Why Did Hundreds of Birds Die at the World Trade Center in One Morning?

Each morning, Melissa Breyer walks the streets of lower Manhattan looking for dead birds. For three seasons, she's volunteered for NYC Audubon’s Project Safe Flight as the grimmest kind of birdwatcher: she is assigned a set of buildings, and does a lap around each of them between 6 and 8AM to look for the night’s casualties.

But Tuesday morning was special in a horrific way; strewn across the pavement were hundreds of corpses of brightly colored migratory birds that were headed south on their way to their autumn hangouts before meeting their end against the exteriors of the World Trade Center complex.

“​​It was 6:15 when I got there, so the sun hadn't fully risen, but you could still see them: there were these dark little shadowy lumps of bird,” she said. “It was like a scene out of a horror film.”

In her years of volunteering during the fall migratory season, Breyer, who is the managing editor of environmental news site Treehugger, said that she’s never seen anything like it. Around just four buildings—1, 3, 4 and 7 World Trade Center, she counted 261 dead birds, including black and white warblers, American redstarts, northern parulas and ovenbirds. She brought another 30 to the Wild Bird Fund, a wildlife rehabilitation center in New York City.

In a video she posted to Twitter, Breyer walks around the World Trade Center complex in running shoes, pausing every few steps to pick up a fallen bird and place it in a large plastic bag. “Please can we turn off lights during migration???” she wrote.

Each year, it’s estimated that between 90,000 and 230,000 migratory birds are killed in New York City by colliding with building glass, a statistic made even more striking by the fact that the migratory season lasts just six weeks. And there’s indication that the number of bird-on-window collisions may be rising. According to Rita McMahon, the director of the Wild Bird Fund, the number of avian patients treated by the center has increased 20 percent from last year. 

Breyer said that a bad day for her is typically 25 or 30 dead birds, so counting over 250 on one morning was “devastating.” Though it is unclear what caused so many collisions, the proximity in time to the Tribute in Light memorial may provide a clue, as it disorients hundreds of thousands of birds annually. Kaitlyn Parkins, associate director of conservation and science at NYC Audubon, told the New York Post that the massive numbers were likely due to a "big pulse in migration" on Monday. 

There are several reasons why so many birds die each fall migration. Birds don’t understand reflections, nor can they detect clear glass as a physical barrier. Additionally, bright lights at night attract nocturnal migratory birds, potentially by disrupting their internal sense of direction. The fall migration is also a time when birds that hatched in the spring fly through the City without any of the street smarts that the seasoned adults of the spring migration possess, McMahon said. When these birds collide into skyscrapers’ windows, she added, they suffer two concussions: one when they hit the glass, and another when they fall to the ground. In short, glass buildings with their lights on at night are death traps for young migratory songbirds.

Luckily, there are easy and effective ways to prevent collisions. Myriad bird-friendly building designs for exteriors exist, such as patterning glass, covering them with shades or adding window films. In January, Local Law 15 went into effect in New York City, requiring new building projects to incorporate bird-friendly materials on at least 90 percent of their facades up to a height of 75 feet. But unless existing buildings—like those in the World Trade Center complex—are significantly renovated, the law doesn’t apply to them.

In her Twitter thread, Breyer called on the World Trade Center complex to turn off their buildings’ lights during the migration, and consider making more permanent changes to their facades. “@_WTCOfficial — lights can be turned off, windows can be treated. Please do something. @4WTC and @3wtcnewyork don’t let this be your legacy.”

Spokespeople for 4, 3, and 7 World Trade Center told the New York Post that the operator is encouraging workers to turn off lights at night and draw the blinds, while a spokesperson for One WTC said that the first 200 feet of the building are outfitted with non-reflective glass to protect birds. 

The Port Authority of New York and New Jersey, which owns the World Trade Center complex, did not respond to a request for comment.

If people come across a bird on a city street, they should pick it up: if it moves its legs, it’s not dead, rather unconscious and hypothermic, McMahon said. She recommended putting the bird in a brown paper bag for an hour, then if it begins making sounds like “tap dancing,” seeing if it flies around when released in a small, dark room. If so, people should take the bird to their nearest wildlife rehabilitation center if able, or release the bird into the wild, she added.

The most important thing that employees who work in these buildings can do is turn off the lights when they leave the office, McMahon said, adding that even one or two darkened windows can make a difference by alerting a bird to the presence of the glass. These deaths “are avoidable, or at least one can reduce the numbers substantially.”

Breyer’s Tuesday was not entirely tragic: after she took 30 injured birds to the Wild Bird Fund, McMahon’s staff got to work monitoring the birds’ concussion symptoms and feeding them mealworms. Then, on Wednesday, the rehab center released some of those same birds in Prospect Park—”so they do not have to fly through the canyons of glass facades,” McMahon said—and the birds continued on their migratory journey.