BILLINGS, Mont. (AP) — The Trump administration moved forward Thursday with plans to ease restrictions on oil and gas drilling and other activities across millions of acres in the American West that were put in place to protect an imperiled bird species.

Land management documents released by the U.S. Interior Department show the administration intends to open more areas to leasing and allow waivers for drilling to encroach into the habitat of greater sage grouse.

Critics warned the changes could wipe out sage grouse colonies as drilling disrupts breeding grounds

Interior Deputy Secretary David Bernhardt said the agency was responding to requests by states to give them more flexibility in how public lands are managed. He said the goal to conserve declining grouse populations remained unchanged.

“I completely believe that these plans are leaning forward on the conservation of sage grouse,” Bernhardt told The Associated Press. “Do they do it in exactly the same way, no? We made some change in the plans and got rid of some things that are simply not necessary.”

The changes drew a sharp backlash from conservation groups and wildlife advocates, who warned they could push the birds onto the endangered species list.

“To have plans that took years of work, backed by good science and strong public support, brought into question is disheartening,” said Brian Rutledge, with the National Audubon society.

The ground-dwelling bird ranges across about 270,000 square miles (700,000 square kilometers) in parts of 11 Western U.S. states and two Canadian provinces. Its numbers have plummeted in recent decades.

Federal officials under President Barack Obama in 2015 adopted a sweeping set of land use restrictions intended to benefit grouse.

Under President Donald Trump, Interior Secretary Ryan Zinke has vowed to lift obstacles to drilling, and grouse protections have long been viewed by the energy industry as an obstacle to development.

Sage grouse are large, ground-dwelling birds known for an elaborate mating ritual in which males strut around breeding grounds with large, puffed-out air sacs protruding from their chests.

They once numbered in the millions. The U.S. Fish and Wildlife Service now estimates the population at 200,000 to 500,000. Energy development, disease and other causes have decimated populations in some areas.

The Trump administration’s proposal would reverse or modify the Obama-era protections in seven states — Wyoming, Nevada, Utah, Colorado, California, Idaho and Oregon.

Governors from several western states previously raised concerns over a related federal directive that would limit a type of land swap that can be used to preserve habitat for the birds.

Bernhardt said that in response, the Interior Department intends to align its practices with the policies in place in each state. If a state permit for activities on public lands requires conditions such as the consideration of land swaps, he said, corresponding federal permits would also include that as a condition.

Following Thursday’s release of environmental studies analyzing the changes in each state, governors and the public get another chance to weigh in before a final decision is expected in early 2019.