Western Sprawl Is Gobbling Up Grassland Habitat, Raising Risks for Short-eared Owls

On an overcast day in early April, a group of amateur birders gathered beside a dirt road. Splinters of evening sun slipped through the cloud cover, casting a golden glow over the hay and alfalfa spread before them.

Their leader, 84-year-old Larry Weeks, swept his spotting scope back and forth across the horizon, looking like a landlocked pirate stranded in the agricultural landscape of western Montana. But the treasure Weeks was after wasn’t buried underground. He was searching for Short-eared Owls.

Every March and April, Short-eared Owls take to the skies to perform an intricate courtship ritual. The males launch themselves from the ground, flapping up to 1,000 feet in the air before plummeting in a series of drunken spins and dips. As they tumble toward the ground, the owls clap their wings in front of their breasts and hoot continuously.  

The display is spectacular, but it is also becoming harder and harder to observe. Since 1970, North America’s Short-eared Owl population has decreased by an estimated 65 percent, largely due to the degradation of grassland habitat. Found around much of the world, the birds are seasonally widespread in North and South America. But western states like Montana are especially important to the future of Short-ears, since many of them rely in all seasons on grassland and shrubland habitats from Washington to the Dakotas.

As a longtime birder and board member of Five Valleys Audubon, Weeks has organized these trips to see Short-ear mating flights for years. Today, however, he worries that the annual tradition may soon prove futile.

“Look at all the habitat here people are taking away,” Weeks said earlier in the day as he drove the group of birders north, out of Missoula. He gestured out the window to a newly constructed subdivision.

“Yeah, this wasn’t here five years ago,” another birder said from the backseat. “It’s coming in real fast.”

Between 2020 and 2022, Montana was the second-fastest growing state in the nation, surpassed only by Idaho. While the majority of its landscape is still rural, increased development has pushed wildlife into closer contact with humans.

The ground-nesting Short-eared Owl needs wide-open spaces, such as the prairies and sagebrush that stretch across much of the American West. Today, that means that many Short-ears live in pastures and croplands, which mimic the vegetation of their natural habitat. The grains often grown and used for feed on farms also attract rodents that the owls can eat.

The unfortunate trade-off for a quick meal and a place to nest is a plethora of human-imposed dangers. The birds tangle themselves in barbed wire fences, ingest rodenticides and pesticides, and get pummeled by cars tearing down rural roads. Some fall into stock tanks and drown when they are unable to fly back out with waterlogged feathers. Others are sucked into combines at harvest time. “Agriculture is boosting the prey population, but it puts them in proximity of greater risk,” says Robert Miller, a research biologist at Intermountain Bird Observatory.

Miller has led several projects tracking trends in Short-ear populations across the West, including the Western Asio flammeus Landscape Study—which uses the bird’s scientific name—otherwise known as Project WAfLS.

From 2014 to 2020, more than 1,200 volunteers conducted annual population surveys for Short-eared Owls at 436 survey sites across Washington, Oregon, Montana, Idaho, Utah, Nevada, California, and Wyoming. During the owls’ mating season, volunteers traveled between observation points, stopping at each area for five minutes to record the number of Short-ears they saw or heard.

As Short-eared Owls are nomadic and often don’t return to the same nesting sites, Project WAfLS provided a valuable baseline for how the birds are faring. Miller has observed low population years in Idaho corresponding with higher populations in Montana, suggesting that the West’s resident owls move within the region based on weather and food availability. By coordinating surveys across states, the effort provided a clearer understanding of the overall status of western Short-ears.

Drawing from these surveys, Project WafLS was able to observe patterns in populations and project how changes to western landscapes will affect Short-eared Owls. The short answer: negatively.

In a 2020 report, Project WAfLS estimated that the extinction risk for western Short-eared Owls will increase by 59 percent over the next 50 years. Miller said that this estimate was likely much too low, as the team calculated the effects of climate change using recommendations for emissions reductions in the Paris Climate Agreement. The United States has yet to meet these standards.

The greatest risk continues to be habitat degradation. Over the next 50 years, Project WafLS estimated that, in the eight-state study area, 76 percent of grassland habitat classified as “good” for Short-eared Owls would disappear due to climatic changes or development.

Montana is just one of many western states facing immense development pressures. Several other states where Short-ears live year-round—Utah, Nevada, Idaho, and North Dakota—have consistently topped population growth charts since the 1940s. “Grassland habitats are threatened in general, all across the country,” says Lauren Smith, the director of communications for the Owl Research Institute (ORI), a Project WAfLS contributor that has conducted long-term owl studies in Montana’s Mission Valley since 1988.

Now, ORI is looking for ways to convert the data gathered in Project WAfLS to real-world solutions. Smith says the group is starting to work with landowners throughout the Mission Valley to educate landowners on conservation techniques.

Miller, too, has turned his attention to solutions. In 2021, he announced Project ROAM (Reducing Owl Agricultural Mortality), which aims to reduce Short-eared Owl mortality with thermal imaging technology. Before farmers harvest their alfalfa crop in summer, scientists fly a drone over the field, looking for a heat signature denoting a Short-eared Owl. The farmers are then able to steer their combines around owl nests, preventing deadly collisions.

Other research projects and nonprofits are attaching flags to barbed-wire fences to deter owl collisions and installing “ladders” to help owls and other wildlife crawl out of stock tanks.

While such ventures may seem like band-aids over the broken bones of habitat fragmentation and climate change, Miller is hopeful they will add up to healthy owl populations. “It’s really the death by a thousand cuts kind of thing,” Miller says.

This spring, at least, Montana’s Short-eared Owls appeared to have a successful mating season. As the sun melted behind distant mountain peaks, Larry Weeks parked his car in a gap between two fence posts, facing an empty pasture. “This is the sweet spot,” he said.

On cue, two owls burst from the pasture, flapping their wings furiously to rise higher against the gray clouds. The birders scrambled for their binoculars and cameras and trained their lenses on the distant silhouettes. Without warning, one of the Short-ears dove out of formation, sweeping back upwards before it hit the ground. A few moments later, the other followed suit, embellishing its own dive with a series of seemingly sporadic twirls and swoops.

Within five minutes, both birds had disappeared into the grass. Soon after, the group piled back into their cars and wove their way through burgeoning twilight towards the highway, already recounting the owls’ display and promising to meet up again next year.