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On a brisk August morning in Tasermiut Fjord, southern Greenland, I poke my head from the hatch of my family’s 13-meter sailboat to find frost on the deck and a cloudless sky. It’s weather that demands exploring. After my husband and I haul our eight- and 10-year-old sons from bed and row the dinghy to the beach, we begin our trek up Klosterdalen, also known as Monastery Valley, where lichen-covered stone ruins of Viking-era structures rest among a jumble of talus.

Sacrificing dry feet to a tapestry of muddy sloughs and clear pools, we watch Arctic char flash their gunmetal backs while water beetles skim the surfaces. As we hike, I mark our route by the birds we see: rock ptarmigan sitting sentry on the tundra; snow buntings flashing distinctive white wing patches; flocks of redpolls thick with downy-headed juveniles. It’s the season of abundance in the North, the pregnant pause before autumn edges toward winter.

After lunch, my older son points out two mallard ducklings pressed against the shore, all but disappearing into the overhanging mud bank. A moment later, another bird swoops overhead, its shadow passing so close I can almost touch it with my outstretched hiking pole.

“Look!” my younger son whisper-shouts. “It’s a peregrine!” For a split second, beating wings blot out the sun.

And there it is: a Greenlandic peregrine falcon, a bird I’d sailed thousands of ocean kilometers to find. Against the crisp sky and crimson-tinged heather, lit by the low-angle afternoon light, the falcon’s sleek silhouette glows.

Unlike many of my other ventures as a field biologist searching for birds in far-flung locations, this isn’t a scientific assignment. Over the previous year, I’ve been sailing with my family from the Mediterranean to the Arctic, slowly connecting the dots between Greece and Greenland. Somewhere along the way, sparked by a passing comment from a colleague, I’d learned about a population of peregrines that call Greenland home. My initial curiosity soon evolved into a minor obsession, revealing as it did a tale of recovery, resilience, and change that transcends this small polar population.

Peregrine falcons hold near-mythical appeal in our collective imagination, and for good reason. Topping out at speeds of more than 320 kilometers an hour, they’re the fastest species on Earth, plummeting from the sky like amber-eyed missiles. They hit their prey at such staggeringly high velocities that they’ve prompted studies on the physics of momentum and the aerodynamics of flight. Their nest sites, or aeries—selected for their inaccessibility to predators and view of the world below—often require biologists to include technical climbing gear as part of their standard kit. As falconry subjects, they’ve inspired a vernacular of terms that roll off the tongue like a chant—tiercel, eyas, bewit, creance, stoop, keen, haggard, passager, bate. And with sharply masked faces, delicately barred undersides, and wings shaped like boomerangs, they’re also a visual delight.

As for the peregrine now cruising hip-high over the tundra in front of us, I couldn’t have Photoshopped a more stunning backdrop. August has ushered in the first hues of fall, with birch leaves yellowing and blueberries ripening on their stems. Ahead, hanging glaciers mark the terminal forks of the river; behind, the fjord is studded with icebergs. Towering above the red-gold valley is one of the world’s most formidable granite faces, casting a shadow that darkens the sea. For elite big-wall climbers, the peak is a coveted destination. For a falcon, it’s a hell of a place to call home.

Mesmerized, we watch the bird hunt: one moment as weightless as a feather in the breeze, the next slamming toward the ground in pursuit. For several minutes she continues this dance of floating and falling, hovering and stooping, giving form to the air like a master carver to wood. Then, presumably with a meal clenched in her talons, she turns abruptly toward her home cliff and disappears.

In the afterglow of our sighting, surrounded by the pulse of life that marks a late Arctic summer, it’s easy to envision the grandeur of this valley in perpetuity, and equally easy to ignore the signs of change, both visible and not. As a biologist, I’m keenly aware that we’re living in an age of extinction, but here, now, I couldn’t conjure a sense of absence if I tried. In fact, I’m hard-pressed to feel anything but awe. Like the researchers I’ll soon meet—a binocular-clad cult of falcon fanatics who chase their subjects to the far ends of the globe—I’ve inadvertently become a peregrine fangirl.

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Perhaps more cosmopolitan than any other wild bird species, peregrine falcons live on every continent except Antarctica, in habitats ranging from polar deserts to subtropical rainforests. They’re flexible in what they eat—from songbirds to seabirds, carrion to chickens—and in where they nest—on cliffs, in trees, on the ground, or on buildings. Some individuals barely budge throughout their lifetimes, whereas others, like the Greenlandic variety, embody the roots of their scientific name—Falco peregrinus, or “wandering falcon”—making migrations upwards of 25,000 kilometers per year.

Today, peregrine falcons are a familiar sight in many North American cities, earning them the reputation of being pigeon-eating, skyscraper-roosting urban dwellers. Some people see them as nuisance birds, with their raucous calls and fierce hunting habits, leaving streaks of white guano decorating city buildings and piles of bloodied feathers in backyard chicken coops. However, not so long ago, we flirted with the very real possibility of never seeing them again.

Over their long history, peregrines have been persecuted and revered with equal enthusiasm. The fossil record tracks the species to the mid-Pleistocene, while accounts of peregrines in human culture date back at least several thousand years. Before assuming their prominent role in modern falconry, they were mummified and placed in Egyptian tombs and proffered as gifts among royalty in ancient China. They feature in the art and legends of many Indigenous cultures and were sometimes depicted as winged messengers between earth and sky. They’ve also roosted solidly in our literary canon, from Greek mythology to Shakespeare to contemporary bestsellers. A peregrine graces the cover of the 1950s classic My Side of the Mountain, which I read aloud to my children on our passage to Greenland.

Popularity of a wild species doesn’t guarantee its longevity, however—a lesson that humans have learned many times over and still seem unable to fully grasp. Like other aerial predators, peregrines were deemed pests throughout much of the Western world in the 19th and 20th centuries and were routinely plucked from the sky by bird hunters, pigeon fanciers, and gamekeepers. During the Second World War, the falcons met an unlikely foe in the British Royal Navy, which killed them across Europe in order to protect homing pigeons delivering messages between military personnel. Yet the biggest insult of all came as industrial farming took hold around the world, introducing DDT, dieldrin, and other organochlorine pesticides.

Since birds like peregrines feed high on the food chain, contaminants accumulate in their bodies and cause severe eggshell thinning, among other health impacts. When peregrines sat on their eggs, they promptly broke them, effectively halting their reproduction and making the species an unfortunate poster child highlighting the hazards of DDT to living creatures. Rachel Carson’s influential Silent Spring unveiled the environmental crisis that postwar scientists had created: by attempting to better agriculture through the production of pesticides, they had inadvertently poisoned the world.

By the early 1970s, humans had decimated peregrine populations across much of their native range. In North America, they were extirpated east of the Rocky Mountains and south of the boreal forest; across northern Europe, only a few stragglers remained. The future for the critically endangered species looked bleak.

Amid the desperate handwringing that accompanied the regret of doing too little, too late, biologists identified a glimmer of hope on the northern horizon. Despite the absence of nesting peregrines, there were still regular sightings of the birds in the northeastern United States during fall migration; somewhere, somehow, these falcons seemed to be hanging on. The rallying cry was sounded: find out where the migrating peregrines had come from and whether they, too, were imperiled.

Researchers had a strong hunch and a smattering of historical reports to guide their search. Over the preceding decades, peregrines had been documented by Greenlanders and occasionally captured by enterprising foreign falconers who’d traveled by sailboat, cargo ship, or military plane to Greenland. Though a harsh and distant land in the minds of many policymakers, the island now offered a probable source of these fleet-winged ghosts.

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Like the peregrines themselves, Greenland is full of contradictions. The world’s largest island (excluding those deemed continents) is neither green nor especially land-like to most eyes, at least from a distance. According to the Icelandic sagas, Erik the Red—an exiled, Norwegian-born Viking—used this moniker as a 10th-century propaganda device to entice others to join him in a place largely covered in ice. Evidently, it worked. Norse settlers from Iceland arrived with horses, sheep, and pigs. They stayed for about 500 years, settling on the southern fringes of the Greenland ice sheet, which currently covers nearly 80 percent of the country and 1.2 percent of the planet’s terra firma, an area roughly three times the size of Texas.

Known also as Kalaallit Nunaat, or “Land of the People,” Greenland has also been home to Indigenous residents for more than 4,000 years, with multiple waves of migration from Arctic North America, followed by periods of apparent and largely unexplained human absence. The ancestors of contemporary Greenlandic Inuit, or Kalaallit—who today comprise most of the country’s population—likely arrived around the same time as the Norse and well before Denmark claimed Greenland as a colonial territory in the mid-18th century. Topographic maps and nautical charts reflect this complicated human history, with Norwegian, Danish, English, and Inuit place names layered atop 44,000 kilometers of fjord-cut coastline.

Today, Greenland operates mostly autonomously under Greenlandic Home Rule but retains strong ties to Denmark—including through its surprisingly rich, albeit largely colonial, history of bird research. Many early Danish missionaries to Greenland were avid birders who left detailed avifaunal records, augmenting those from visiting expedition leaders, civil servants, and physicians. The earliest Arctic bird-banding program originated in Greenland in 1926 and was later expanded to recruit local participants via an unusual fee-per-bird payment system. In 1954, for instance, the capture and banding of a peregrine falcon—kiinalleraq in the Greenlandic language Kalaallisut and vandrefalk in Danish—was valued at 4.8 Danish kroner, equivalent at the time to US $0.67.

The first formal study of peregrine falcons in Greenland began in 1972 in Kangerlussuaq (formerly Søndre Strømfjord), a west coast fjord where the ice sheet pulls away from the coast, leaving an abundance of nesting habitat. Americans William Mattox and William Burnham, both known familiarly as Bill, arrived to find a stable population of peregrines and the source of the mysterious fall migrants. Although peregrines breeding in Greenland were exposed to pesticides during migration and while overwintering at lower latitudes, they had extended periods to “detox,” which potentially explained why their exposure remained below the threshold that caused widespread reproductive failure elsewhere.

This chapter in ornithological history offered new promise for peregrines by suggesting that their numbers in the northern hemisphere were perhaps not as bleak as once projected. It also led to some of the longest-running studies of the species within its range, revealing new information about the birds’ nesting behavior, diet, and impressive migrations. Collectively, the two Bills, who were both eloquent and apparently unafraid of being deemed loquacious, wrote tomes about their findings.

Over the following several decades, dozens of graduate theses and research papers originated from western Greenland, shaping our understanding of peregrine falcons in the Arctic and elsewhere. Birds that nest in northern Greenland, for instance, make the longest migrations in the species’ range, with some individuals traveling to and from South America each year. Covering up to 900 kilometers a day, they’re not only impressive endurance athletes but also wildly individualistic in their habits, with routes that arc like spaghetti across the globe. Though peregrines often specialize in songbird prey, in Greenland they adjust their meal plans to match what’s on the table—readily swapping snow buntings for seabirds, redpolls for young hares. Where they’ve ventured farther north in Greenland, they join gyrfalcons in chomping on chunky little auks—small relatives of puffins that number in the tens of millions and provide a seemingly limitless source of food to hungry Arctic falcons.

Though research in Greenland didn’t explicitly save peregrines from what once seemed an inevitable fate, it helped explain why they still had a fighting chance: peregrines will make a living any way and in any place they can. Their adaptability proved to be their superpower. This flexibility impressed even those who thought they knew peregrines best, and, in turn, sent a bevy of field biologists spinning toward their own private obsessions: with Greenland, with falcons, with abseiling down cliffs and braving summer snowstorms. Studying peregrines in Greenland requires an unconventional skill set—picking mosquitoes out of one’s oatmeal, dodging icebergs by small boat, guarding against talon strikes, and scaling rock walls as “a necessary means of transportation”—that attracts adrenaline junkies and hardcore naturalists alike.

Since the Bills’ first survey in Kangerlussuaq, their commitment to conserving the species also extended well beyond the brief field seasons. Mattox spent many years advocating for peregrine recovery in both private and political spheres. And when Burnham wasn’t chasing peregrines in Greenland, he led captive rearing efforts in Colorado as part of the North American reintroduction program. The Peregrine Fund, founded by Tom Cade and later directed by Burnham, released the first captive-reared peregrines to the wild in Colorado and the East Coast in the mid-1970s. Over the next three decades, about 7,000 birds were reintroduced to North America, providing a critical boost to local populations. Many of the birds used in these captive breeding efforts were donated by falconers, with some likely originating from Greenlandic stocks.

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I’d hoped to see fieldwork on Greenland’s peregrine falcons in person, but the Denmark Strait had other plans for my family. We’d been poised to leave Iceland for weeks, reading daily ice charts and forecasts that declared repeatedly and unequivocally: not today. The rules for high-latitude sailing and Arctic fieldwork are similar: weather is king, and schedules are made to be changed. For us, getting to Greenland before the season’s end meant sailing north, rather than south, from Iceland and touching down in Scoresbysund, more than 1,500 kilometers from our original destination.

By the time we reach southern Greenland, I’m too late to meet Knud Falk and Søren Møller, a team of Danish biologists who began chasing Greenlandic peregrines about a decade after the Bills. Their commitment to falcons and the environmental lessons they can teach us has spanned 40 years; the research program they initiated in 1981 continues to this day.

“We tried to quit many times, but it never worked,” Møller jokes when I reached him later on a video call.

Though, in Falk’s words, they’d arrived “late to the party”—meaning the hazards of DDT were already well established—the pair’s contributions proved both timely and lasting. By collecting addled eggs and measuring eggshell thickness over time, they established an effective and tractable proxy for levels of DDT and its metabolites in Greenlandic peregrines. They later collaborated on studies of other emerging chemical contaminants, such as flame retardants and per- and polyfluoroalkyl substances (more commonly known as PFAS), some of which have been transported remarkable distances—by air, water, or the even birds themselves—to appear in Greenland-nesting peregrines.

As Falk explains, “We’re not just studying [the peregrine] because it is a fantastic species, and ecologically a top predator, but because it helps us protect the environment for our kids. This sort of legacy is important.”

In the end, the recovery of peregrine falcons has proven to be one of the good-news conservation stories in recent history: we recognized a problem and we did something about it. DDT was banned from agricultural use in most of North America and Europe by the early 1970s, allowing peregrines and other species to rebound with help from captive rearing. In 1999, peregrines were removed from the US endangered species list.

More recently, Falk and Møller’s data contributed to the listing of BDE-209—a carcinogenic flame retardant—under the Stockholm Convention on Persistent Organic Pollutants, once again making Greenland’s falcons key sentinels for the impacts of chemical compounds on our ecosystems. And in Sweden, where Falk now lives, the peregrine has become such a recognizable icon of environmental stewardship that it is used as a symbol for the Swedish Society for Nature Conservation and as a label on foods that have been sourced sustainably.

Yet just because a species has survived one gauntlet doesn’t mean its future is secure.

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After the initial frost-laced morning when we spot our first Greenlandic peregrine, my family spends a week anchored in Tasermiut Fjord. It is, as the harbormaster from the nearby town of Nanortalik describes, one of the most beautiful places on Earth. It’s also thick with peregrines. In three of the four valleys we explore by foot, we find territorial birds. After the young fledge, peregrine families remain near the aeries for several weeks, chasing away perceived threats such as ravens, eagles, and humans. Though we aren’t close enough to elicit their signature dive bombing—or, in turn, to require helmets—my sons quickly learn to recognize the peregrines’ defense calls, and to train their binoculars on the cliff walls in hopes of catching a glimpse. We record each nest sighting to add to Falk and Møller’s database.

Mine aren’t the first, or, by any stretch, the most dedicated ornithologist’s children to help collect local peregrine data. When I speak to Burnham’s son, Kurt, by phone in late August, he recalls a childhood shaped by falcons. He describes a photograph of himself in a crib at 10 days old, with a fuzzy-headed peregrine chick by his side; while Kurt’s mother was in labor, this sharp-beaked surrogate sibling was pipping from its egg. One of Kurt’s chores around the time he was elementary school was to help imprint young peregrines that would later be used for captive breeding. “Once the falcon chicks were big enough to walk, I’d tow them around in the back of my Tonka trucks,” he explains.

As savvy with peregrines as most contemporary teenagers are with TikTok, 16-year-old Kurt was an eager and well-qualified field assistant. Following in his father’s footsteps, he began his career in Greenland in 1991. Soon after, the Burnhams moved their primary study area to northwestern Greenland, centered on a site known today as Pituffik Space Base (formerly Thule Air Base). The father-son team worked together until Bill’s untimely death in 2006 from brain cancer, at which time Kurt took over—and expanded upon—the decades-long family legacy. (The other Bill, Bill Mattox, continued peregrine research at Kangerlussuaq until 1997 and chased falcons elsewhere until his death in 2020.)

More recently, the Burnhams ushered yet another cohort into Greenlandic fieldwork. In 2019, Kurt and his wife Jennifer, a geographer who also conducts research in Greenland, brought their eight- and 10-year-old sons—the same ages as mine are now—to Pituffik. Counting Kurt’s grandfather, who’d accompanied Bill as a field assistant many years earlier, that season marked the fourth generation of Burnhams to follow falcons in Greenland.

Just as caring for a species is intergenerational work, so too can it take many generations to right an environmental wrong. We refer today to DDT and related compounds as “legacy contaminants” for their longevity; five decades after they were largely banned from use in the northern hemisphere, they persist in many ecosystems. Although eggshell thickness has steadily improved in Greenlandic peregrines, Falk and Møller project that it won’t return to “normal”—pre-DDT—levels until 2034.

Meanwhile, peregrine populations in North America are trending downward for the first time since the 1970s. Scientists aren’t sure of the culprit, but the drop could be caused by avian influenza, a decline in prey species, or contamination by neonicotinoid pesticides or flame retardants. Environmental contaminants also loom on the Arctic horizon, including mercury, flame retardants, and PFAS, some of which Falk, Møller, and Burnham have documented in nesting falcons. Mercury concentrations in Greenlandic peregrines, for instance, rival those measured anywhere else in their range. And as in other parts of the Arctic, climate change is the undeniable woolly mammoth in the room, its heft now sitting squarely on Greenland’s back.

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The common phrase “front lines of climate change” has a strangely militaristic undercurrent—one that seems out of place in the version of Greenland that I experience. Nonetheless, there’s a sense of urgency here, a startling tenuousness to each day. Glaciers crack like artillery in the distance, while bergs the size of small cities drift by on satellite images; it’s hard to ignore melting ice when it emerges from the fog to tower three stories above our sailboat. On land, changes are also evident, albeit less striking in form: from the encroachment of shrubs on tundra to unpredictable patterns of precipitation to the rapidly growing demand for tourism, the “new Arctic” is rising fast.

For Greenlandic peregrines, the impacts of warming are decidedly mixed. All of the researchers I spoke to emphasized that extreme weather events, including heavy rainfall and large temperature swings, can be fatal for nesting birds. Kurt Burnham describes heart-rending footage of a female peregrine brooding her chick in a downpour: “She did everything she could to keep the chick dry, but it died in the end. She had to throw it out of the nest.”

Warmer summers have also given rise to new residents such as mosquitoes, which have moved into the Pituffik area within the past two decades. Besides being nuisances, mosquitoes can carry diseases such as avian malaria, which, though not yet detected in Greenland, has infected falcons elsewhere in their range and decimated other bird species on remote islands. Even insects themselves can be deadly. In northern Canada, for instance, peregrine nestlings have been killed by hordes of biting black flies, whose abundance has been linked to warming-induced weather events.

Despite such challenges, peregrines have again demonstrated a remarkable ability to adapt. An increasing number of peregrines have nested at Pituffik over the past three decades, with birds venturing hundreds of kilometers north of their previously described range limits and possibly even edging out long-resident gyrfalcons. This trend is likely to continue, eventually making Greenlandic peregrines among the most polar of their species. As the ultimate shapeshifters of the avian world, such flexibility bodes well for their future. Though the warming Arctic may test their limits, “peregrines … are one of the generalist species that will likely survive,” predicts Travis Booms, a raptor biologist who has studied falcons across their Arctic range.

Meanwhile, with retirement on the horizon, Falk and Møller worked with Pinngortitaleriffik, the Greenland Institute of Natural Resources, to secure funding for a research position to continue monitoring how Greenlandic peregrines respond to environmental threats. As Falk notes, transitioning the project to a Greenlandic organization not only makes logistical sense but helps ensure its longevity. Despite a long history of coexisting with falcons, Inuit residents and their knowledge have been largely neglected in published bird surveys and reports. Most ornithological research in Greenland has been conducted by foreigners, creating a scattershot scientific record and limited local engagement. This is slowly changing, as evidenced by recent studies using Indigenous knowledge to document changes in fish and wildlife populations, as well as Greenlandic representation on circumpolar working groups. In this era of extinction, we need all hands on deck.

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Continuing up the west coast of Greenland after our week of following falcons in Tasermiut Fjord, my eight-year-old finds a peregrine feather on the tundra below a guano-smeared cliff. Eyes trained upward, I scan for falcons. This time, I hear no criii-criii-criii from above, see no hovering wings or streaks of motion. The birds have apparently moved on, leaving only gray clouds and silence.

Written in the peregrine’s graceful flight is a story worth recalling: the possibility of redemption, the promise that the rarest of the rare may once again become blessedly common—if we care enough to act quickly. Across their expansive range, the birds plummet from the sky like exclamation marks, declaring we are still here.

When global peregrine populations still hovered on the cliff of extinction, Bill Mattox wrote: “I hope that our river cliffs and streams will once again be used by peregrines … I would like my sons to experience what I consider one of nature’s greatest thrills—seeing wild falcons hurtling through the air near their nesting ledges.”

Mattox’s hope was realized, thanks in part to the dedication of biologists like him; now, it’s up to us to decide what comes next.

Every generation leaves a legacy, a feather in the sand. Resting on my sons’ small shoulders—and all of ours—is the future of Arctic-nesting falcons and the dozens of other species that call this region home. What stories from the field will our grandchildren tell? Who will be their heroes, armed with Tonka trucks and climbing harnesses?

The outcome depends on far more than a new cohort of biologists. It will take a global frameshift to stem the carbon output that is heating our planet faster than we can document it. It will take many lifetimes to correct our environmental missteps. But progress is incremental and motivation personal—perhaps we should measure this shift not only in tonnes of invisible carbon dioxide or centimeters of sea level rise, but in terms that speak from the heart: one nest, one love affair, one falcon aficionado at a time.