CHEYENNE, Wyo. -- The U.S. Fish and Wildlife Service says it opposes construction of any wind farms in Wyoming's core sage grouse population areas, a position that wind developers say could have a chilling effect on their plans in the state.

Brian Kelly, supervisor in the agency's Wyoming field office, made the comments in a letter Tuesday responding to an inquiry from the Wyoming Game and Fish Department.

"Constructing wind farms in core areas, even for research purposes, prior to demonstrating it can be done with no impact to sage grouse, negates the usefulness of the core area concept as a conservation strategy and brings into question whether adequate regulatory mechanisms are in place to protect the species," Kelly said in the letter.

The chicken-sized bird is under federal review for consideration to be listed as threatened or endangered under the Endangered Species Act. Last month, the Fish and Wildlife Service said it had delayed any decision until a May 2010 deadline.

Wyoming Gov. Dave Freudenthal issued an executive order last August restricting development in critical sage grouse habitat, known as core population areas. A state task force developed the rules to try to prevent the federal government from listing the chicken-sized bird as an endangered or threatened species.

The Game and Fish Department is studying at least two projects in the state's core areas, which cover about 23 percent of Wyoming.

Those projects include a plan by Anschutz Corp. to build a $4- to $6-billion wind farm south of Rawlins on a mix of private, federal and state land. Game department biologists have said more than half of the project is in core sage grouse areas.

"We have to work our way through the process, and if this is going to be the guidelines in the process, we'll have to evaluate our project - everybody will have to evaluate their projects - to see if they remain viable," said Bill Miller, president of Power Company of Wyoming, an Anschutz Corp. affiliate.

The federal agency's position could also affect Horizon Wind Energy's proposal to build a 198-turbine wind farm near Medicine Bow in a core area. Horizon's project also includes an ongoing scientific study looking at how wind farms affect sage grouse.

There have been no conclusive study of wind turbines' affect on sage grouse, though several studies are under way.

"These core areas were developed with oil and gas maps, and wind wasn't at the table and we weren't invited, so wind was not incorporated in that policy from the beginning," said Nate Sandvig, Horizon's project manager for the Simpson Ridge project. "We knew (the bird) was there from the beginning, but the rules of the game have been changing back and forth. We all want to do the right thing, and we don't want to see this bird listed."

Aaron Clark, an adviser on energy infrastructure to Freudenthal, said the governor's office supports the Fish and Wildlife Service's hard line on wind farms in core areas.

"We don't want to close the door on everything for ever," Clark said. "If somebody can bring in some really good science that shows that wind turbines don't have an adverse effect on sage grouse, obviously then our position needs to change. But everything we've seen so far is pointing the exact opposite way."

The state's regulatory hook is the Wyoming Department of Environmental Quality's Industrial Siting Council, a seven-member governor-appointed council that reviews the socio-economic and environmental impacts of industrial projects.

The council has permitting authority over industrial projects with construction costs of $173 million or more, regardless of who owns the land.

Clark said Wyoming's goal is to avoid a federal listing for the bird. Federal protections could have a stultifying influence on oil and gas development, agriculture and other economic development.