Christian Hagen says bird experts had long believed that sage grouse stayed away from juniper trees.
But today they can cite long-term research rather than just the stories they swapped while bouncing along in pickup trucks on the tracks that pass for roads in much of the sage grouse’s habitat in Eastern Oregon’s sagebrush steppe.
“I’m tremendously excited to see this positive signal,” said Hagen, an avian ecologist at Oregon State University and co-author of a new study that shows sage grouse, a candidate for federal protection, prefer to nest in places free of junipers.
The U.S. Fish and Wildlife Service decided in 2015 to not list sage grouse as threatened or endangered, although environmental groups continue to advocate for its protection.
John Severson led the study as research for his dissertation at the University of Idaho. The study was published in the journal PLOS ONE, a peer-reviewed publication.
The research, done between 2010 and 2014 in Lake County, Oregon, and in California and Nevada near the Oregon border, strengthens the scientific case that removing juniper can make habitat more suitable for sage grouse, Hagen said.
Although the study was done in South-Central Oregon, Hagen said he’s confident that the findings are relevant throughout the sage grouse’s range, which in Oregon extends as far north as Baker County.
“There’s no reason to believe it’s not applicable to sage grouse anywhere there’s a (juniper) issue,” he said.
Hagen, Severson and the other researchers collected data from 219 female sage grouse and 225 of their nests, some in parts of Lake County where juniper trees were cut, and some in areas of California and Nevada where where juniper were present but were not cut. Both study areas included private and public lands.
Among the study’s findings:
• Annual survival among female sage grouse increased by 6.6 percent in the areas where juniper trees were cut
• The survival rate of chicks in nests increased by 18.8 percent each year in areas where junipers were removed
Hagen said the spread of juniper can harm sage grouse habitat in two main ways.
First, junipers, each of which, when mature, can suck up as much as 40 gallons of water per day, can suppress the growth of sagebrush, which grouse depend on for hiding cover and, during winter, for food.
Second, junipers serve as perches and as hiding cover for raptors and other birds that prey on sage grouse.
Biologists had long ago noticed that sage grouse tend to avoid areas where junipers grow, Hagen said — including areas that had ample supplies of sagebrush and all the other habitat elements that the birds need.
“We had pretty strong empirical evidence that birds were avoiding tree-encroached areas,” Hagen said. “This is the first rigorous test of that.”
The spread of junipers
Although the juniper is native to Oregon, biologists have for several decades tracked the trees’ expansion into areas east of the Cascades that were previously dominated by sagebrush, native bunchgrasses and other vegetation.
Hagen said the latest estimate is that junipers occupy about 9 million acres in Oregon where the trees were absent or rare just a century or so ago.
“The problem is quite large,” he said.
Biologists attribute the expansion of juniper to factors such as widespread overgrazing of cattle and sheep early in the 20th century that suppressed native vegetation, as well as aggressive firefighting that reduced the frequency of range fires that used to control the fire-prone junipers.
The detrimental effects of the juniper proliferation have not gone unnoticed, or unchallenged.
Cattle ranchers, including several in Baker County, have worked on their own and with financial and technical aid from local, state and federal agencies over the past decade or so to cut junipers on tens of thousands of acres.
These projects were designed to spur the growth of forage grass and to increase the amount of water available, but landowners and agency officials also understood that cutting junipers could benefit sage grouse.
In 2010, for instance, the U.S. Department of Agriculture allocated $16 million for juniper eradication in six Oregon counties: Baker, Crook, Deschutes, Harney, Lake and Malheur.
Most of that money went to Harney, Lake and Malheur counties, where the majority of Oregon’s sage grouse habitat is (Baker County has about 6 percent of the bird’s habitat in the state).
Two federal agencies, the BLM and the Natural Resources Conservation Service (NRCS), paid for Severson and Hagen’s research project.
Local rancher not surprised by study’s findings
Mark Bennett, who owns a cattle ranch near Unity in southern Baker County, has cut juniper on 7,000 acres of his ranch over the past decade with grants from the NRCS, Oregon Department of Fish and Wildlife and the Oregon Watershed Enhancement Board, as well as his own money.
He was pleased to read the sage grouse-juniper study.
“It’s nice to see an outside confirmation of what we’ve really believed is happening on the ground and what we have said all along is happening as landowners,” said Bennett, who’s also a Baker County commissioner. “It’s not a producers’ group that’s affirming the action. It’s a research university — a well-respected research university.”
Bennett said he has seen the benefits of cutting junipers on his property.
Sagebrush cover is increasing in those areas, he said, but predatory birds aren’t as common.
“We see raptors all the time. You just don’t see them perched out there where the sage grouse are,” he said.
Bennett said surveys by state and federal agencies have shown an increase in sage grouse numbers on his property.
Besides removing juniper, Bennett said he has used other tactics to protect sage grouse, such as installing markers on fences to help birds avoid flying into fences, and putting ramps in cattle water troughs that allow birds to escape troughs rather than drowning.
Hagen emphasized that the published study’s findings constitute only the preliminary stage of research he hopes will continue for many more years.
He is particularly interested in tracking sage grouse population trends for at least a decade following the removal of juniper, to see whether the gains continue.
Regardless, Hagen said the four-year study “adds a level of credibility” to the strategy of removing junipers to improve Oregon’s rangeland, whether the overriding goal is to benefit livestock grazing, native plants, water supplies or sage grouse habitat.
“We’re showing that you can conduct these treatments, even if for other reasons, and get all these benefits for the bird,” Hagen said.
Joshua Dillen of WesCom News Service contributed to this story.