By Matt Miller, senior science writer
Golden eagles are arguable the fiercest predator in the sky: after all, what other bird could take down full-grown wolves?
But the golden eagle may have met its match with a most-unlikely new adversary: a non-native weed.
That’s according to research conducted by HawkWatch International, as reported this week by Brett Prettyman in the Salt Lake Tribune. The raptor conservation group found a 50 percent decline in the study area in Utah’s West Desert, attributed to a growing presence of invasive cheatgrass.
Cheatgrass is a plant that causes many sleepless nights for Nature Conservancy ecologists and land stewards in the western United States. The spread of this Eurasian has well-publicized and devastating effects on such charismatic species as sage grouse and mule deer.
And now, it appears, golden eagles.
Aldo Leopold presciently warned that cheatgrass would come to dominate arid regions of the West. And as usual, he was right.
Cheatgrass has taken a hold in sagebrush country due in large part to its adaptation to fire. Sagebrush habitats are adapted to infrequent fire; some sagebrush ecosystems historically only burned every 75 years. When sagebrush and related native shrubs burn frequently, they cannot recover.
Cheatgrass, as an annual, is adapted to frequent fire. Here’s the formula for ecological disaster: A fire burns, and cheatgrass takes hold. Another fire burns, making way for more cheatgrass. And more, and more. Soon a once-diverse habitat with many native plants becomes a cheatgrass monoculture.
The many features provided by this habitat for animals like deer and grouse – diverse food sources, hiding cover, nesting areas – disappear.
In the case of golden eagles, cheatgrass eliminates habitat and food for its main prey animal, the jackrabbit. Lost the jackrabbit and you lose the eagle. A similar phenomenon has been recorded in Idaho at the Morley Nelson Snake River Birds of Prey National Conservation Area, home to the largest population of nesting raptors on earth. There, cheatgrass has led to a reduction in ground squirrel numbers, which those raptors eat.
Cheatgrass is present on at least 60 million acres in the western United States, making it a daunting problem for conservationists and land managers. Eradication is little more than a dream, but research efforts offer hope for getting the plant under control. Biocontrol using a fungus pathogen, currently being tested in Washington, shows a lot of promise when combined with other methods.
The most unusual cheatgrass control? NPR’s Science Friday revealed an effort to brew cheatgrass beer. While I’m not sure it will be a viable strategy, I’d love to think that quaffing a craft beer might help our Western arid lands – and give golden eagles and other native wildlife a boost.
Thanks, Matt, for sharing this project with your readers. Our scientists here at HawkWatch International have been gathering the data and running the analyses on this issue for more than three years now. During the various field seasons, our scientists witnessed up close the severe drops in jackrabbits and successful Golden Eagle nesting activity in the West Desert; but to see that 50% decline number written in black and white after all the analyses brings a whole new urgency to the issue. As a former Nature Conservancy staffer, I appreciate the work you’re all doing to better understand and manage the threat of cheatgrass.
[…] cheatgrass moves in, native animals move out. This story reports on a decline in golden eagles in Utah’s western desert because cheatgrass crowded out […]