BILLINGS, Mont.—A California utility that wants to back out of a northwest Montana wind power project is asking a federal judge to decide if the wind farm's developers did enough to protect a nearby cluster of golden eagles.

San Diego Gas & Electric claims in court documents that a U.S. subsidiary of Spanish wind power company NaturEner misrepresented the risk of the birds being harmed by the Rim Rock wind farm near Cut Bank.

In court documents filed over the last two weeks, the utility has sought to withdraw its pledge to invest $285 million in the $400 million project. It also wants to cancel a 20-year contract under which it was buying renewable energy credits from NaturEner.

But NaturEner says SDG&E is using the eagle issue simply as a pretext for getting out of contract it no longer finds favorable. The company alleges the utility is suffering from "buyer's remorse" as the cost of renewable energy has fallen from when the two struck their deal almost two years ago.

The 126-turbine project is in an area that has seven golden eagle nests and is home to dozens of other raptors, including Montana's densest concentration of ferruginous hawks, according to Montana Audubon.

NaturEner USA spokesman Patrick Ferguson said Thursday that the company has gone to great lengths to protect the eagles, and none has been hurt since the turbines began operating last year. The company uses radar and workers on-site to watch out for eagles and other large birds, and can shut down its turbines if a collision is pending.

NaturEner earlier moved 25 of its towers farther away from nesting areas after complaints from Montana Audubon and others that the project was in the wrong place. Under an agreement signed with the conservation group, the company also said it would continue work to reduce impacts to bird and bat populations.

The two sides filed lawsuits against one another in state courts in California and Montana last week.

SDG&E on Monday sought to move the case to U.S. District Court in Montana, saying that because eagles are a federally protected species the matter should be handled by a federal judge.

Montana Audobon program director Janet Ellis credited NaturEner for taking extra steps to protect eagles and other birds. But she added that for much of the past year only some of Rim Rock's turbines were operating because it had not yet been hooked up to a new transmission line.

"NaturEner is doing quite a bit, but it's really premature to see if what they put in place is working" she said.

NaturEner wants the case sent back to state court in Toole County. The wind power company is seeking a restraining order from District Judge Robert Olson to block SDG&E from canceling its contracts Jan. 1.

The request for a restraining order was filed under seal, which Ferguson said was done to protect proprietary information.

To secure the loan used to construct Rim Rock, NaturEner put up as collateral almost all of its assets—including its two other Montana wind farms. If SDG&E has its way, Ferguson says his company would be unable to repay the loan. He warned that all three wind farms could be foreclosed upon.

"We're one of the largest taxpayers in Toole and Glacier counties," he said. "All of those things are on the line."