Making Bird Migration Safer

The dangers of artificial light and reflective surfaces for birds

Birds don’t see glass as a solid surface, only what it reflects or shows on the other side, like trees and sky. Almost a thousand songbirds were killed at the McCormick Center that day. Half of them were Palm and Yellow-rumped warblers, and some 40 species were found.

Though the death toll that day was extreme, bird casualties at McCormick Center are predictable. Collisions monitors have patrolled the site since 1978 and had long raised concerns about its reflective surfaces and bright lights, documenting well over 40,000 dead birds. Chicago is the deadliest city for migrating birds, according to one 2019 study, in large part due to its geography, its location on a key migratory path, and the concentration of glass there. In 2020, the city approved a bird-friendly buildings ordinance, but it unfortunately remains voluntary. Bird-friendly designs employ the use of dots, decals, or UV patterns on glass and other reflective surfaces, rendering them visible to birds.

Artificial light and glass are a one-two punch for migratory birds. Seventy percent of North America’s birds are migratory – nearly five hundred species in all – and four out of five migrate at night. Each spring and fall, billions of birds cross the night sky using a host of celestial cues as well as the earth’s electromagnetic field, low-frequency sound waves, and polarized light. But for them, that sky has changed in an evolutionary blink of an eye. One recent study found that the top 125 U.S. cities account for about 2 percent of the country’s land area but a little more than 35 percent of its total light radiance. It’s growing, too, at a rate of over 10 percent per year. That light disrupts those cues, ornithologists say, drawing birds into areas where, weakened and confused, they’re faced with lethal glass surfaces that they can’t discern as physical barriers.

What birds see are the illusion of open sky or trees – a place to fly through, a place to feed. Dr. Christine Sheppard of the American Bird Conservancy, a leading authority on preventing collisions, compares a bird flying through open space to a kid texting on a skateboard. Its attention is turned somewhere else – Is a predator approaching? Is there a food source over there? – and not the hazard up ahead.

Glass surfaces have spread across the North American landscape since the middle of the last century, and their impact on wild bird populations has been catastrophic. In 2014, scientists from Oklahoma State University, the Smithsonian Migratory Bird Center, and U.S. Fish and Wildlife Service estimated that up to almost a billion birds were killed annually in collisions in the U.S., a figure that represents as much as 10 percent of the country’s entire bird population. They used data-sets from monitors like those who collect birds at Chicago’s McCormick Center. Collisions, they found, happen mostly at buildings that individually kill a small number of birds but collectively add up to an extreme crisis: 56 percent occur at low-rise buildings, 44 percent at residences, and under one percent at high-rises. Mass fatality events such as the one at the McCormick Center or, in 2021, at the World Trade Center in New York City, garner major headlines, as they should, but the problem is any place there is glass.

Beginning to solve it requires measures targeted at a large number of structures across the country. Without national legislation, cities have been leading the way on bird-friendly building policies. A report published in 2023 by the Yale Law School’s Law, Ethics, and Animal Program found that more than 20 U.S. cities and municipalities have enacted such policies, including most recently by Washington, D.C., and the states of Maryland and Maine. But there’s still a long way to go. One necessary feature is education, and so we’d like to highlight several groups working to make things safer for bird migration, including those whose advocacy is built on the very difficult work of picking up these warm, broken bodies from city sidewalks.

Leaders in making migration safer for birds

Fatal Light Awareness Program, FLAP Canada

For the last three decades, the Toronto-based Fatal Light Awareness Program, or FLAP Canada, has led the way on highlighting light pollution and bird-building collisions. Efforts like this usually begin with one bird, and for FLAP, that bird was a Common Yellowthroat. In 1993, Michael Mesure, its executive director and one of its founders, rescued a small, yellow, black-masked warbler from a building collision and was driving it to a wildlife rehab. The bird escaped from a paper bag inside Mesure’s car, perched on the rear-view mirror, and began to sing. But as Mesure continued driving, the bird collapsed into his lap, dead. Mesure and several others then founded FLAP.

Their efforts initially focused on the nocturnal collisions caused by the bright lights of Toronto. In 1995, they partnered with World Wildlife Fund Canada on the first ever Lights Out initiative, in which building managers agreed to turn off their lights at night. Before long, their focus grew to include daytime collisions with glass, which pose an even greater risk. Migrating birds move around the landscape after they arrive on their nocturnal flights, looking for places to rest and refuel. It is during this period that they find themselves caught in a maze of deadly mirrors. In 2007, thanks to FLAP’s work, the City of Toronto adopted the world’s first bird-safe building guidelines. FLAP has since worked with commercial manufacturers on the development of bird-safe products, while dozens of volunteers continue to rescue collision victims. Since FLAP’s start, volunteers have picked up around 100,000 injured and dead birds from over 170 species. Some of the injured, though a minority of the total, have been rehabilitated at wildlife centers and returned to the wild. But perhaps the most powerful image of their work is a year-end display the organization puts together of all the dead birds their volunteers have collected over the course of that year.

Project Safe Flight and New York City Bird Alliance

In the spring of 1997, after Rebekah Creshkoff, a Central Park birder and corporate communications officer on Wall Street learned about FLAP, she began monitoring office buildings like the World Trade Center in downtown New York City. Creshkoff initially thought she’d call up building managers and ask them to turn off their lights at night. But Michael Mesure told her that would only be successful if she had the hard data to show them. She needed to find dead bodies. Creshkoff went out alone every morning that first year, in the spring and fall, biking to lower Manhattan from her uptown apartment. She found more than 400 dead or injured birds of 58 species. But it was only the beginning. The program was adopted by NYC Bird Alliance (formerly NYC Audubon), and in those early years, a few others joined Creshkoff’s endeavor, which she named Project Safe Flight. In the spring of 2001, they were able to convince management of the World Trade Center to hang nets on the worst facades of the Twin Towers, thus curbing collisions; tragically, those towers fell less than half a year later in the attacks of September 11th.

Project Safe Flight grew as volunteers moved out across the city, monitoring such iconic (and deadly) buildings as the Metropolitan Museum of Art, the Morgan General Mail Facility, and the Jacob K. Javits Convention Center. NYC Bird Alliance used those findings to pressure specific buildings into retrofitting its glass facades, none more spectacularly than the Javits Center on the west side of Manhattan. Called the Darth Vader of buildings for its dark glass and severe angles, that nickname felt all too real for those who witnessed its carnage. But in 2014, the Javits Center underwent a major retrofit of its highly reflective glass facades, led by the architectural firm FX Collaborative. Those facades were either replaced entirely with stainless-steel walls or newly coated with a ceramic dot pattern, called frit, that birds can see. An eight-acre green roof was also installed. Once one of the city’s biggest bird killers, it’s now “one of the most bird-friendly and environmentally sustainable buildings in the City,” says Dr. Dustin Partridge, NYC Bird Alliance's director of conservation and science.

The Javits Center's new bird-friendly glass has a pattern of small, opaque ceramic dots glazed to the exterior surface, rendering it visible to birds. Photo by Angie Co.

Working with deadly buildings on retrofits continues to be part of NYC Audubon’s mission. But in 2020, they and other groups in the city pushed for and won the successful passage of a bird-friendly building ordinance that was, at the time, the most comprehensive bird-friendly legislation in the U.S. All new construction in New York City, beginning in January 2021, are required to use bird-friendly materials, as well as buildings that undergo significant renovations. With all this attention, Project Safe Flight continues to grow, now with around 150 volunteers checking 50 buildings on routes in all five boroughs of the city. More than 25 years since the program’s inception, they’re needed as much as ever; in September 2021, for instance, a volunteer named Melissa Breyer found close to 300 dead songbirds, nearly all of them warblers, in a mass-collision event at the World Trade Center buildings.

Chicago Field Museum Staff and Chicago Bird Collision Monitors

The 2023 tragedy at the McCormick Center brought to light the incredible work of the collision monitors who recover thousands of birds every season in downtown Chicago, the deadliest city in America for migrating birds. What they’ve learned about those birds’ attraction to building lights dates over 40 years. In 1978, the Field Museum’s collections manager at the time, David Willard, heard an offhand remark about birds hitting the nearby McCormick Center. He went to investigate, found four or five dead birds, and continued going back with his colleagues and other Field Museum staff and volunteers every day since then, during spring and fall migration, sometimes as early as 3:30 in the morning. The dead birds go into the museum’s collections. Over 40,000 birds later, they’ve gained insights from that one building. Around 20 years ago Willard began noting which windows were illuminated each night. Several years ago, researchers from the Cornell Lab of Ornithology and the Field Museum’s scientists published a paper based on those decades of research. Using weather records and radar data, too, they found that on nights when half the windows were darkened, there were 11 times fewer collisions during spring migration and six times fewer collisions during fall migration than when those windows were lit. “The sheer strength of the link between lighting and collisions was surprising,” said Benjamin Van Doren, the paper’s lead author. “It speaks to the exciting potential to save birds simply by reducing light pollution.”

Witnessing that fatal attraction of light was how Chicago Bird Collisions Monitors (CBCM) began in 2002. That year, Robbie Hunsinger, a classical musician, and attorney Ken Wysocki noticed the circling of birds around city lights on nights of heavy migration in downtown Chicago. They committed themselves to finding the victims on the city streets; the next year, Hunsinger founded CBCM and she and a small group of volunteers began regularly checking the Chicago Loop each morning. Working with building owners and managers, they were able to help get Chicago to become the first U.S. city to have its skyline go dark during migration in the spring of 2004.

More than 100 volunteers now patrol the city during migration. Their findings continue to raise awareness to the problem in Chicago. Though public support grows, the city remains stubbornly opposed: this spring, the Chicago Department of Planning and Development decided not to make bird protection mandatory in a draft of its sustainable development policy. Disappointing though that is, there was another piece of news that provided encouragement: the McCormick Center is reportedly about to have feather-friendly material installed on all its glass.

Northern Flicker, killed at 7 World Trade Center, NYC, September 19, 2021. Photo by Melissa Breyer.

What you can do to help make migration safer for birds

1. Get involved with local bird advocacy and conservation groups, or start one yourself

Whether you live in these cities or not, you can support these groups or ones like them doing similar work in your area. Find out if your town or city has a bird-friendly building ordinance and if they don’t, look into whether there are groups lobbying for them, such as your local bird conservation organization.

2. Make your home bird-safe

You can easily make your home bird-safe and you don’t even need to impair your view to save birds; check out what the collisions experts at the American Bird Conservancy have to say on what you can do.