Why Sage grouse don't like junipers

Why Sage grouse don't like junipers

David Sparks Ph.D.
David Sparks Ph.D.
New research finds sage grouse populations grow faster in areas with juniper tree removal.

Recently published research found sage grouse populations  grow faster in areas restored by removing juniper trees, highlighting a key to sage grouse conservation efforts in the West.

The research, culminating findings of an eight-year study in the Warner Mountains conducted by University of Idaho and Oregon State University students and advisors, found that strategically removing encroaching trees spells good news for sage grouse, a declining upland bird that serves as a key indicator for the overall health of the sagebrush biome.

This study adds to a growing body of research -- much of it based on the long-term study in the Warner Mountains -- that documents the numerous benefits of conifer removal for wildlife and grazing lands.

The Warner Mountains run north to south from southern Oregon into northern California. In Oregon’s Warner Mountains, sagebrush rolls across hillsides and valley bottoms, providing productive land for livestock and wildlife.

Like many places in the West, these valuable rangelands are at risk from encroaching trees that displace wildlife, reduce livestock forage, and decrease available water. More than one million acres of sagebrush grazing lands in the Great Basin have turned into pinyon-juniper forests in the past two decades alone.

Sage grouse, a bird who evolved in a large and treeless landscape, suffer when trees take over. Birds avoid mating or nesting if there are more than a couple trees on the landscape, likely because conifer woodlands are riskier habitats for grouse with more predators. Other sagebrush-reliant wildlife like mule deer and songbirds are also negatively impacted when conifers crowd out the perennial plants they need for food and cover.

“In places where junipers were removed, the sage grouse population grew at a rate that was 12 percent greater than in an area where no trees were cut,” explained Andrew Olsen, who led the research for Oregon State University. “By targeting removal where sagebrush plants were still intact, we bought instant habitat for a declining bird species.”

Unfortunately, trees are taking over America’s grazing lands at an alarming rate. Conifers like Western Juniper have expanded by as much as 600% over the last 150 years — and 90 percent of that expansion has occurred in sagebrush country.

Olsen’s research demonstrates how removing expanding conifers before they get too dense can bring back the birds. A previous study from the Warner Mountains found that 29% of marked hens moved back to nest in restored habitat just three years after conifers were cut. Additional research in the Warners also revealed the abundance of sagebrush-loving songbirds, also species adapted to large treeless expansions, doubled following restoration through juniper removal.

“While conifer removal in the Warners has been shown to help sage grouse, many different wildlife and plant species are also benefiting from the restoration of these open sagebrush habitats,” said Todd Forbes, district manager of the Bureau of Land Management’s Lakeview District in Oregon.

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