BILLINGS, Mont. (AP) — A government report with significant implications for the U.S. energy industry says a struggling bird species needs a 3-mile buffer between its breeding grounds and oil and gas drilling, wind farms and solar projects.

The study comes as the Obama administration weighs new protections for the greater sage grouse. The ground-dwelling, chicken-sized birds range across 11 western states and two Canadian provinces.

A 3-mile buffer for the birds represents a much larger area than the no-occupancy zones where drilling and other activity is prohibited under some state and federal land management plans.

However, those plans also contain more nuanced provisions, which backers say will protect sage grouse, such as seasonal restrictions on drilling or other activity and limits on the number of oil and gas wells within key sage grouse habitat.

Some wildlife advocates say too much energy development is being allowed, undermining efforts to help grouse. Such opposition could be bolstered by Friday's U.S. Geological Survey report.

The USGS made no management recommendations, and agency scientists said the buffer distances were for guidance only.

Greater sage grouse populations dropped sharply in recent decades due to disease, pressure from the energy industry, wildfires and other factors.

Now state and federal officials are scrambling to come up with conservation measures to protect the grouse ahead of a court-ordered September 2015 decision on protections.

A related bird, the Gunnison sage grouse of Utah and Colorado, received federal protection as a threatened species on Nov. 12. An adviser for Colorado Gov. John Hickenlooper said Friday that the state plans to challenge the decision in court.

The USGS report on the more-common greater sage grouse represents a compilation of scientific studies aimed at seeing what it takes to protect the bird.

It was requested by the U.S. Department of Interior's Bureau of Land Management, which oversees millions of acres of sage grouse habitat and regulates the energy industry across much of the West.

BLM spokesman Jeff Krauss said the agency will use the new information as it works on changes to land use plans that include new sage grouse conservation measures.

The report said a minimum buffer extending to a 3.1-mile radius around sage grouse breeding sites would provide considerable protections for the bird. That radius would equal a circle around the leks covering 30 square miles.

The report suggests a maximum buffer of 5 miles.

By comparison, Montana and Wyoming have adopted management plans for the bird that call for a no-surface occupancy zone of six-tenths of a mile around breeding sites, or leks, in key sage grouse habitat. That's an area of slightly more than one square mile.

The state plans also limit human activity within a larger area around breeding and nesting seasons. And they take into account cumulative impacts, such as a restriction in Wyoming that limits oil companies to one well pad per square mile in key habitat. That keeps sage grouse habitat intact, Wyoming Petroleum Association Vice President Esther Wagner said.

"That reduces (habitat) fragmentation, which is what it all comes down to," Wagner said. "It's working here."

But Steve Holmer, a senior policy adviser for the American Bird Conservancy, said larger no occupancy areas around leks are needed if sage grouse populations are to survive.

"There really needs to be a hard and fast rule about no occupancy," he said. "When it comes to oil and gas, those have been found to immediately drive out leks if they're too close."

The U.S. Fish and Wildlife has determined that Wyoming's sage grouse plan — used as a template for Montana's — is protective of the bird, agency spokesman Theodore Stein said.

Krauss, the BLM spokesman, pointed out that the report offered a range of buffer distances. "There is no single number for an appropriate buffer distance for any particular type of disturbance," he said.

Land managers also need to take into consideration local conditions across the grouse's sprawling, 257,000-square-mile habitat, USGS senior science adviser Carol Schuler said. Friday's buffer recommendation was meant to offer a reference point as more localized decisions are made, she said.