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In Wyoming, the debate over sage grouse centers in large part around oil and gas development. Drillers often occupy the same space as the bird, leading to concerns that oil and gas fields will contribute to a wider loss in grouse habitat. 

But the sage grouse is a far flung species -- its range spans 11 western states -- and the challenges it faces in different regions vary. In some areas, the spread of invasive species like cheatgrass are leading to a loss of sage brush. In others, urbanization is responsible. Often times, multiple factors are at play.  

Range wide, the long-term population trend is clear: Sage grouse numbers are down significantly over the last half century. Yet regional variations exist. 

Two recent studies broke down how sage grouse are faring in different regions across the West. One, by prominent sage grouse researcher Edward Garton, a professor at the University of Idaho, recorded a 56 percent decline in male grouse across 10 states between 2007 and 2013. Another, by the Western Association of Fish and Wildlife Agencies, reported male sage grouse counts have rebounded 63 percent in the last two years. 

Their methods vary slightly. Garton largely presents his findings in terms of total birds counted. WAFWA records its count in terms of the number of males recorded per lek. 

Both studies will be among the research considered by the U.S. Fish and Wildlife Service as it prepares to make a decision over the bird's future.

The service is under a court-ordered deadline to announce whether the bird warrants protection under the Endangered Species Act by Oct. 1.

What follows is regional overview of the various challenges facing sage grouse across its range. The threats spelled out below were identified in a 2012 report by a team of federal and state scientists. Each region is broken out into management zones established by the Fish and Wildlife Service. 

One last caveat. Sage grouse populations naturally fluctuate, creating peaks and valleys over the years. Scientists often compare historic peaks to present ones and historic valleys to current ones as a way to discern an overall population trend. 

And with that, away we go... 

Management Zone 1 - The Great Plains

Location: Eastern Montana, western North Dakota, western South Dakota and northeastern Wyoming

Threat: The conversion of native sage brush to cropland poises the primary threat to grouse across much of northeastern Montana and the Dakotas.  Energy development is the chief source of habitat loss in Wyoming's Powder River Basin. It also presents a danger in the Bakken. 

Population trends: The Great Plains account for roughly 10 to 15 percent of the bird's population, depending on what study you use. 

But both the Garton and WAFWA studies agree on this much: Sage grouse in the Great Plains are severely challenged.   

WAFWA found the number of male grouse per lek declined by a rate of 2.7 percent annually since 1965. The group called the decline "concerning," noting the rate of decrease appears to have accelerated in recent years. 

Garton, meanwhile, reported sage grouse in the Powder River Basin are teetering on the edge of the "extinction vortex." Across the Great Plains, the number of male sage grouse decreased by 67 percent between 2007 and 2013, settling at 6,674 males.  

Management Zone II - Wyoming Basin

Location: West-Central Wyoming, and parts of northern Colorado and Utah.   

Threat: Energy development is the primary threat, though new housing and infrastructure also present challenges. 

Population: The Wyoming Basin is home to the greatest percentage of sage grouse across the West, accounting for almost half of the bird's population. 

Garton and WAWFA come to dramatically different conclusions about population trends in the region.

WAFWA found the average male lek count in Wyoming alone has increased by .3 percent annually since 1965, though that figure might be artificially high due to a biased 2006 count. Also encouraging: A low in males per lek recorded between 2006 and 2013 was higher than lows recorded in 1995 and 1996. 

Garton reports the number of male grouse declined 63 percent between 2007 and 2013 to around 20,600 birds.  

Management Zone III - Southern Great Basin

Location: Utah, central Nevada and a limited portion of eastern California. 

Threat: Encroaching conifers and the expansion of cheatgrass are two of biggest dangers, although infrastructure and urbanization also poise substantial challenges.  

Population: The Southern Great Basin accounts for roughly 10 percent of the bird's populations.  

WAFWA concluded grouse populations in the region have stablilized and may even be increasing slightly. Average males per lek increased by an average annual rate of .19 percent between 1965 and 2015. 

Garton recorded a 34 percent decline between 2007 and 2013, when 5,485 birds were counted. 

Management Zone IV - Snake River Plain

Location: Idaho, southwestern Montana and parts of northern Nevada and Utah. 

Threat: Invasive species like cheatgrass are the main worry here, though conifer encroachment, urbanization and infrastructure projects also rank on the list of concerns. 

Population: The Snake River Plain is second only to the Wyoming Basin in terms of grouse population. Estimates vary from 23 to 30 percent of the bird's total population.  

Garton found the number of male birds fell from 19,510 in 2007 to 13,371 in 2013, a decline of 32 percent. WAFWA found an average annual rate of decrease of .7 percent, but noted recent population lows were similar to what was recorded in the past.  

Management Zone V - Northern Great Basin

Location: Northwest Nevada, southwest Oregon and parts of northeast California

Threat: Much like the Snake River Plain, the Northern Great Basin is confronted with the expansion of cheat grass. Conifer encroachment, urbanization and infrastructure are also threats. 

Population: About 5 percent of the total population. Both studies conclude grouse are declining in the Northern Great Basin. WAFWA found an average annual rate of decline at lek sites of 1.38 percent. Garton reported a 65 percent drop to 2,573 birds in 2013. 

Management Zone VI - Columbia Basin

Location: Washington

Threat: Conversion of sage brush for cropland is the top threat. Invasive species also poise a challenge. 

Population: The Columbia Basin accounts for a small fraction of the bird's population. Garton recorded 291 birds in 2013 out of roughly 44,000; WAFWA counted 366 this year, compared to 80,000 rangewide. Both studies recorded a slight decline in the bird's numbers in the Columbia Basin. 

Management Zone VII - The Colorado Plateau 

Location: Colorado and part of eastern Utah

Threat: Infrastructure, energy development and urbanization are the chief challenges. 

Population: The Colorado Plateau is the least populated region in the sage grouse's range. It accounted for just 241 birds in Garton's study. He did not estimate a percent change. WAFWA combined the region with the Wyoming Basin in its study. 

Follow energy reporter Benjamin Storrow on Twitter @bstorrow


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