Bald Eagles and magpies feast on a deer carcass at a camera-trap station in Montana's Bitterroot Valley. Photo: Bitterroot Valley Winter Eagle Project

Conservation

Montana Landowners Are Hooked on Luring Eagles with Deer Carcasses

Carrion is key to studying the abundance of Bald and Golden Eagles—and a bevy of other wildlife—overwintering in the Bitterroot Valley.

The eagles seem to be taunting us. We’ve been hiding inside a ramshackle century-old carriage house in Montana’s Bitterroot Valley since dawn on a frigid January morning. In the two hours that have passed, five Bald Eagles have settled in the barren branches of nearby cottonwoods. I’m jonesing for the thermos of coffee I foolishly left in the car, and photographer Celia Talbot Tobin has to pee. Barb Garten, whose property we’re on, is waiting in her house across the field, ready to zip over when the coast is clear. No one can leave or enter this makeshift bird blind for risk of scaring off the raptors, which we’re trying to catch as part of a multi-year project on the Bald and Golden Eagles that overwinter in this narrow sliver of the Rocky Mountains.

The bait is a sliced-open deer carcass staked to the ground 20 yards from us, and tall grasses to one side camouflage a remote-controlled net. Dozens of Black-billed Magpies diligently tear at the whitetail’s frozen remains, but the eagles are wary. Finally, one drops down, 10 yards from the carcass.

Adrenaline washes away my grogginess. Talbot Tobin forgets about her bladder. Even Rob Domenech, who runs Montana-based Raptor View Research Institute (RVRI) and has trapped hundreds of eagles, is flooded with nervous excitement. “My heart rate is going up,” he says, sitting down to stop himself from pacing in front of the tiny windows and possibly spooking the bird. RVRI’s Mary Scofield has assumed a meditative mien: legs spread slightly, hands loosely holding the net-launcher remote, eyes fixed on the carcass, breath steady. Her colleague Brian Busby softly narrates the bird’s movements. “Here it comes, it’s taking a couple of steps,” he whispers. “It’s looking around . . . Oh—it hopped back a few feet.”

We watch as the Bald Eagle stalks forward comically, wings hunched up like a corny Dracula impersonator, only to retreat with a hop-flight. Thirty excruciating minutes tick by. The portable heater runs out of propane. “They don’t get to be an adult by being stupid and careless,” says Domenech. Though, he adds, Golden Eagles are less cautious. “Sometimes you’ll be focused on a Baldie doing this slow approach, and you’ll look over at the carcass and see that a Golden dropped out of the sky and is on top of it.” All heads swivel to the carrion. Nope. Only magpies.

Finally, the wary scavenger alights on the exposed rib cage. A few beats later there’s a loud “Pop!” as Scofield fires the net launcher. She and Busby burst out of the building. I emerge 30 seconds later, confused to see them each holding a magpie. The eagle, they say, slipped out under the net. They release the indignant-looking corvids they’d caught instead, then repack the net. It was a rare miss. From December through March the team trapped and banded 24 eagles, and affixed satellite transmitters to six adult Goldens—the species of graver conservation concern. 

As just a few hours spent in the field makes clear, tagging takes a lot of effort, plus some luck—and the team can trap only a fraction of the raptors that roam this narrow valley. So the Bitterroot Winter Eagle Project has devised a creative way to log each and every visitor lured by the roadkill bait: Build a volunteer army. This winter, about 30 tracts of private property hosted carcass stations, each equipped with a motion-detecting camera. Through the community science site zooniverse.org, thousands of people across the globe are helping classify the species captured in hundreds of thousands of wildlife-triggered photos; while eagles are the primary focus, the pictures reveal the wide array of creatures crossing these lands, including wolves and coyotes, lynx and mountain lions. It’s only the second year of the project, a collaboration between RVRI, Bitterroot Audubon Society, the research institute MPG Ranch, and 200 private landowners, but people near and far are hooked.

Garten, the landowner, spends several hours a day watching and photographing the eagles the carcass attracts, and eagerly awaits the latest camera-trap pictures the project coordinator shares with her. One day, she tells me, a Golden and eight Bald Eagles dined together. A bobcat once camped out on a carcass for days, deterring the eagles. And just three days earlier, Domenech’s team had captured two Baldies here, and Garten had helped tag a 14-pound raptor. “It’s been a thrill. How many people get to hold an eagle?” she says. “It’s so cool to see these mighty birds right here, to look out my window and watch them. And to know that we’re helping to make sure they stay healthy and mighty.”

Rob Domenech, director of the Raptor View Research Institute, collects discharged netting after an unsuccessful attempt to capture a Bald Eagle. Photo: Celia Talbot Tobin

D rive along Highway 93 tracing the floor of the Bitterroot Valley, in winter, and chances are you won’t see a single eagle; you’ll see loads of them. They perch like sentinels in roadside trees. They soar over ridges, titans that seemingly possess the power to fly without flapping their wings. This 95-mile-long stretch nestled between the Bitterroot Range and Sapphire Mountains attracts dozens upon dozens of eagles. Baldies fish in the Bitterroot River, and both species pick off rodents, jackrabbits, and gamebirds that abound in the region’s sprawling agricultural fields. And, of course, they scavenge roadkill—an especially enticing option when rivers are iced over and hard snowpack inhibits hunting.

Seeing the birds is one thing; understanding how they use the landscape, figuring out how many return each winter, and assessing their health requires a coordinated effort. That information is especially of interest when it comes to Golden Eagles, says Kate Stone, an MPG Ranch Biologist who started the project. 

Bald Eagles have made a remarkable comeback, rebounding in the Lower 48 to more than 70,000 individuals from fewer than 420 breeding pairs in the early 1960s. While widespread use of DDT, which contaminated fish and thinned eggshells, brought the birds to the brink, the pesticide didn’t hit Goldens nearly as hard, likely due to their preference for mammalian prey. But in the West, where three-fourths of the nation’s estimated 40,000 Golden Eagles reside, the birds seem to have declined, and the bird is listed as a “species of concern” in Montana. Counts at hawkwatch surveys indicate around a one-third drop in numbers in the past quarter century. The Bitterroot project is helping to identify possible contributors to the declines, where the birds head come spring, and critical habitat here in winter—information that’s more important than ever, says Stone, given the fast-expanding human population in the valley.

From the start, Stone knew private property owners would be essential to the project. “Eagles rely heavily on private lands in winter,” Stone says. “So collecting data on private land is really important.” 

Throughout the winter, Stone and her MPG Ranch colleague Eric Rasmussen visit the stations regularly to restock carrion, replace camera batteries, and download photos. Eagles and other wildlife pick a carcass clean in mere days. The project went through 132 deer this year alone. Most of the remains came from the Montana Department of Transportation, which would otherwise compost the animals; Stone, Rasmussen, and the RVRI employees also have permits to pick up roadkill. 

As for the potentially questionable practice of providing meals for wildlife, Stone points out that they only run the project in winter, when bears are hibernating. And it’s the time of year when eagles would typically feed on roadside carrion and gut piles discarded by hunters. “They’d be eating it anyway,” she says.

Except, maybe, in the case of the horse. When a neighbor’s mare slipped on the ice and broke its neck this winter, the owner donated it to the project. Stone installed the 1,000-pound beast at the carcass station by her house. It quickly drew crowds, avian and human. Thirty eagles descended on it at once—a spectacle that her Amish neighbors pulled up in their buggies to watch. “The school bus even stopped,” she says.

Across the valley, says Stone, people have come to feel a sort of ownership of the eagles.

 

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tone promised to introduce me to one of these proud locals, Barbara Lanoue, that evening, at a public event about the project in Stevensville, one of the towns in the valley. “She missed a doctor’s appointment today because she was so engrossed with ‘her’ eagles,” Stone tells me.

“I didn’t miss it,” Lanoue corrects me, when I ask her about the appointment. “But I was late.”

Michelle Falivene, another landowner with a carcass station, is set to jet off to Hawaii in a few days. But she’s tempted to cancel her vacation. “They just brought a fresh carcass to our property,” she says. “I wonder, what am I going to miss?” Multiple eagles might feast at once. A mountain lion or wolf might stop by and nibble in the night, caught in the act by the motion-detection camera. 

At a gathering at a bar in Stevensville, Montana, Kyle Barber pulls up the people-powered research platform Zooniverse as part of a demonstration to show volunteers how to navigate the website and tag the wildlife they identify in photos. Photo: Celia Talbot Tobin

Roughly a quarter of the 30 people who have gathered at the Stevi Cafe have carcass stations on their property. A handful, including members of Bitterroot Audubon, have brought laptops so they can log onto Zooniverse and process photos while sipping beers from Montana breweries with fellow volunteers.

Stone leads newbies through a demo projected on a flat-screen TV, while Zooniverse volunteer Kyle Barber navigates the site on a computer. He selects a photo, and Stone walks the crowd through an identification: six magpies and a Golden Eagle. The raptor’s face is hidden, but you can tell it’s not a juvenile, she says, and that it is a Baldie because its legs are entirely feathered. Stone also stresses that people should note if an eagle has leg bands and the color—which indicate where it was banded—or if it’s sporting a wing tag or satellite transmitter. That information helps track which birds are returning to the valley each winter and where they hail from.

In 2018, nine eagles were re-sighted. The camera traps spied five marked Balds: three adults banded in the Bitterroot, a juvenile banded on California’s Santa Catalina Island, and an adult banded in 2008 outside Flagstaff, Arizona. Of the four Goldens caught on camera, one had been banded by the U.S. Geological Survey, and the other three were from the Bitterroot project—two boasting satellite transmitters, and another with a wing tag.

Seven user’s IDs have to match in order for a photo to be deemed processed. Thankfully, online participation extends far beyond this passionate, but small, crowd: More than 4,300 volunteers worldwide have processed about 40,000 images, and identified more than 410,000 animals. “We couldn’t do this without the volunteers,” Stone says. “If we had to do all of the analysis ourselves, it would be prohibitive. There’s just no way we’d get it done.” 

Stone chalks up the impressive number of volunteers to people’s fascination with the magnificent raptors. “Everyone has an eagle story,” she says.

She’s using that shared interest to start a conversation in the Bitterroot and surrounding areas about one of the main threats to overwintering eagles: lead poisoning. Of the 171 Golden and Bald Eagles RVRI has trapped in the valley since 2011, 87 percent had elevated levels of the heavy metal, a neurotoxin that’s deadly at high concentrations. They primarily ingest lead from bullet fragments in gut piles left by hunters. It’s clear that the birds are being exposed to the toxin locally, says Domenech, since it’s only detectable in blood for two weeks. (Eventually it makes its way into bone.) “Our community outreach efforts focus on how using copper ammunition can lessen lead exposure,” Stone says. “We’re not trying to stop anyone from hunting.”  

“We grew up here, our families hunt, and we never knew about the lead until this project,” says Lanoue, who owns the Stevi Cafe with her husband. They aren’t alone; multiple people milling about had also only learned about lead poisoning in eagles through the project, and a couple of hunters noted that they were switching their ammo. It’s not a political thing, and a couple of people bristled at the notion of being called conservationists. “Everyone is here,” Lanoue says, “because of the eagles.” 

RVRI staff are able to trap only a fraction of the birds caught on camera; they aim to snare unmarked adults, all of which receive leg bands and either a satellite transmitter or a softball-size numbered wing tag. “We never instrument eagles that have been wing-tagged,” says Rob Domenech. “We feel it is simply too much paraphernalia to saddle a bird with.” Photo: Celia Talbot Tobin

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he day after the near-miss at the carriage house, the team captures a Golden Eagle at another site. Once the bird is deftly removed from the net, a hood is placed over its eyes to keep it calm, and someone always holds it securely. Unthinkingly, I reach out and touch its sharp talons, which are longer than my fingers, but it doesn’t flinch. The bird is outfitted with leg bands and a blue wing tag that proclaims it #361. Morphological measurements, including tail length and body weight—9 pounds—indicate that it’s likely a male. And a portable lead testing kit reveals that the concentration of the neurotoxin in this raptor’s blood is 55 µg/dL, far above the safe limit of 10 µg/dL.

Once the measurements and tests are done, Domenech forces several pieces of raw meat warmed in water into the bird’s crop, blasé about putting his fingers in the powerful beak. “We want to send him off with a full meal, so we don’t cause him additional stress,” he says. When Domenech tosses the raptor into the air, it flaps furiously, briefly touches down, and then disappears over a hill.

A Bald Eagle trapped at a carcass station on MPG Ranch is released. Video: Raptor View Research Institute

The eagles that overwinter in the Bitterroot Valley are just settling into their breeding grounds now. Nobody knows where birds with wing tags, like #361, have landed. But the paths of those with satellite transmitters has been mapped down to the foot. Demetrious, a male Golden Eagle the RVRI team captured this year, opted to stay close, taking up residence in a forested area about 10 miles east of Missoula, Montana. Judy, a female fitted with a satellite transmitter in January 2017, retraced the journey she made last spring, covering some 1,750 miles in three weeks to arrive in wilderness south of Anchorage, Alaska. Whether they migrated just a few miles or a thousand, the eagles will go about the serious business of breeding, rearing, and fledgling chicks. 

Come late fall, when the eagles take to the wing and head back to the Bitterroot Valley, humans won’t factor into their decision. But plenty of people, from landowners ready for the revival of carcass stations to Zooniverse volunteers curious to see what another winter brings, will be anxiously awaiting their return.

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