darker, reversing the birds' sense of up and down. Birds can circle such lights long enough to die of exhaustion or collide with a structure.

Murphy said AES is drafting a final report on the incident, which will be submitted to the DNR and the U.S. Fish and Wildlife Service. Further comment from the DNR was not expected until after that report is reviewed.

Fuller said the Laurel Mountain bird kill was the third involving migrating birds, fog, and lights being left on overnight at West Virginia wind farms.

On Sept. 24 at NedPower's Mount Storm wind farm, 59 birds and 2 bats were killed. Thirty of the birds were found dead in the vicinity of a single wind turbine that was reported to have internal lighting left on overnight.

On May 23, 2003, 30 birds were killed at Mountaineer Wind Energy Center on Backbone Mountain in Tucker County, after lights were left on at a substation during a foggy night.

The three wind farms with the bird kills operate at night, while West Virginia's fourth operational wind farm, Beech Ridge Wind Energy in Greenbrier County, is prohibited by court order from operating at night between April 1 and Nov. 15.  Beech Ridge has not experienced large bird mortality events, Fuller said.

"Wind energy has the potential to be a green energy source, but the industry still needs to embrace simple, bird-smart principles that would dramatically reduce incidents across the country, such as those that have occurred in West Virginia," Fuller said.

"The good news is that it shouldn't be hard to make changes that will keep these sorts of unnecessary deaths from happening again, but it's disturbing that they happened at all," she said.

"It has long been known that many birds navigate by the stars at night, that they normally fly lower during bad weather conditions, and that artificial light can draw them off course and lead to fatal collision events. That's why minimizing outdoor lighting at wind facilities is a well-known operating standard."

Fuller said the bird kills reinforce the need for "mandatory federal operational standards, as opposed to the optional, voluntary guidelines that are currently under discussion."

According to the American Bird Conservancy, the West Virginia bird kill numbers fly in the face of industry assertions that wind turbines kill, on average, two birds per year.

"Some West Virginia conservation groups have suggested that other wind farms in the state should shut down their turbines at certain times and seasons to protect birds," Fuller said. "Given the recurring bird kill problems, that idea needs to be seriously considered, at least during migration season on nights when low visibility is predicted. A wind farm in Texas is doing just that, so it is possible."

Reach Rick Steelhammer at rsteelham...@wvgazette.com or 304-348-5169.