LOS ANGELES (Reuters) - The number of breeding males in the greater sage-grouse population of the United States and part of Canada has declined by 56 percent in recent years, in a sign of trouble for the ground-dwelling bird, a study released on Friday showed.
The study from the Pew Charitable Trusts comes as the U.S. Fish and Wildlife Service prepares to make a decision before the end of September on whether the bird should be protected under the Endangered Species Act.
U.S. Secretary of the Interior Sally Jewell announced on that a sub-species of the sage-grouse found in California and Nevada did not require protection under the Endangered Species Act. Environmentalists criticized the decision.
The move was a victory for mining, energy and farming companies which fear sage-grouse protections could restrict their livelihoods in the 11 Western states where the bird lives, including Washington state, Colorado and Montana.
Millions of sage-grouse are believed to have once inhabited a broad expanse of the Western United States and Canada. The U.S. Fish and Wildlife Service estimated in 2010 that between 200,000 and 500,000 birds remain.
The Pew Charitable Trusts study did not give a complete estimate of the total number of sage-grouse birds that might live in their range in the 11 U.S. states and a southern portion of the Canadian province of Alberta.
But the study said just 48,641 breeding males were found in 2013, representing a 56 percent decline from 2007 when the count was 109,990.
Edward Garton, the lead researcher on the study, said sage-grouse populations typically fluctuate greatly, decreasing and then rebounding as a natural phenomenon.
“Is it part of the typical cycle, or are the populations actually collapsing? We don’t really know the answer to that,” Garton said.
There might have been about 125,000 breeding birds in total in 2013 including females, Garton said.
If the sage-grouse population is falling due to environmental degradation, the chief culprits would be oil and gas development and the increasing prevalence of wildfires, he said.
Projecting 100 years into the future, most sub-populations of the sage-grouse would reach numbers so low they would risk dying off from genetic defects, Garton said.
The Fish and Wildlife Service said it valued the latest study.
“The Garton study is one of several population trend analyses that will help us assess the health of the greater sage-grouse and inform our status review of the species,” it said.
Reporting by Alex Dobuzinskis in Los Angeles; Editing by Sandra Maler