An estimated 1,200 bats, most of them probably just passing through Montana, were killed after striking wind turbines at the Judith Gap Wind Farm between July 2006 and May 2007, according to a post-construction bird and bat survey.
The number surprised Invenergy, which owns the farm, as well as government and private wildlife experts.
“It’s killing 1,200 bats a year and that’s a lot more than anybody anticipated,” said Janet Ellis of Montana Audubon, a bird conservation group.
TRC Solutions of Laramie, Wyo., completed the survey work on behalf of Chicago-based Invenergy.
Frank Pizzileo, Invenergy’s director of wind-asset management, said the study concluded this spring and is currently being finalized.
An estimated 1,206 bats, or 13.4 bats for each of the 90 turbines, were killed as they flew through the wind farm between July 2006 and May 2007, the study states.
The turbines are 262-feet tall with blades that sweep 253 feet in diameter.
The study estimates that 406 birds, or 4.52 birds per turbine, were killed during the study period.
The bird fatality rates are similar to those at other wind plants in the United States, the study states. But the estimated number of bat fatalities was higher than those reported at other wind farms in the Western United States, according to the study.
“It does seem to be a bit of a bat highway,” said Allison Puchniak Begley, a Montana Fish, Wildlife & Parks native species biologist in Billings.
Ellis and Puchniak Begley serve on a technical advisory committee that Invenergy agreed to form to help monitor bird and bat mortalities after the facility opened in January 2006.
Judith Gap’s turbines spread across 8,300 acres of private and state school trust land 125 miles southeast of Great Falls between the towns of Judith Gap and Harlowton.
For the study, bird and bat carcasses were collected monthly at survey plots at 20 of the wind farm’s 90 turbines from August to October in 2006 and February to May in 2007. Carcasses that were found incidentally – outside of the official searches – also were included as part of the study.
A total of 62 carcasses were found – 36 bats and 26 birds.
The casualty estimates of 1,200 bats and 400 birds were calculated using a mathematical formula based on the sampling.
“We just don’t know enough about bats in Montana, migration corridors or anything,” Ellis said.
Wind farms in the Eastern United States have reported higher bat fatality rates than Judith Gap, but those wind farms were located on mountain ridge tops where migrating bats presumably were concentrated, the study states. The Judith Gap facility is on the plains.
Bats show an unexplained tendency to collide with the blades of wind turbines in some locations of the country, said Mark Wilson, field supervisor for the U.S. Fish and Wildlife Service, adding there are 16 species of bats in Montana, including six that are “species of special concern,” which means they are uncommon and need monitoring.
The hoary bat, a species that can have a wingspan of up to 16 inches, was the most common species killed, with 17 carcasses found in the study. Four of the dead animals were silver-haired bats. Another 14 bats couldn’t be identified.
Both the hoary and silver-haired bats live in the forests of southern Canada and migrate through Montana in the late summer on their way to warmer climes.
“They are big pest-control species that eat their body weight in bugs every night,” Ellis said.
The new information from the Judith Gap Wind Farm could be of help to developers in siting future wind farms, Puchniak Begley said.
“It’s green energy, but it can be greener when it’s better sited,” she said.
Not much research has been done on bats in Montana, so there’s little information available about their migration pathways, said Kristi Dubois, native species coordinator for FWP and the head of the Montana Bat Working Group.
With wind development on the rise, the impact of the turbines on bats is a major concern of biologists, she said.
Despite the bat fatality numbers, Judith Gap is a well-sited wind farm because it is close to roads and cropland and doesn’t break up a lot of native land, Puchniak Begly said.
It’s possible the effect on bats could be mitigated with some simple adjustments, she added.
For example, studies at wind farms in the Eastern United States showed that a large number were killed on nights when it wasn’t very windy. She suggested starting some turbines at Judith Gap only after wind speeds pick up.
Invenergy’s Pizzileo said the number of bats killed was higher than the environmental assessment completed before construction projected. The company is working with the technical advisory committee, state and federal wildlife regulators and conservation groups to determine what steps to take next.
“These next steps will be publicly available soon,” he said.
Ellis said she is pleased the company is willing to work with the committee.
“They don’t have to do that,” she said.
The study comes as developers are prospecting for wind and planning wind facilities in a wind-rich zone between Great Falls and the Canadian border along the proposed Montana Alberta Tie Line transmission line route that would connect the electrical grids in the Electric City and Lethbridge, Alberta.
“We are concerned with possible significant bat mortality from wind power projects that are connected to the MATL transmission line,” Wilson wrote in a letter to Anthony Como, the U.S. Department of Energy’s director of permitting and siting.
Wilson’s comments were part of the Fish and Wildlife Service’s official comments on the MATL line to the DOE and the state Department of Environmental Quality, which are jointly preparing an environmental impact statement on the project.
A draft EIS conservatively estimated that 400 to 533 wind turbines could be constructed along the proposed line.
The Fish and Wildlife Service is encouraging wind farm developers to complete preconstruction bat monitoring using acoustic and radar detectors, in addition to post-construction monitoring.
“There’s no getting around it, (turbines) do kill birds and they do kill bats,” said Kevin Van Koughnett of Calgary-based TransAlta Wind, which has wind farms 250 miles north of Great Falls in Pincher Creek, Alberta.
However, he said it is important to keep the deaths in context. Far more birds and bats are killed by buildings and cars than by wind turbines, he said. The rule of thumb in the industry is that for every bird killed by a turbine, thousands more are killed in other ways, Van Koughnett said.
He added that his company is cooperating with bat research being conducted by the University of Calgary.
By Karl Puckett
Tribune Staff Writer
20 July 2008
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