Just after dawn in Washington, D.C., Stephanie Haley is walking a familiar downtown route, scanning the sidewalk next to office buildings. There, huddled on the ground, is a motionless olive-green songbird. It's an Acadian flycatcher, no doubt on its way to Central or South America before it slammed into a window.
Haley quietly sidles up to it, gently placing a net over the bird. Then she picks the bird up, using a gloved hand. It begins peeping in dismay.
"This is a good sign, the fluttering, which means that hopefully he's just stunned," says Haley, who volunteers with a local group called Lights Out DC, which urges people to turn off artificial lights during migration season, because these lights can attract birds and lead to deadly collisions.
"I'll take him to City Wildlife and the doctors will check him out," she says, referring to the local wildlife rescue nonprofit which organizes and runs Lights Out DC.
But even though the vets put this bird in an oxygen chamber, it eventually succumbs to its injuries. Most collision victims do, even if they initially fly away. They can have concussions, and broken bones.
"They can be flying up to 30 miles per hour when they hit the glass, so it's a very loud thunk," says Lisbeth Fuisz, another volunteer.
The latest estimates suggest that, every year in the United States, collisions with windows kill a billion birds.
Other than cats and habitat loss, glass is the biggest danger birds face. But research and testing has shown what kinds of glass and window treatments really work to prevent collisions, says Bryan Lenz, with the American Bird Conservancy.
The trouble is, the advocates for the birds, like the birds themselves, are having to grapple with a landscape that is just covered with ubiquitous glass.
"It is becoming now a question of, how do we do it at a scale big enough," says Lenz, "to save a billion birds."
Transparent or reflective
Each night during migration season, hundreds of millions of birds take to the skies, flying through the night to take advantage of the evening's cool, stable air. They navigate with the help of the moon and the stars, and come down in the morning to rest. That's when they can encounter glass.
Evolution hasn't prepared birds to deal with glass. If it's transparent, they think they can fly through it. If it's reflective, they can mistake the reflections for real trees and sky.
Most collisions don't happen way up high. Instead, they typically occur close to the ground, below the treeline. So window collisions aren't just confined to cities. But cities tend to be where people go out looking for birds, trying to find them before the rats get them, or before custodians sweep them away.
In DC, the data collected over the years by volunteers makes it clear that about a half-dozen buildings account for a large share of the deaths. Clearly, their architectural features confound the birds, turning the buildings into death traps where volunteers find corpses again and again.
"This is a problematic building," says Fuisz, walking up to one office complex on North Capitol street. It wraps around a plaza with trees, and has two sections that converge on a glass atrium, effectively funneling birds towards a multi-story wall of glass.
"Do you see how the reflection works?" says Fuisz. "It looks like you could keep going."
On top of the building's entrance, a revolving door, she spots a small dead bird. It's a female yellowthroat that fell there after hitting the glass wall. "That's a pretty common window collision victim," she says, carefully recording the death.
Similar data collection efforts have been going on across the country, in places like Chicago, Philadelphia, Dallas, and San Diego. The goal is to reveal the scale of a problem that's mostly invisible — unless something dramatic happens.
A thousand birds
On the night of October 4, 2023, hundreds of migrating birds slammed into McCormick Place Convention Center in Chicago, a large building in one of the major migratory fly-ways that's floor-to-ceiling glass, right on the edge of Lake Michigan. This made headlines nationwide.
"People who never even thought about birds were suddenly like, 'Wait a minute, a thousand birds died in one night crashing into one building?'" says Tina Phillips, with the Cornell Lab of Ornithology
This incident became something of a watershed. It inspired the U.S. Fish and Wildlife Service to convene a summit. Attendees included people from birding groups, government agencies, architecture firms, research universities, and dark sky groups that want to minimize artificial light.
Phillips says they'd all been trying to prevent birds from hitting buildings, but separately.
"And so coming out of that meeting," she says, "we knew we had to keep working together to really try to make this impact meaningful."
They formed the Bird Collision Prevention Alliance, and more than a hundred organizations have now joined, including federal agencies. They're sharing resources and ideas, and have working groups that meet frequently.
This comes as the Trump administration has weakened federal protections for migratory birds, exempting companies from being responsible for birds killed accidentally. But members of the new alliance say their group isn't about pushing policy at the national level.
"We're just focusing on the science and we're focusing on the best way to save birds at scale," says Lenz, "without getting bogged down in political conversations."
He says in the past, people didn't know how to keep birds away from glass: "People used to say, 'Put a hawk decal on your window and that's good because the birds will be scared of that.' The only thing that does is keep the bird from hitting the hawk decal."
To understand how well modern solutions can work, consider the Chicago convention center where so many birds died in 2023. Staffers and researchers had been monitoring bird deaths there for some time, says chief operating officer and interim general manager Patrick Allen.
"We were a big piece of glass sitting right out on the lake," he says. "There's no doubt the reflections would attract the birds."
After the high-profile mass collision, he says they decided to put an easy-to-install product on all of the windows. "It's just nothing but a film with dots in a particular pattern," he says. "You put it on the window, and you pull it off and the dots stay on."
Data collected before and after this treatment showed that it reduced bird collisions by 95 percent.
"The numbers are awesome. We're very proud of it," says Allen, describing it as a "win-win" for both the convention center management and the birds.
The fix cost over a million dollars, but Allen says that's only because they had a huge expanse of glass — enough to cover two football fields. And costs can come down if a building or major renovations are planned to be bird-friendly from the start.
That's the case that wildlife advocates in Dallas are currently making, as that city is planning to substantially upgrade its Kay Bailey Hutchison Convention Center.
The convention center has been the top killer of birds in downtown Dallas among the 129 buildings that volunteers have monitored in the last few years, says Mei Ling Liu, community conservation director with the Texas Conservation Alliance. She says the center has accounted for 31% of the bird deaths they've logged.
Her group is trying to get support for the new renovations to be done in a bird-friendly way. What's more,"we're hoping to really use the case of the convention center to start having the conversations with other building managers," she says, saying that Dallas remains very bright at night during the migration season.
Fixing it at home
Only a few major cities in the U.S. have buildings requiring new construction or significant renovations to be done with bird-friendly materials — DC is one of them.
And the data collected by volunteers in DC has convinced some building managers to make changes, like turning off lights and putting treatments on some windows.
"You would think that most buildings would care and want to fix the problem," says Stephanie Dalke, another volunteer with Lights Out DC. "It turns out, it can be complicated and expensive to treat a commercial building."
That's why she thinks it's important for homeowners to know what they can do. The cumulative effect of houses is large, because there's so many, but the amount of glass that needs to be treated at each one is small.
The Bird Collision Prevention Alliance, for example, says a start could be treating home windows that have been known to have had a bird collision in the past, or windows that are near attractive features like birdfeeders or fruit trees.
Dalke's monitoring path through DC takes her under a skyway that connects two buildings downtown. It's made of mirrored glass.
"We call this the walkway of death," she says. "This is a very deadly spot."
There on the ground is a dead ruby-throated hummingbird. It's tiny, the size of her thumb, with iridescent green feathers. It was on its way to Central America.
"It boggles the mind that these guys can fly over the Gulf of Mexico," she says. "I mean, how can they do that? It's just amazing. But then we take them out, with some glass."
She carefully notes the location and date, so this bird can go into the volunteer group's database. She takes a photo. Her cell phone is filled with hundreds of pictures of window collision victims. And then she keeps walking, looking for more — and hoping not to find them.
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