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When wildlife biologist Carl Brown bailed out of his pickup at 11,000 feet one July day, high in the Beartooth Mountains of northwestern Wyoming's Rockies, I hardly recognized him. He wore a helmet and carried an ice ax strapped to his backpack. Crampons, cams, hexes, carabineers, ropes tied in Prusik knots, slings, and other climbing gear dangled around his narrow torso. As he walked toward me, he rattled. I had to look hard to find his binoculars.

Tall and well-tanned, Brown was first introduced to me by a coworker as “130 pounds of twisted steel and sex appeal.” I can vouch for his cable-like strength and endurance. We walked to a sea of sharp-edged boulders the size of pianos above a huge drop-off. Brown, 31 at the time, led the way across them, floating boulder tip to boulder tip laden with gear, while I scrambled behind on a pair of 63-year-old knees. When I finally caught up to him, he was knotting a rope.

Brown had chosen the site for its high elevation and north-facing cliffs surrounded by tundra and heavy snowpack. We stood there looking down over the edge at a verdant, lake-strewn valley showing not a human blemish, separated from us by a sheer granite verticality of well over 300 feet.

“This,” Brown told me as he peered over the chasm, “looks like a good place for finches.” He fastened his rope and his life to a large boulder and dropped over the snow cornice and out of sight.

On that summer day in 2015, Brown was just stretching his legs and climbing ropes. A practiced climber and seasonal biologist with the Wyoming Game and Fish Department, he was preparing to embark on a master’s program at the University of Wyoming. He would be investigating what is ­arguably the least-known, least-studied bird species in North America, the Black Rosy-Finch.

Like Brown, the Black Rosy-Finch—BLRF in birders’ shorthand—has a penchant for the highest, most precipitous terrain. About the size of a large sparrow, the Black Rosy-Finch nests in Wyoming and a few nearby states at 10,000 to 14,000 feet, in the crevices between rocks in near-vertical cliffs. Very few biologists have managed to follow them to these heights. Researchers have conducted significant studies less than once per decade since 1925, when the first nests were recorded. Between then and 2002, the year of the in Birds of North America, three researchers had documented only 23 nests. No one had studied the species in Wyoming since the 1950s.       

This would be Brown’s decade, and his work only gains urgency with each passing year. Wyoming biologists consider these finches to be among the highest-altitude vertebrates reproducing in the state. And high altitudes, like high latitudes, are some of the locations where animals experience the effects of ����APP change first and most harshly. As temperatures rise, there will eventually be no farther habitat to migrate to, neither above the mountaintops nor toward the North Pole—the main reason why Brown calls this bird “the polar bear of Wyoming.”

For the Black Rosy-Finch, survival will hinge on how quickly ����APP change affects its alpine nesting grounds. Any shift in snow melt or tundra habitat could impair the bird’s ability to find food and raise its young. Unless scientists understand where it nests and whether its population is dwindling, we could miss not only the passage of a species but also the first red flag for how warming will impair the region’s high-mountain habitats and the wildlife that depends on them. What Brown set out to do is finally offer a way to track rosy-finch numbers.

From somewhere below the rim Brown hollered up. He was seeing Black Rosy-Finches, he said, and I could, too. He had told me earlier: Look for the flash of pink and the mylar-brilliant wing linings aglow above the snow. And there they were, several winging low over the piano boulders with woodpecker-like shallow swoops, then diving into the abyss. I began to hear the quiet chew, chew, chew he had played for me on his iPhone.

Hours later Brown’s rope began to sizzle in the crusty cornice-edge snow. When he reappeared, he held up two fingers. Peace? Victory? No, Brown had found his first two nests, one from a previous year, and a new one with four chortling chicks. They were tucked into adjacent crevices so narrow that a human hand would barely fit: shallow bowls four to five inches across, woven of moss and grasses and lined with the hair of mountain goats.

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pon arriving on their breeding grounds in spring, Black Rosy-Finches seek out melting snow. They stick close to its interface with recently exposed open tundra, foraging on the moist border that attracts insects and supplies newly uncovered seed heads from the past year. Later, in the summer fledgling period, finches harvest fresh seeds from the dry tundra and pluck insects blown by updrafts onto the remaining snowfields. Research shows that insects are so important to the birds’ diet that trout stocked in high-country lakes near rosy-finch strongholds may significantly reduce their food intake.

Susan Patla, a nongame biologist recently retired from the Wyoming Game and Fish Department, says the best estimates suggest a range-wide population of only some 20,000 Black Rosy-Finches. Annual show a slight downward drift in numbers, although that may not reflect true population trends. Those surveys offer just snapshots of the birds in winter, when their movements are nomadic and they mix with flocks of other species of rosy-finches, often near bird feeders. No one knows exactly where the Wyoming nesting population goes in winter, says Patla, but both she and Brown agree that this lower-altitude habitat, even if it shrinks, won’t be the life-or-death factor.

It’s the breeders that count—up high and in the summer. That’s the habitat most in danger, and there’s no one up there to feed them. Warming temperatures reduce snow cover and cause snow to melt faster and earlier, depriving the finches of the chance to feed on the snow-tundra edge when they most need to. Warming also allows shrubs to creep upward insidiously, overtaking the tundra’s grasses and forbs that provide seeds. This succession is already apparent in high-altitude studies in Colorado. As the treeline moves upward, rosy-finch range contracts and eventually disappears.

Patla remembers when Brown began showing up at her office after hours with scientific papers on rosy-finches. He was drawn to study the birds precisely because so few others could. “As a Wyoming climber and wildlife biologist, I felt obligated,” he told me. Plus, the prospect of discovering the secrets of a little-known species in a landscape he loved to explore was irresistible.

And so Patla pushed for funding to establish a baseline survey. Wyoming’s State Wildlife Action Plan the Black Rosy-Finch as a Species of Greatest Conservation Need, which put the bird in the top tier of the state’s list of priorities. And she knew all too well, from the agency’s experience with the lynx, what happens without better monitoring: “We assumed [the population] was secure, but by the early ‘90s it was virtually gone.”

Eventually Brown met Anna Chalfoun, a U.S. Geological Survey research ecologist and University of Wyoming scientist, who secured added funding for him to join her lab. Chalfoun, a songbird-habitat specialist, became Brown’s thesis adviser. “Carl, with his mountaineering and keen observation skills, was the man for the job,” she told me.

Brown’s study had two objectives. First, he’d assess the abundance of Black Rosy-Finches across their varying alpine habitats, determine the foraging areas they require, and use that data to predict their distribution across Wyoming. Then he would develop protocols for conducting the first accurate long-term monitoring of the species in the state. This would lay the groundwork for tracking the population in Wyoming and could be useful across its breeding range. Brown says wildlife officials in Montana are already interested in the techniques.

The work could also improve monitoring for the Black Rosy-Finch’s close relatives—the Brown-capped Rosy-Finch, which nests mainly in Colorado, and the Gray-crowned Rosy-Finch, which nests largely in western Canada and Alaska. The , all high-altitude breeders that prefer rocky crags and tundra, are so similar that in the 1980s, scientists briefly considered them a single species (along with a fourth in Asia). Ultimately, if studies of any of these species point to significant declines, that could trigger federal or state protections for one or more of their populations.

The problem is that reaching that point could take many years or even decades, and conservationists don’t know if they have that much time. “The most alarming part,” Brown says, “is the speed at which the change of habitat is quietly advancing.”

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n August 2017 I met up with Brown again, this time with his two field assistants. We camped once more in the Beartooths, where Brown had found his first two nests. Over this and the previous summer, Brown and his technicians had covered four mountain ranges each year, three times each over the breeding season. They split up in the early morning hours to walk transects a little longer than a mile, accumulating copious data from more than 170 routes.

Before light we were up, coffeed, and off. I followed Brown over high, rolling tundra—half stony, half soggy to start, far from a verticality and therefore also from any finches. In the distance, grandiose outcrops of pink and orange granite boulders rose beneath a set of tall cliffs—Black Rosy-Finch country for sure. Brown had his ice ax lashed to the back of his pack, business-end down, with his helmet looped over the handle, in case a flurry of finches on the nearby cliff inspired a nest search. A clipboard hung from a cord around his neck; compass, inclinometer, laser rangefinder, and GPS swung from his belt.

Brown walked in silence, pausing to raise binoculars every few steps. Upon spotting a bird, he’d check his instruments and scribble on a data sheet. He recorded every species on the ground, in flight, or even only heard. Every few yards, he’d stop and look around 180 degrees—the slow, alert dance of a field biologist. At the top of a steep canyon, he scrambled down over granite rubble. A bird flew across while he was looking for footing—he didn’t miss it.

After a day of surveying, Brown went over the cliff on a rope in the late afternoon and came back in the gloaming: The birds nested again this year, in the same crevice as in 2015. Brown was ecstatic—it was his second observation of Black Rosy-Finches returning to the same nests, which he noted had rarely (if ever) been documented before. The next day he and his assistants walked more transects, and Brown came back with news of a new late nest with nestlings still in it. “They looked like five peeps in the end of an egg carton,” he said.

The results of all this work so far are substantial. Brown identified 15 Wyoming nests, raising the count nationwide from 23 to 38. In 2015 alone, he documented breeding Black Rosy-Finches in seven mountain ranges, three previously unreported, extending the species’ breeding range in Wyoming significantly southwest of its known distribution. And although he and a statistician are still crunching data for Brown’s thesis, several trends are already evident from his and his team’s surveys.

Perhaps of greatest importance is where most Black Rosy-Finches occur in the breeding season. Most have been observed within about 650 feet of cliffs on tundra exposed by a receding snowfield before the birds nest; at cliff-side while they’re nesting; and in a variety of places—on dry and moist tundra and snowfields—when the young have fledged. This is the grit from Brown’s data that will allow close monitoring; if populations decline—and they will if rising temperatures continue—it will signal major damage to a functioning alpine ecosystem.

In reality, the bird’s numbers may already be declining in places, much like the pika, a tiny mammal that breeds in high montane slopes of scree and talus, overlapping with parts of finch nesting range. Habitat changes that affect the Black Rosy-Finch may also eventually challenge other high-nesting birds, such as montane populations of American Pipits.

In the meantime, Brown’s decade continues. In 2018 he visited seven mountain ranges on his own. This year he’ll continue his survey over fresh terrain. And even as he moves on to other projects, he plans to continue keeping track of the birds. As he said, “If you enjoy something and you have the skill set and the opportunity, why wouldn’t you?”

On our final morning together, Brown finds me near the drop-off where he started, in a boulder-strewn mosaic of tundra and hard rock. He has just walked his last transect below the cliff—not a finch to be seen. But up here, dozens of Black Rosy-Finches flit about, feeding fledglings and splashing in the meltwater. Brown is in his element. Though the habitat is in flux, here in the morning sunlight, life on the edge remains robust and beautiful among the pink granite boulders whose color is timelessly mirrored in the feathers on the flanks of finches.

This story originally ran in the Summer 2019 issue as “A Slippery Slope for a Mountain Bird.” To receive our print magazine, become a member by .