The 31-turbine Diablo Winds farm there, owned by Florida Power and Light, is equipped with larger, slower-spinning yet more efficient windmills designed to be more avian-friendly than the 169 smaller eggbeater-shaped turbines, turning at 72 rotations a minute, they replaced.

The brisk winds from the north Wednesday turned the 154-foot-in-diameter rotor slowly, at about 28 rotations per minute. But that still produces more than 600 kilowatts.

"Generally, the taller ones fare better with the raptors than the smaller turbines," said Steven Stengel, a spokesman for FPL.

Some of them standing at 164 feet, others towering at 181 feet, these larger machines are easier for birds to see, Stengel said. Also, the electric poles have been torn down and the electrical lines are all underground. Not long ago, eight miles of electrical lines ran through the area.

The new technology also allows workers to control these turbines from anywhere.

"We can monitor from our Livermore office, from Juneau Beach, Fla., or from a crew member's laptop," Stengel said.

Diablo Winds, which went online in 2004, is not one of the 29 farms whose operating permit approvals are being appealed to the Alameda County Board of Supervisors. But FPL has several hundred other turbines that could be affected by the supervisors' appeal decision, expected in June.

The repowering effort -- the replacement of old turbines and the renegotiation of contracts with landowners, PG&E and others -- should help cut deaths of golden eagles and other raptors, said Jeff Miller, spokesman for the Center for Biological Diversity. But it's not happening quickly enough, said Miller, who notes 880 to 1,300 golden eagles, owls, hawks and other raptors die in the Altamont each year.

"We want (companies) to commit to repowering the entire Altamont Pass" over the next five years, Miller said. His organization's goal is to reduce bird deaths by 50 percent within three years, and 85 percent within six years.

The California Energy Commission has made several recommendations on how to do that. They include removing lethal turbines or relocating them to areas where birds tend not to fly; ending a rodent-killing program and shutting down the wind turbines during the winter.

Companies are willing to comply with some, but not all, these suggestions. Operators prefer to shut down half the turbines for November and December and then in January and February shut down the remaining half.

Miller's organization is one of the environmental groups that have appealed the Altamont wind turbine permits, contending more thorough environmental study is needed.

The Center for Biological Diversity also has sued several wind energy companies, seeking restitution for the past killing of raptors. An Alameda County judge ruled this week the lawsuit cannot seek damages for the past bird killings, but can seek mitigation for future raptor deaths, Miller said.