Wild Pigeon Chase

As urban pigeons drive their wild relatives extinct, scientists are grappling with the definition of what a species is — and what it means to be truly wild.

Velvet Spectrum for Noema Magazine

Carrie Arnold is a freelance health and science writer living in Virginia.

NORTH UIST, Scotland — For the millionth time, I asked myself what I was doing out here. Roughly fifty miles off the west coast of Scotland, the late September winds shrieked and flung sleet at my head. A rivulet of rain dripped off my hat and down my back, mixing with a cold sweat that was part physical strain and part nerves.

The temperature had plunged to just above freezing. I stared at my husband who, like me, had rolled up his cargos to walk barefoot across the saturated sand, feet bright red from the cold and unwelcome North Atlantic exfoliation.

Along the horizon, a dark line of clouds promised to transform our existing difficulties into a fond memory. I watched as the incoming tide began to close in on our small strip of beach dividing the islands of North Uist and Vallay. If we wanted to catch a glimpse of the rare birds that we had journeyed thousands of miles to see — and make it back before the tide came in and blocked our return — we had to keep moving. Any bird, however, had been far smarter than us and had long since taken shelter. The only things in the sky were wind and rain and clouds.

It was an awful lot of effort for what was, essentially, a pigeon.

For millions of years, before humans domesticated pigeons for food, communication and companionship, these birds existed as rock doves. Across Europe and Asia, rock doves made their homes in small hollows on rock cliffs, scrounging nearby lands for seeds, plants, grasses and the occasional earthworm or insect to eat.

Most modern rock doves now live in cities, descendants of escaped domestic birds that have since gone feral, with a few remaining strands of “wild” DNA buried deep in their cells. Even in more sparsely settled rural areas, the birds identified as rock doves were as much pigeon as they were wild birds.

“This process is irreversible,” says Will Smith, an ornithologist and postdoctoral fellow at the University of Helsinki. “Once it happens, we can never get the originals back.”

Except in the Outer Hebrides. A rocky archipelago that stretches 150 miles from north to south, some 27,000 Scots continue to call this wind-whipped stretch of land home. And as scientists discovered just a year and a half ago, so too do what is likely the world’s only remaining population of wild rock dove that hasn’t interbred with feral pigeons.

This makes these rock doves incredibly rare — and incredibly endangered. Vallay was one of their strongholds, and Smith, who has spent the last five years studying the species on Uist (pronounced YOO-ist), had sent me a detailed GPS map of how to hike there. For a new but dedicated birder, it sounded like the opportunity of a lifetime. 

Watching the charcoal clouds and incoming tide approach, however, I began questioning my decision. Why was I slogging through gale-force winds, near-freezing temperatures and pouring rain with bronchitis to see a rare rock dove? Had I embarked on a wild pigeon chase? The two birds are, after all, the same species. It’s not easy to discern a wild bird from a feral urbanite.

Only when Smith clued me in to the subtle differences in beak shape and feathers on the rump and wings could I begin to tell them apart. Though their behaviors aren’t identical, both pigeons and doves eat the same foods and play the same ecological role. To philosopher Henry Taylor at the University of Birmingham, dividing Columba livia into two different groups — pigeonholing them, if you will — was an exercise based on human values, not biological or ecological differences.

“We tend to think a species has some kind of essence, that if we allow other organisms to breed with them, we’re going to dilute that. It’s not a very good way of thinking about species,” Taylor says. And if subdividing C. livia into two species was an effort in futility, then maybe Uist’s rock doves can count the world’s hundreds of millions of pigeons as their brethren and aren’t endangered at all. 

Smith, however, disagrees. The transformation of wild rock dove to urban or domestic pigeon changed the birds in subtle but significant ways, such as making them less wary of humans and allowing them to produce more clutches of eggs during the year. Pigeons are essentially a human creation; rock doves aren’t. Genetic studies of Columba livia show that the wild rock doves of Uist are potentially at risk of extinction thanks to extensive mixing with feral pigeon populations.

“Pigeons are essentially a human creation; rock doves aren’t.”

What makes rock doves special, he says, is their hidden archive of genetic diversity and a historic record written in their DNA that may help scientists tease apart why some animals adapt so well to humans. The wild doves also provide a reserve of genetic diversity that can help the birds fight off a wider range of pathogens and adapt to changing conditions due to urbanization and climate change. To help save his beloved birds, Smith would have to learn what made these wild birds so special — and so distinct from their more cosmopolitan counterparts. 

“Because nobody has looked at them in depth before, every little thing we find out is brand new and exciting,” he says.

My search for wild rock doves, then, not only traced a path to an uninhabited island but also through the debates sitting at the heart of conservation. With so much need and so few resources, we all must decide what species are wild and worth saving. And those answers will have life-and-death consequences.

Country Or City Bird

In 1880, archaeologists excavating the Mesopotamian city of Sippar (located on the outskirts of modern-day Baghdad) discovered a fist-sized chunk of clay. Inscribed on one side was a series of hash marks in ancient cuneiform, an account of the purchase of barley as “bird fodder.”

This artifact, in the collection of New York’s Metropolitan Museum of Art, is part of a series of etchings, documents and hieroglyphics documenting the some 5,000-year history of pigeon domestication. Genetic studies push this history back even further, to a 10,000-year fellowship between pigeons and people, predating the domestication of all other birds, including chickens and ducks.

Although scientists can’t pinpoint exactly why humans first invited wild rock doves into the Great Indoors, they do know that the peoples of the Near East raised pigeons for food (I found an ancient Sumerian recipe for pigeon soup recreated by a modern chef). People also used pigeons for their homing ability which enabled them to navigate back home from an unfamiliar location over vast distances. This trait made the birds useful for dispatching messages between far-flung settlements.

Whatever the initial motivation for domestication, pigeons thrived with humans. “I think they’re one of the top 10 animals that has learned to live best with us,” Smith told me.

But the dividing line between the domestic pigeon and wild rock dove was never firmly fixed. Some pigeons escaped their confinement and began interbreeding with other erstwhile domestic refugees. Homing and racing pigeons could get lost or blown off course.

Since populations of rock doves were so large and widespread, many of the erstwhile domesticated pigeons went feral and began breeding with wild rock doves. Once these erstwhile domesticates began interbreeding, their elaborate plumage — such as dramatic leg feathers that make the pigeon look like it’s wearing pantaloons — had reverted to a state much closer to their wild counterparts.

Skyscrapers and multi-story buildings that dominate modern cities provide shelters analogous to the rock cliffs where doves have historically lived. What’s more, the doves’ predilection for carbohydrate-rich foods enabled them to dumpster dive for food scraps. Pigeons could raise three-to-four large clutches of eggs each year, compared to two smaller clutches produced by wild rock doves. Rapid urbanization over the past century combined with the fecundity of pigeons has, it seems, put feral and domestic pigeons at a huge advantage over rock doves.

“While we think we know them very well because pigeons are everywhere, we know almost nothing about the wild doves,” says Germán Hernández Alonso, a postdoctoral fellow in evolutionary biology at Uppsala University. Hernández Alonso points out that, for all the thousands of papers published each year on domestic pigeons, there’s far fewer in-depth studies on rock doves in all of science.

Nonetheless, rock doves and feral pigeons are the same species, however much we might try to distinguish them (by, say, labeling them “doves” and “pigeons”). Part of what makes them different has to do with the pigeons’ domestic history and the indelible imprint of humanity. Since the rise of the Industrial Age in the late 1800s, Americans have placed humans as outside of nature, says Roderick Nash, a retired environmental historian from the University of California, Santa Barbara. This ethos was ultimately enshrined in the 1964 Wilderness Act, which protected land “where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain.”

“What makes rock doves special is their hidden archive of genetic diversity and a historic record writ in DNA that may help scientists tease apart why some animals adapt so well to humans.”

“Civilization created wilderness,” Nash says. “The Neanderthals wandering around didn’t think of it as wilderness. They thought of it as where we live. It was only when humans came and began to put lines on the land that they drew lines in their minds.” 

This line-drawing has filled so-called wild animals with a mystique that livestock lacks, Nash says. I realized, in talking with Nash, that it was the wildness of the rock doves that made them so attractive. But that didn’t mean my search for wild rock doves wouldn’t take me on some very wild adventures.

Rise Of The Pigeon

In the 1970s, scientists on Sardinia began tracking the island’s remaining wild rock dove populations. Initially, they found that although the birds in cities and towns were mostly pigeons, wild rock doves continued to dominate in less densely populated areas. Over the next few decades, however, that shifted dramatically as feral pigeons outbred wild doves. By the 2010s, the rock doves on Sardinia were mostly feral pigeons. Ornithologists across Europe came to similar conclusions. “This huge, healthy population in the Mediterranean just collapsed,” Smith says.

The wilds of northern Scotland told a different story. On a research trip to the north coast, Smith kept spotting birds without the tell-tale feral speckles. He began to wonder whether a few wild birds had managed to hang on amongst the hills and heather. Research from Sardinia told him that more isolated locations far from large cities were most likely to yield wild rock doves. So he asked local birding groups across the UK and Ireland to identify any doves without the wing speckling characteristic of feral pigeons.

Individuals certified as bird ringers (what Americans call bird banders, those individuals who are trained and licensed to place small, labeled metal rings around a bird’s leg to enable tracking) also provided some feather samples from the doves. Cells on the end of the feathers allowed Smith to sequence their DNA.

At first, Smith’s PhD project looked like a recapitulation of the work done in Sardinia. Even in sparsely populated corners of the Scottish Highlands and islands like the Orkneys and Shetland, the genetic makeup of the birds Smith found were more pigeon than dove. But when Smith examined the DNA found on feathers gathered on North and South Uist in the Outer Hebrides, he found something different. Those rock doves showed almost no signs of interbreeding with pigeons. 

“These guys are special,” Smith says. “They’re like a blank slate for science.”

Journey to Vallay

Until I read Smith’s 2022 paper on his Hebrides discovery, I hadn’t given much thought to pigeons or their wild ancestors. But these distinctions didn’t help me understand why the doves had hung on in Uist and why these particular birds were so special. My husband and I had been planning a trip to Scotland, and so I convinced him to take a detour to the Outer Hebrides so I could see for myself. I didn’t mention that we would need to hop on two ferries in order to seek out a glorified pigeon.

I regretted my powers of persuasion immediately upon stepping onto the second ferry. The tail end of a powerful tropical storm was churning up the North Atlantic and our aging ferry pitched among angry gray waves. I clutched a seasickness bag for dear life.

Four hours later, we drove off the boat and into the inky blackness of the town of Lochboisdale on South Uist. Even with all the accouterments of modern technology, the trip was challenging. For the pigeons, flying from Scotland would have meant navigating over 60 miles of open water and fighting strong winds that barreled off the ocean. The odds that an errant pigeon would somehow arrive on Uist felt vanishingly small.

As dawn broke the next day, I pulled up Smith’s list of the best places to see rock doves and compared it with our map of the islands. Both Smith and other birders I had emailed from the area confirmed that the rock doves were easy to spot. “Can’t miss ’em,” Smith assured me.

The best place to start my search would be Vallay, an island accessible from North Uist by crossing a nearly two-mile-wide sandbar that emerged from the water for two to three hours a day during low tide. Planning the excursion on a cozy sofa with a steaming cup of Earl Grey made it seem manageable.

“With so much need and so few resources, we all must decide what species are wild and worth saving. And those answers will have life-and-death consequences.”

The weather had different plans. Shrieking winds made it hard for my husband and I to remain upright on the open beach, and that was before factoring in the pelting rain and frigid temperatures. Worse, the ground was so saturated with water that it functioned as quicksand, suctioning us up to our knees with every step, so that we had to quickly hop up on another leg in an exhausting dance I dubbed the Vallay High Step. I stopped thinking of birds and simply thought of putting one foot in front of the other.

The agonizing slowness of our progress forced us to make a game-time decision while only about two-thirds of the way across the land bridge. With worse weather on the way and running out of time, we decided to play it safe and Vallay High Step ourselves back to the car. Later, Smith told me we had been smart. Not only were we unlikely to see any doves in the abandoned buildings on Vallay due to the weather, but several people had also died when making the same crossing amid poor conditions. Still, I was frustrated. How hard could it be to find a freaking pigeon?

Extinction By Hybridization

For conservationists, hybridization is a double-edged sword. Genetic analysis has revealed that, far from being a rare anomaly, crossbreeding between two different species is quite common in the natural world. It can be the first step in the creation of a new species, Claudio Quilodran, a conservationist and evolutionary biologist at the University of Geneva, explained to me. It can save a small population from the genetic problems of inbreeding when conservationists deliberately import more distantly related individuals to freshen the gene pool in a process called genetic rescue. But hybridization can also be the death knell for a species on the brink of extinction.

In Scotland’s Cairngorms National Park, about 200 miles due east of Uist, the world’s last remaining Scottish wildcats eke out a living. Even before humans and their housecats crossed the English Channel, the wildcats were almost identical in appearance to an average tabby. A recent study in Current Biology found that over the last 60 to 70 years, as wildcat numbers have plummeted, the remaining cats have begun mating with unfixed outdoor domestic cats, spawning a population that is mostly moggy with only a hint of its wildcat ancestry. 

“Hybridization can change things very, very quickly,” says Quilodran. “With Scottish wildcats, it happened in less than 100 years.” 

Just like on Uist, an animal domesticated by humans was overwhelming its close wild relative. That this is happening is being written (and overwritten) in the billions of As, Ts, Gs and Cs in the DNA of their cells. What’s harder to measure is how much it matters.

“Species deserve to have their own evolutionary process without human interference,” Quilodran says.

Conservation decisions have hinged on the definition of hybridization. Beginning in the 1940s and 1950s, the use of the pesticide DDT, flooding and diking of the area’s marshlands to prevent mosquito breeding and the development of Florida’s Cape Canaveral had served to nearly wipe out the dusky seaside sparrow. By 1980, only six birds remained, all of which were male. Crossbreeding the remaining dusky sparrows with another similar Florida bird known as Scott’s seaside sparrows resulted in viable offspring; it seemed possible that the dusky sparrow could be saved, albeit in a modified form.

But the U.S. government ultimately ruled that such hybrid birds threatened the dusky sparrows and declined to protect the hybrids. Both birds ultimately went extinct. In a paper for the Boston College Environmental Affairs Law Review, attorney Kevin Hill and a then-professor at the Ohio Northern University School of Law, wrote that when “presented with the choice of a 98.4% pure Dusky or none at all, the [U.S. Department of the Interior] Solicitor chose extinction. To save an abstraction of the species, the reality was allowed to die.”

For Smith, however, his work with wild rock doves isn’t about some artificial notion of genetic purity. Rather than trying to save some idealized ur-pigeon, Smith’s goal is to preserve the biodiversity of wild rock doves. The process of domestication involves a lot of inbreeding, which quickly strips much of the innate genetic variety out of a species. Since urban pigeons are largely descendants of domesticated birds, they don’t have the underlying genetic variation that’s key to a species’ health.

“The process of domestication involves a lot of inbreeding, which quickly strips much of the innate genetic variety out of a species.”

“Where we have different populations with different histories, we can ask deeper questions about extinction and hybridization,” Smith says. “And the more we can understand this process, the more we can learn about how to kind of mitigate its impacts across more than just this one species.”

Doves In The Wild

After our aborted mission to Vallay, I decided to try looking for rock doves in tamer landscapes. Our first stop — some abandoned outbuildings on a working farm in South Uist — was a flop. I staked out the stone barn in our rental car with my trusty binoculars, but no birds appeared. I reluctantly crossed off that location and moved northward.

Several wrong turns later, a friendly local gave us some cheerfully vague directions that involved taking the first left after the fourth cattle gate. Here, a sheep field butted up against a rocky beach and the North Atlantic. Scanning the beach from the passenger seat, I saw plenty of birds, including the vibrant orange beaks and black and white plumage of oystercatchers, numerous species of gull, and ever-present kittiwakes. Nowhere, however, was there a dove.

No sooner had I opened the door to grab our lunches out of the backseat then a startled flapping of wings greeted me. I didn’t even have time to grab my binoculars before the bird disappeared into the grass. I didn’t need them, though. I was close enough to recognize the brief flash of purple iridescence and thick black wing stripes of a rock dove without them. Giddy with excitement, I scoured the fields for any feathered friends. I saw a few birds in the distance but nothing with certainty. After wandering the beach amongst the shorebirds, we finished our sandwiches and headed further north, just east of where we had attempted our Vallay crossing the day before. 

As soon as we turned off the main road and onto a small track, we began passing rock doves. Just like Smith had promised, you couldn’t miss them. We found a place to pull off by an aging burial ground and a large farm. No sooner did we park than the birds decamped from the cemetery and moved to a hilltop 50 yards beyond. Struggling to scramble up the hill while shrugging on my jacket, I followed in pursuit.

No matter how carefully I walked or how gently I approached, the birds moved another 50 yards back every time I got a few feet closer. I tried approaching again, slower still. The doves continued to back away. The more I followed, the farther the birds got. I had no way of getting close enough to see if these birds carried the small metal bands on their legs that Smith and his team had placed on several hundred the year before. 

These doves weren’t living in some pristine wilderness. It was a working landscape. I trotted by several startled sheep and saw tramlines where fields had been plowed. Signs of human life were everywhere. The secret to finding these seemingly wild birds — and staying alive to tell the tale — was not to get as far away from human habitation as possible but to stay a bit closer.

It’s just this duality that conservationists are also beginning to embrace, that humans are of this world even as we are inexorably changing it (and not often for the better); that animal species around us aren’t perfect museum specimens but a messy scattershot of mixed bloodlines; and that “wild animal” is as much a human construct as any single species or pure genome. This chaos is so much of what makes nature special and worth protecting.

I could chase my wild doves forever, it seemed, and they would always be flying farther and further away, always just a bit wilder than I could manage.