Migrationland | Down East Magazine

The Naturalist in Migration Land

Pulitzer-nominated author Scott Weidensaul calls Maine “a major bird factory.” His much-anticipated new book explores the mysteries behind birds’ migration routes — and the human-caused disturbances that threaten them.

By Rachel Slade | Photographed by Tristan Spinski

One day last fall, author and naturalist Scott Weidensaul drove across the border from his home in Milton, New Hampshire, with his Subaru Outback pointed Down East, towards the Petit Manan peninsula. Most of the little-populated cape, on Dyer Bay, near the fishing community of Milbridge, is part of the Petit Manan National Wildlife Refuge, a nearly 7,000-acre complex of island and mainland parcels that protects some of Maine’s most diverse and valuable coastal habitat. Since 2015, a handful of researchers and volunteers have gathered there each October to spend night after night catching tiny, mottled owls called northern saw-whets, which visit the peninsula by the thousands during their fall migration from the boreal forests of the north to a range of forest ecosystems in the central and southern U.S. Many of the details of the trip remain mysterious to researchers — until about a century ago, in fact, northern saw-whet owls were thought to be nonmigratory. Weidensaul was spending the weekend helping to net, tag, and release the birds, collecting data for an international effort called Project Owlnet, which hopes to dispel some of the mystery. 

Author and naturalist Scott Weidensaul; the research field station at Petit Manan National Wildlife Refuge.

Weidensaul has spent most of his life studying bird migration, trying to answer fundamental questions about the billions of creatures that take to the air and travel tremendous distances each year. His 1999 book Living on the Wind: Across the Hemisphere with Migratory Birds introduced readers to the subject as science then understood it. It earned Weidensaul comparisons to Rachel Carson and John McPhee, and in 2000, it was a Pulitzer Prize finalist. But even 20 years ago, scientists knew far less than today about the precise routes that various species take to reach their wintering grounds and return to their breeding grounds, about how birds navigate these routes, and about how some species manage to spend unimaginable percentages of their lives in the air. What they did already know is that North American bird populations are shrinking — decades of Doppler radar images captured during migration seasons prove this beyond a doubt — and that many birds seem to disappear during their intercontinental journeys. Efforts to protect them, however, were long stymied by our lack of knowledge about migration. 

Until recently, bird banding was about the only tool researchers had to learn about the intricate, millennia-old networks of avian flight paths. Since the time of John James Audubon, scientists have worked with volunteers and assistants to catch individual birds, affix a band with a unique ID number to their delicate legs, record the number, and then release the birds — and hope. A tiny percentage of the banded birds are found by strangers; a small percentage of those strangers report their finds to the banding organization. Using this fragmented data, generations of scientists have tried to piece together a story of migration. It has been, in Weidensaul’s words, “a long slog.” 

Nets at Petit Manan.
Saw-whet owls are nocturnal and good at avoiding detection.

But 21st-century microtechnology and geolocation capabilities have turbocharged the study of migration. While old-school banding is still a key tool — the more state-of-the-art approaches being pricey — some researchers can now track individual birds as they travel across continents and over oceans. In fact, they can track individual wingbeats. In 2010, researchers using geolocators were astounded to discover that some Arctic terns tagged in the Netherlands had traveled up to 57,000 miles in a year — more than twice the distance that scientists thought possible. They flew as far as Australia, stopping over at islands in the Indian Ocean, where terns tagged in coastal Maine have also been found.

Information gathered over the past two decades has radically transformed conservation efforts, which once focused on saving Amazonian and North American forests but have now expanded to target critical, if sometimes little-heralded habitats along migratory corridors. On shelves in March, Weidensaul’s new book, A World on the Wing: The Global Odyssey of Migratory Birds, tells a much more nuanced story about how bird populations move around our planet. It also offers a sobering look at how anthropogenic climate change and habitat destruction are fueling those populations’ decline, examining how entire species can be compromised when their stopover points are developed or contaminated, how very small pieces of land — like Petit Manan — can make the difference between survival and extinction.

Saw-whets are lured by an audio recording of a male owl’s breeding song.
After their data is recorded and a band affixed, the owls are released unharmed.

Saw-whet owls, biologists believe, are one species impacted by habitat loss. But it’s hard to say for sure, because little saw-whets are sneaky. They are nocturnal, silent during their migrations, and adept at camouflage. Until the mid-1990s and the advent of Project Owlnet, they were thought to be rare. Turns out, they are fairly abundant but hard to notice. One Maine ornithologist has dubbed them “the invisible owls.” Last year, Weidensaul told a podcast, “I love saw-whet owls as an object lesson about how little we know about even the most common species of birds.” Their enigmatic nature is part of what brought him to Petit Manan — and why I was glad he invited me along.

I trailed Weidensaul’s Subaru down a winding dirt road through the Petit Manan refuge, stopping here and there to swing open gates meant to keep out unauthorized vehicles. Surrounding us was a mix of meadow, stunted American mountain ash, low birch and aspen, and fruit-producing native shrubs. It’s what’s known as an early successional habitat, a quick-growing, scrubby landscape that requires constant disturbance — in this case, high winds carrying salt spray — to prevent maturation into full-fledged forest. Many juvenile birds are drawn to early successional forests for their nutrient-rich fields of huckleberry and blueberry and their thickets of saplings and brush. It’s a place where they can bulk up while staying relatively safe from predators. Maine’s 3,500-mile shoreline boasts an abundance of this dense, nutrient-rich habitat.

To a casual visitor, the windswept peninsula may seem little occupied, but to a sharp-eyed naturalist, it teems with life. Here and there, Weidensaul hit his brakes, threw his wagon into park, and pointed out the window towards the underbrush, shouting out species names — “ruffed grouse!” “sharp-shinned hawk!” — so I’d know what to look for. I stared dutifully into the shadows until I connected with eyes staring back at me.

Zoe Korpi spent most of last fall capturing and banding saw-whet owls on Maine’s Petit Manan Peninsula.
Scott Weidensaul’s new book, A World on the Wing: The Global Odyssey of Migratory Birds, unpacks one of the planet’s most conspicuous and least understood phenomena.

When we arrived at the banding station — a small, white, off-grid camper parked in a clearing — Weidensaul noted the name of the road we’d come in on: Pigeon Hill Road. “That’s not city pigeons they’re talking about,” he said. “It’s passenger pigeons. Presumably, prior to extinction, this was a stop-off point for migratory flocks passing through New England.”

Maine remains “a major bird factory,” he said, with a largely healthy coastline offering both mature and early successional forest and with birds passing through each year in the tens of millions. “The numbers are staggering and seem incomprehensible,” Weidensaul said, “because most of the migration is taking place at night.” Still, it’s a fraction of what would have been happening 50 years ago, never mind 350 years ago. If he ever got his hands on a time machine, Weidensaul told me, he’d want to witness a pre-Columbian migration in North America.

“It must have been astonishing,” he said, wistfully, “with species we don’t have anymore.”

Examination of the wings under black light can help determine the age of the owls…
…which are small enough to fit snugly in a 6-ounce can while being weighed.

Outside the camper, we met “resident bander” Zoe Korpi, a 22-year-old graduate student from Pennsylvania, along with a volunteer who’d driven up from Cape Cod for the weekend. After introductions, Korpi led us into the forest to deploy six nets. Each was 40 feet long by 9 feet high, she explained, to be laid out in a zigzag pattern across narrow lanes cut through the saltspray-stunted woods. Weidensaul mentioned that mist nets like these came from Japan and were originally made of human hair. They were so effective at catching birds that, under Clinton, the U.S. convinced the Japanese not to sell them except to buyers with conservation goals. The Chinese now manufacture similar nets and sell them to anyone — another example of a man-made threat to the avian populations.

In the woods, Korpi unfurled the nets using a custom-designed pulley system and turned on the “audiolure,” a solar-powered speaker blasting a recording of a male saw-whet’s come-hither song. Suddenly, the trees around us were full of high-pitched “too-too” whistles, repeated every second for countless rounds, like the sound of a truck’s backing-up alarm. Researchers started using nets with audiolures in the late ’80s, and the pairing quickly proved that the elusive birds weren’t as rare as once thought. One of the method’s pioneers, Maryland ecologist David Brinker, founded Project Owlnet in 1995 and recruited Weidensaul as a codirector two years later.


Weidensaul has been banding northern saw-whet owls ever since, but he was particularly excited about last October’s visit to Petit Manan, his first. Every four years or so, the number of migrating saw-whets swells dramatically, a consequence of trees in their breeding grounds having produced an abundance of cones, fruit, and nuts the year before. Such cyclical “mast years” fuel population booms of small mammals, meaning more food for saw-whet hatchlings and juveniles the next spring. Consequently, owl populations surge, leading to a mass flight in the fall, known as an irruption. In the eastern U.S. and Canada, 2019 had been an epic mast year. If the wind was favorable, Weidensaul predicted, either calm or northerly, owls could be flying over the Maine coast in remarkable numbers.

It was dark when we finished securing the nets, and we trekked back to the camper by flashlight to wait. We would check the nets for owls every 30 minutes for the remainder of the night. 

Though he lives a few miles on the wrong side of the Maine–New Hampshire border, Weidensaul is no stranger to Vacationland. As an instructor and director of the ornithology program at Bremen’s Hog Island Audubon Camp, he’s come to the midcoast every summer for 22 years. He co-edited last year’s Birds of Maine, an encyclopedic guide to the state’s avian life, and he’s given talks and presentations from York to Schoodic. In June, he’s scheduled as a keynote speaker at the Acadia Birding Festival.

Weidensaul, who is 62, grew up at the base of the Appalachians in east-central Pennsylvania, just a mountain ridge away from the coal-mining region. As a boy, he would climb to the top of Ashland Mountain, behind his house, and look north to where the land had been deep-mined, then strip-mined in the 19th and early 20th centuries. The experience, he says, turned him into a conservationist at an early age.

In the autumn, researchers like Weidensaul and Zoe Korpi spend long nights netting and banding migrating saw-whets at Petit Manan.
Recording data before releasing the birds.

The oldest of three, he spent much of his youth turning over rocks and poking sticks into holes to root out wildlife. He filled his boyhood bedroom with aquariums and terrariums loaded with creatures he’d carried in from the woods. “My parents’ one rule was nothing venomous in the house because everything found its way out,” he says. He dreamed of becoming a herpetologist and remembers bare-handing copperheads and rattlesnakes. In retrospect, he says, he’s lucky he’s still alive. “When you’re a kid, you think you’re bulletproof. I did a lot of stupid stuff.”

Weidensaul studied art at nearby Kutztown University, hoping to become a wildlife artist. His interests confounded his advisor, who couldn’t understand why the young artist chose to take a mammalian-anatomy class and not a jewelry-making one. Eventually, school turned him off. “Everybody’s entitled to one really dumb mistake in life,” he says, “and mine was that I dropped out of college in junior year.”

Weidensaul handles a banded bird before releasing it. Saw-whet owls are famously docile.

Through a family friend, Weidensaul was introduced to Doug Costello, a onetime Mainer and former editor of the Aroostook Republican, then the editor of Pennsylvania’s Pottsville Republican. Costello hired Weidensaul to write a nature column, which led him to a decade-long stint as an investigative journalist.

Eventually, Weidensaul left the paper to freelance and refocus on his first passion: wildlife. He worked for Pennsylvania’s Hawk Mountain Sanctuary, the world’s first refuge for birds of prey, where he used pigeons outfitted in custom leather “flak jackets” to lure red-tailed hawks and golden eagles into nets for banding. Working with powerful raptors, with their extraordinary hearing and 400-PSI talon grip, was exhilarating. 

But when Weidensaul saw his first saw-whet owl in the mid-’90s, he fell hard for the pint-size, big-eyed, “astoundingly appealing” little migratory bird. Researchers could study birds on land and in their breeding grounds fairly easily, but the details of migration remained a mystery. Where did various species go? What routes did they take? How far did they travel? Where did they stop to refuel? The secretive little owls helped set Weidensaul on a path to try to answer such questions.

An hour after sunset, Korpi checked her watch and announced it was time to check the nets.

We switched on headlamps, zipped up jackets, and crossed the clearing to the woods in a huddle. Korpi moved quickly up the net lanes and was the first to see we had a couple of customers. The two owls hung upside down, entwined in the netting, each a softball-size fluttering of fluff. Korpi wrapped a hand around one of the birds to prevent it from flapping as she carefully unwound the fine net strands from its tiny talons. Then, she slid the bird into a mesh bag and pulled it closed with a drawstring. Weidensaul did the same with owl number two.

Korpi measures a saw-whet owl in the research trailer, prior to banding.

Back in the camper, Korpi removed the first bird from its bag and held its feet in a “photographer’s grip,” the legs between her index and middle finger, the upper toes pinched with her index and thumb. It was a female, she said, as most netted saw-whets are. Females and juveniles tend to migrate, while adult males usually stay put, staking out choice nesting holes and food sources that will ideally attract females when they return. Korpi’s saw-whet calmly looked around, and I got my first good look at it, a ridiculously adorable little feathered killer with huge golden eyes that blinked languorously, showing off long black eyelashes.

In a single swift motion, Korpi tucked the owl head-down into an orange juice can, perfectly sized for a saw-whet, and counted the tail feathers while noting the state of the plumage. The bird was on its second molt. She then weighed it, removed it from the can, and spread one wing, measuring it with a ruler taped to the desktop. She matched the eye color to a laminated paper with four Benjamin Moore paint chips in various shades of goldenrod: “oxford gold,” “golden orchards,” “bold yellow,” and “viking yellow.” Finally, she switched on a black light to examine the underside of the wing. 

Astoundingly, the feathers that appeared dull brown and beige in normal light glowed neon pink. Newer feathers shone brightly; older feathers appeared a deep purple. 

“It’s a combination of serious ornithology and a cheap party trick,” Weidensaul said. In 2011, he copublished the definitive paper about using UV light to age owls, explaining that shortwave light — which many birds see but humans cannot — causes pigments found in some feathers to fluoresce. For this reason, it’s possible that birds look very different to each other than they do to us.

Korpi used specialized pliers to fold a small metal band with a unique identification number around the owl’s leg. In the future, if someone nets or otherwise finds the bird, they’ll be able to look up that number and know that, in October 2020, this saw-whet visited a warm camper on the coast of Maine. 

The owl-tagging season would prove to be Petit Manan’s biggest since the station’s founding, with more than 450 owls banded before the end of October — a couple dozen more than during the last irruption, in 2016. Project Owlnet has some 125 other banding sites across the U.S. and Canada. Comparing data gathered there and at future sites will allow researchers to gauge population trends, help them delineate the still-
unknown extent of saw-whets’ wintering range, and allow them to gauge what Weidensaul calls the “threat landscape” — from development, climate change, and other forms of habitat degradation. As he writes in the new book, “These are creatures whose entire life cycles must be understood if we’re to have a prayer of preserving them against the onslaught they face at every moment, and at every step, of their migratory journey.”

Weidensaul carried our first saw-whet of the evening up the hill, away from the light of the camper to the edge of the woods. We stood in the crisp evening, admiring the stars. Birds navigate using the stars’ rotation and the Earth’s magnetic poles, he said. The bright lights of cities can disorient them, attracting them and drawing them off course. Weidensaul mentioned the dramatic example of New York City’s 9/11 “Tribute in Light,” twin beams of xenon-fueled light shot 4 miles into the sky every September 11, from dusk to dawn. Concerned citizens found that, each anniversary night, the light columns were drawing some 160,000 migrating birds into a death spiral. Countless birds died of exhaustion or starvation. In response, the NYC Audubon chapter began organizing teams of volunteers to monitor the number of songbirds, nighthawks, and falcons caught in the light. Now, whenever the avian horde whirling in the blinding beams numbers about a thousand, the memorial is turned off for 20 minutes, allowing the birds to escape.


Weidensaul checked his watch, making sure he’d given the saw-whet in his hand enough time in the dark for its eyes to adjust. The tiny owls don’t seem to know what to make of the primates who stick them in cans and bedazzle their legs, he said. Many northern birds, like saw-whets, spruce grouse, and ptarmigans, don’t seem programmed to fear humans. Some saw-whets simply hang out a while after they’re released, seemingly enjoying the night and the company.

When it was time, Weidensaul carefully placed the bird on my outstretched forearm, and I held my breath, hoping the diminutive raptor would find me a friendly perch. She flew off in an instant. “I guess you don’t have good owl energy,” Weidensaul said. We laughed and headed back to the camper for owl number two.

That one apparently found me appealing. Outside, Weidensaul set her on my arm and quietly stepped back. She perched there, nearly invisible in the darkness, and I stood in awe of this exquisite creature, plucked from the air, poked and prodded, now choosing to spend a brief moment with me at the edge of the woods. 

“Are owls smart?” I asked. Weidensaul said that, as far as we’re able to measure avian intelligence, owls, compared to corvids or parrots, aren’t the brightest. Sensing my disappointment, he added, “But they’re really good at being owls. And that’s all you can ask of an animal.” 

The saw-whet stayed, listening to the humans trying to figure it out, smelling our strange smells, perhaps seeing amazing things in the darkness with her giant, viking-yellow eyes. She stayed so long that my arm began to go numb, but I didn’t want to scare her away. So I stood still, trying to resist projecting my human thoughts onto the wild thing resting lightly on my jacket.

And then, in a heartbeat, with a tiny flutter of wings, she vanished silently into the Maine night.