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One of New York City’s little-known and mostly unseen wonders is that, in the dark of night during spring and fall, millions of birds fly directly over Manhattan on a migration path that their ancestors have been traveling for millennia. For some, the journey stops short here: Astonishingly, the city sees nearly 250,000 bird deaths from collisions with glass every year.  

As a bird enthusiast, I knew that the city’s position on the Atlantic Flyway makes it a risky place—that the built environment and a preponderance of glass create a dystopian house of mirrors for migrants drawn in and disoriented by electric lights. But I didn’t grasp the problem’s scale until, in 2020, I stumbled across a photo on social media of 26 birds that struck one building in a single morning. In an instant, the abstract idea of window collisions became concrete. I couldn’t remain a passive witness.

That fall, I began volunteering to log collisions with New York City ̽����ѡ’s . Started in 1997, the community science initiative puts boots on the ground during migration season to record birds injured or killed by window strikes. As with similar efforts around the country, trained volunteers walk prescribed routes at deadly hotspots citywide to collect comprehensive data about the victims they encounter. NYC ̽����ѡ uses the information to support advocacy, legislation, and research. 

When I first started leaving my house before dawn to comb the sidewalks around a cluster of buildings in downtown Manhattan, I was optimistically naive. I imagined Disney princess moments of swooping in to rescue injured warblers and sparrows. The actual narrative was much darker.

Though the city is barely simmering when I start, each morning is hectic: a race against building staff who sweep up evidence of window strikes and an awakening surge of cars, pedestrians, and cyclists, as well as hungry squirrels, gulls, and curious dogs. Searching sidewalks, awnings, and streets, I place injured birds in individual paper bags and collect dead birds in another sack. When I’m done, I take a 30-minute subway ride to drop off patients at Wild Bird Fund, the city’s only wildlife rehabilitation clinic, before heading back downtown to start my workday (my office is housed in one of the very buildings I monitor). Unfortunately, roughly 7 out of 10 birds I find are dead, and many I rescue eventually succumb to injuries.

Like other collision monitors I know, I now have dozens of slow-motion scenes etched in my memory. I see the Northern Flicker cartwheeling through the air to the pavement, shuddering, and then dying in my hands. I replay the giant lump of a Chuck-will’s-widow, a near-threatened oddity I never expected to observe alive in the woods, let alone dead in downtown Manhattan on a cool April morning. I rewind my recollections to see a squirrel devouring a stunned warbler, and the aghast face of a pedestrian as she registers that she just kicked a songbird down the sidewalk. 

Yet no scene haunts me more than that of September 14, 2021. Until then, I had collected at most a handful of birds along any single facade. As I exited the subway that morning, I saw dark shapes in every direction from half a block away, as if someone had strewn sacks of birds across the sidewalks. I’m not easily rattled, but for the first 10 minutes, all I could do was murmur, “Oh my god,” as my trembling hands scooped up carcasses. Across four World Trade Center towers, over a 92-minute whirlwind, I picked up 229 dead birds (primarily warblers), photographed another 40 on out-of-reach awnings, and collected 29 birds with injuries. Reports indicate that my tally was just a fraction of the citywide toll, all victims of what I learned was an unfortunate confluence of conditions: stormy, low-visibility weather; a heavy migration pulse; and brightly lit buildings serving as lethal beacons in the dark.

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ack home, in a surreal stupor, I shared my photos and a video to social media, thinking local birders might see them. Instead, local, national, and international media picked them up, making my day one of the most publicized mass-collision events in recent New York City history. My online followers surged, and the rest of September became a blur of interviews. I’d unintentionally become a spokesperson for the issue, though I was far from an expert. At some point during the commotion, a friend at the Wildlife Conservation Society sent me an account detailing a similar event that they’d come across—only this mass collision had occurred 135 years earlier.

I was perplexed. I thought bird strikes were a modern issue, born of our love of glassy skyscrapers and bright cities. I wanted to know more about the origins and evolution of the city’s collision problem, and I figured diving into the past might also help me grapple with the emotional impact of the work and make me a better advocate.

I turned to Dustin Partridge, director of conservation and science at NYC ̽����ѡ, to understand why birds are drawn to this urban expanse in the first place. He helped me picture my lower Manhattan route as it existed centuries ago: a thick stand of hickory and chestnut trees amid a rich mix of waterways, wetlands, and upland habitats. Birds stopped to rest and refuel on their migratory journeys, which they navigated with the help of the planet’s magnetic field, as well as the moon, stars, and landscape features illuminated in the otherwise pitch-dark night. It’s just bad luck for birds that cities tend to develop in biodiversity havens. “The same things that make a landmass or an area good for people are also usually good for birds,” Partridge says. “These long-term routes are ingrained over millennia...they are not just going to stop flying along the flyway because the city is here.”

In fact, because of our lights, the modern city  a higher density of migrants today than the area did centuries ago. Scientists still don’t know exactly why artificial illumination entices and disorients birds, says Andrew Farnsworth, a migration ecologist and visiting scientist at the Cornell Lab of Ornithology, but the answer is likely buried deep in evolutionary history. What has never been a mystery is that our illuminated cities coupled with man-made structures make a fatal combination: Our bright skies draw in wild birds, and the hazards we’ve erected kill them. 

Early reports of avian collisions in North America to oil-fueled lighthouses in use well before the advent of electricity. But when Thomas Edison famously electrified lower Manhattan with incandescent bulbs in 1882, he sealed a grim fate. Four years later, the Statue of Liberty opened and began operating as the country’s first electric lighthouse. Her illuminated torch, poised 305 feet above sea level, was a beacon for passing ships and a lure for passing birds. For years, reports of disoriented birds that either collapsed from exhaustion or collided with the structure (including the mass-collision event my friend had sent me). However, “thanks to the and especially half-dazzled pilots of passing vessels,” as naturalist William Beebe later wrote, Lady Liberty’s lights were eventually adjusted some decades later and collisions subsided.  

Even as that landmark’s threat diminished, many more bright lights rose to fill the darkness as new technologies allowed architects to design taller buildings. Opened in 1931 and topped with a searchlight shortly after, the Empire State Building became the site of dramatic collisions that made with surprising frequency. Again, advocates successfully spoke out: In the late 1950s, working with the ̽����ѡ, the Empire State Building off lights during migration.

By the time planners envisioned the original World Trade Center towers in the 1960s, advances in air conditioning allowed buildings to use expansive glass designs without overheating. This design trend the problem: more illuminated buildings at night and more deadly illusions of sky and vegetation in the day. By then, wildlife groups were taking a proactive approach.

In 1967 The New York Times members of the Linnaean Society of New York, who warned that the Twin Towers would “do incalculable damage to our night-migrating birds.” Nonetheless, the soaring structures—and their 600,000 square feet of glass—opened in the 1970s and, as predicted, bird fatalities ensued.

But the Linnaean Society was wrong: The toll was in fact calculable; there just were no organized efforts to conduct the necessary surveys. At least not yet. 

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or years, Financial District worker Rebekah Creshkoff had been finding dead birds near her office. She wasn’t the only person to do so but was unique in that she couldn’t let it go. In 1997 she contacted Toronto’s Fatal Light Awareness Program Canada, which four years earlier became the first collision-prevention project in North America, and told its co-founder, Michael Mesure, that she wanted to get building managers to take action. “He had a good chuckle at my naivete,” Creshkoff recalls. Nobody was going to turn out their lights, he advised her, without evidence of the problem.

Creshkoff began surveying every morning, though she, like me, found it hard to encounter so much death. “Initially I really had to drag myself down there. I just wanted to wave a magic wand and have the issue be fixed,” she says. Creshkoff recruited a few others to help and joined forces with NYC ̽����ѡ, which has been running what became Project Safe Flight ever since. 

By 2000, their data already made a dent: Surveys pinpointed 2 World Trade Center’s most lethal area—an expanse of glass that reflected nearby trees—and building management agreed to put up barely visible fine-mesh netting along the first-floor windows. The simple intervention reduced collision deaths by about 65 percent, and in May 2001, more netting went up on other problem areas of the towers.

Though the September 11 attacks destroyed the buildings months later, the campaign’s remarkable start, marked by collaboration and momentum, went on to inform a much larger local movement. Since its early days, Project Safe Flight has marshaled more than 1,000 volunteers in total, says Jessica Wilson, NYC ̽����ѡ’s executive director. In 2014 the group also launched to crowdsource collision reports, a project that has expanded across the continent.

Armed with numbers, solutions, and volunteers spread across communities, NYC ̽����ѡ has persuaded managers and owners of a wide range of buildings and sites to alter or dim their lighting and mitigate their glass, often with the simple addition of unobtrusive grid-pattern film. Some redesigns have gone much further: Wilson points to the 2013 bird-friendly overhaul at the sprawling and especially fatal Jacob K. Javits Convention Center as a successful stand-out, one that became a model for others. As I travel around the boroughs, I am heartened by a growing patchwork of bird-deterring patterns on glass—a hotel here, a condominium building there. Downtown, my data and documentation have played a role in installing window collision film on some truly diabolical expanses.

Meanwhile, the records collected during more than 25 years of Project Safe Flight— along with those from dozens of other local monitoring and advocacy programs that now exist across the country—have been instrumental in moving solutions beyond piecemeal actions to a far larger scale. Scientists understand more than ever about what causes the greatest lethal risk. For example, while skyscrapers have historically received the most attention and may harm more birds per building, data make it clear that glass on lower levels and on lower-rise buildings and homes—especially when it reflects vegetation—takes a greater overall toll.

Today, New York City leads the nation in bird-friendly legislation. In 2019, a coalition of advocates won one of the country’s strongest ordinances, which requires that new and significantly renovated buildings use materials that reduce collision risk. “Beyond saving birds in New York City, Local Law 15 inspired similar requirements across the country and helped expand the market for bird-friendly glass, lowering prices and making it more accessible,” Wilson says. A pair of bills enacted in 2022 require city-owned and -managed buildings to turn off nonessential outdoor lights during migration and use motion sensors to minimize lights inside. A groundbreaking proposal to apply similar rules to privately owned commercial buildings by a city council member in 2023.

Beyond New York City, dozens of municipalities and states have passed a range of policies, while advocates are pushing for stronger actions at all levels, including and . From my perch, progress can’t come quickly enough. 

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n a landmark 2019 study, scientists estimated that North America had lost 3 billion birds since 1970—a nearly 30 percent decline. For many of us dedicated to picking up broken birds from sidewalks, those losses are ever-present and dispiriting. Over seven monitoring seasons since 2020, I’ve documented nearly 1,800 window-struck birds on what I call my “sad birding” roster of nearly 80 species, including many considered vulnerable and near-threatened. When I think of warblers still hitting windows that Creshkoff patrolled decades ago, I want to retire my collision backpack and move to the woods.

But to give up hope would be to give up on birds, and local advocates agree that it’s important to persevere. Window collisions are a severe issue and contribute to the loss of avian populations across North America, Partridge points out. “But I’m optimistic,” he says, “because it is something that we can relatively easily fix.” 

And it’s crucial that I not think of my monitoring in a vacuum. I’m a small link in a long chain going back more than 135 years. Through the efforts of many, the deadliest structures are being made safer. And in recent decades we’ve become even more organized in a growing grassroots movement.

Social media and the press, meanwhile, play a key role in increasing general awareness beyond dedicated bird advocates, planting seeds for further change. After my publicity in 2021, not only was I recognized by a stranger as “the dead bird lady from Twitter”—the perfect epitaph!—but it’s also not unusual for downtown residents walking kids to school to wave me down and hand over an injured bird or for community members and building workers to lament to us volunteers about dead birds they see.

Making large-scale progress may be a long game, and getting everybody on board is unfortunately complicated, but the idea of saving hundreds of thousands of birds a year in New York alone makes the tough parts worthwhile. While Manhattan will never revert to forest and wetlands, I know we can at least be better hosts to birds as they travel through, heeding the call of migration for millennia to come.

This story originally ran in the Spring 2024 issue as “Reflections of a Bird Collision Monitor.” To receive our print magazine, become a member by .