The US Fish and Wildlife Service, part of the Department of the Interior, also is developing voluntary procedures for wind projects, a spokeswoman said.

Wind power, which is expected to increase by 26 percent in power generating capacity this year, is mostly unregulated in the United States except by county boards, city councils and local planning commissions.

Wind energy accounts for less than 1 percent of the nation's electricity supply -- enough power to serve 3 million households.

A study issued by the National Academy of Sciences in May said the percentage of birds and bats killed by collisions with wind towers and spinning turbine blades was small compared with kills from vehicles and buildings.

No one knows the actual number of birds killed by wind turbines, but estimates range from 30,000 to 60,000 a year, according to the American Bird Conservancy.

The wildlife group, in testimony to Congress in May, estimated that adding more wind power over the next 20 years to help meet a goal of 20 percent renewable energy supplies by 2030 could kill 900,000 to 1.8 million birds a year.

The California measures aim to help wind developers site and build emissions-free energy while protecting wildlife, said Julia Levin, global warming climate change director for the National Audubon Society.

"Without guidelines, controversies and conflicts between wind developers and wildlife groups will only get worse and slow down projects and make it harder to get financing," Levin said in an interview.

FEDERAL & STATE LAWS

The California steps tell counties and cities what is needed to comply with the state's Environmental Quality Act and how to meet other laws, including state and federal wildlife measures, the federal Migratory Bird Treaty Act, and endangered species laws.

The California Energy Commission and the state's Department of Fish and Game began work on the guidelines after the CEC published a report on bird deaths at one of the biggest wind farms in the nation.

The study estimated that as many as 4,700 birds from 40 different species, including 1,300 protected raptors, were killed annually by turbine blades at the Altamont Pass wind center about 50 miles (80 km) east of San Francisco.

Altamont Pass is along a Pacific Coast migratory path for raptors and near a nesting area for golden eagles, hawks, falcons and owls.

The yearly death toll included more than 100 golden eagles plus red-tailed hawks, burrowing owls, kestrels and meadowlarks, according to the Audubon Society.

FPL Energy, the largest US wind energy company, and other developers at Altamont Pass are working to cut bird deaths in half by 2009 and joining with the Audubon Society and local government to come up with a long-term environmental protection plan, said Elizabeth Murdock, executive director of Golden Gate Audubon.

The plan's key efforts are "repowering" Altamont Pass with fewer but more efficient wind turbines with high blades that spin above the birds' flight paths, and shutting down part of the wind farm during winter.