A wildlife protection fight over a quirky ground-dwelling bird highlights how two U.S. environmental groups have increasingly dominated the process of species protection, sparking a backlash from pro-business Republicans.

A Reuters review of hundreds of federal records over a 10-year period shows how the non-profit groups have had success by inundating Washington with petitions for new protected-species listings and lawsuits designed to compel regulators to respond.

Many of the new listings achieved by the Center for Biological Diversity (CBD) and WildEarth Guardians have been for relatively obscure species, such as snails and fish with compact habitats.

But their effort to protect a wide-ranging bird called greater sage grouse has now sparked a backlash from critics who say the Endangered Species Act is being manipulated and abused by environmentalists through aggressive legal actions and closed-door settlements.

The federal government must decide by Sept. 30 whether to protect the sage grouse - which roams wind-swept grasslands spanning 11 Western U.S. states - under the 1973 law.

Though its habitat is vast, the number of grouse, known for their elaborate mating dance, had fallen to between 200,000 and 500,000 by 2010 from the millions historically, and its territory has shrunk due to development, according to the government.

As the listing deadline nears, it is becoming the focus of an effort in the Republican-controlled U.S. Congress to roll back the Endangered Species Act.

Republican lawmakers such as Congressman Rob Bishop, head of the House Natural Resources Committee, and Senator James Inhofe, chairman of the Senate environment committee, are seeking to overhaul the law by giving more power to states and increasing the transparency of legal settlements and listing decisions.

Political foes of listing the sage grouse for protection have sought to block it with legislation in recent months.

Bishop attached a measure to a defense spending bill that passed the House earlier this year that would prohibit any listing of the sage grouse for 10 years. It's unclear whether the amendment will make it into the final law.

"The Endangered Species Act has gone from a well-intentioned piece of legislation in the 1970s to one that is dictated by environmental activist groups taking advantage of the adversarial system," Inhofe said at a hearing on the act in May.

Oil and agricultural interests want the West's arid expanse of sagebrush - one of the last great undeveloped wildernesses in the United States - kept open for drilling and grazing.

The stakes are high because the sage grouse's range is so vast, covering 165 million acres - a little under the size of Texas. For critics of the grouse's listing, mostly businesses and Republicans, putting a regulatory fence around the grasslands to protect the bird would represent the height of "big-government" overreach.

Lawsuit strategy

The U.S. Fish and Wildlife Service (FWS), which administers the law, had sought to delay a decision on the bird, but cases brought by the two environmental groups have forced the issue.

Under the Endangered Species Act, the government can list species on its own, or members of the public, or groups can make the case to add a species to the list by filing a petition.

The two groups have exploited bottlenecks in the species-listing process by flooding the government with petitions. When a deadline for a listing decision is missed, they have used litigation to enforce them. Other groups petition and sue the government over species, but none have been quite as prolific as the CBD and WildEarth.

Faced with more than a dozen lawsuits, the FWS entered into historic settlements with the two groups in 2011 requiring the government to make decisions on hundreds of species. In return, the groups agreed to limit deadline lawsuits for several years.

The sage grouse was included in the settlement after the CBD and WildEarth sued to challenge the government's 2010 ruling that the bird warranted protection but that other species were a higher priority.

Of the more than 600 species now under FWS review, about 77 percent were submitted by the CBD. Another 16 percent were petitioned by WildEarth. Many of these species were part of a 2010 "mega-petition" from the CBD that included 404 species, as well as two huge 2007 petitions from WildEarth to list nearly 700 species.

The FWS, whose listing budget shrank to $20.5 million for fiscal 2015 from about $22 million in 2010, has often been unable to meet the law's strict deadlines because it was overwhelmed by the amount of new petitions and lawsuits, agency officials say.

Overwhelming the government

More than 70 percent of FWS species listings since 2004 were spurred by lawsuits, with the majority of them filed by the CBD and WildEarth, based on a review of government data.

"The only way to get the agency's attention was to have a massive number of petitions that kind of overwhelmed the agency and forced them through a little shock therapy," said WildEarth Executive Director John Horning.

From 2005 through 2009, the FWS listed at least 24 species for federal protection after being sued by outside groups.

Between 2010 and 2014, when the two groups' strategies took full effect and after President Barack Obama took office, that jumped to at least 197 new listings due to lawsuits.

Overall, listings climbed from just seven species in 2008 to a high of 89 species in 2013, before falling to 38 in 2014.

Both founded in the Southwest in 1989, the CBD and WildEarth seek protection for all threatened species, including obscure creatures like crayfish, beetles, and mollusks.

In 2014, WildEarth reported it had an income of about $3.6 million, with grants serving as the largest source of income. Major contributors during that period included Patagonia, an outdoor clothing company, and Wilburforce Foundation, a private charity that funds conservation in the western United States and Canada, according to the group's annual report.

The CBD brought in about $9.3 million in 2013, mostly from membership fees and donations, according to its latest annual report online. Major donors reported by the CBD that year include Fred Stanback, an heir to the Stanback headache-powder fortune, and Andrew Sabin, a metals magnate and conservationist.

Noah Greenwald, endangered species director for the CBD, told Reuters the legal actions were necessary.

"Species don't make campaign contributions and there are going to be political forces opposed to species conservation," Greenwald said. The lawsuits "balance that out," he said.

Although the FWS argues that the 2011 settlements brought order and predictability to the listing process, Republican lawmakers say the agreements were reached without serious input from the states or Congress.

The Interior Department in May issued plans to conserve sage grouse habitat in 10 states. Opponents of listing the sage grouse hope these plans, along with state efforts to protect the bird, will convince the service a federal listing is unneeded.

Further lawsuits are expected no matter what the government decides on the grouse.

Retired Democratic Representative John Dingell, who co-authored the Endangered Species Act, said the flood of litigation surrounding the law does not reflect the original intent of Congress. He said the lawsuits could be prevented if sufficient funds were provided to implement the law.

"The intent of the Congress ... is being significantly perverted, both by the polluters and the people who want something done," Dingell said.