On a morning in late September, Kestin Thomas stood next to the towering glass facade of the Time Warner building in Manhattan holding a dead bird. The small body was still warm in his hand, but he couldn’t feel the flutter of a heartbeat or the soft puff of breath escaping. He recorded the death on a data sheet, marking the time, day, and location. Then he put the bird in a plastic bag and took it home, leaving it in the freezer for a day before finally dropping the body off at the New York City Audubon Society.
“It was heartbreaking,” he says.
Thomas is one of many people who took up birding during the pandemic, inspired by the sparrows he saw on his daily walks. “I realized how adorable they are and that they’re living in the city amongst us and thriving,” he says. He started taking pictures and sound recordings, identifying the birds with the help of apps like Merlin and eBird. Those entries add information to databases that scientists use to study migration and behavior. “All of those observations that people are submitting, they go into very advanced modeling to create distribution maps for species, to look at trends of their populations,” says Andrew Farnsworth, a senior research associate at the Cornell Lab of Ornithology which maintains both apps.
Now Thomas is also a volunteer with the Audubon Society’s Project Safe Flight, which is collecting a different kind of data. The group enlists people to monitor New York City buildings during the fall and spring migration seasons to record the number of birds killed or injured by flying into windows.
Bird-watching has boomed during the pandemic, and all that extra interest has translated into citizen science initiatives seeing a huge swell in participation. With the fall migration now in full swing, this army of avid birders is amassing a wealth of data about how weather, human movements, artificial lights, and city infrastructure can affect birds as they travel. Farnsworth notes that while both Cornell projects have grown every year since their inception over a decade ago, the increase in users, downloads, and data over the past 18 months was unprecedented. “Pandemic time was really off the charts,” he says.
eBird, which allows birders to note which species they’ve spotted—and where—had a more than 40 percent increase in sightings in April 2020 over the previous year. That’s more than double the app’s normal annual growth, according to data provided by Farnsworth. This February, 140,000 users logged on, to date the greatest number of users in a single month and a 50 percent increase over last February. Now, there are over a billion entries.
The same is true for Merlin, which helps birders make identifications through pictures, audio recordings, or descriptions of the bird’s color, size, and location. This February, the app was installed on 200,000 new devices—a 175 percent increase over the previous year—and it had more than 611,000 active users, double the number recorded in February 2020.
eBird was already an immensely useful database that scientists have used to study the bald eagle population, examine the effect of extreme weather on birds, and show changes in species’ songs. Now pandemic-era entries are helping them understand how human activity—or the lack thereof—affects birds. One study published this month in Science Advances by researchers at the University of Manitoba used eBird data from the United States and Canada to examine bird behavior in areas that normally have lots of people, like cities, airports, and major roads. The researchers reported that during lockdown, bird activity increased for more than 80 percent of the species they studied, including hummingbirds, bald eagles, and barn swallows.
Farnsworth says this citizen data is crucial. Scientists can monitor migration using weather surveillance radar, and they’re experimenting with acoustic sensing that uses microphones to record bird calls. (Machine learning can identify which species are migrating, based on the captured songs.) But there are still no devices that can replace in-person observation. “We actually really want humans involved,” he says. “Going out and using your ears and eyes, and your own sensory abilities—we want people doing that because it engenders a much, much closer relationship with what’s happening around you.”
But this flood of new data presents a conundrum: Scientists can’t always tell whether changes in the data are due to animal behavior or just an increase in the amount of information available. Take the data about how many birds are injured or die after flying into buildings. Twice a year, millions of songbirds, raptors, hummingbirds, and shorebirds travel through New York City along the Atlantic Flyway, from their summer homes in Canada and the northeast to their winter habitats in Florida and the Caribbean. They can get disoriented by bright lights or by window glass, which they often can’t perceive as a barrier. Last year, the count of dead and injured birds in New York rose precipitously during the fall—but so did the number of bird-watchers.
That fall, volunteers for Project Safe Flight found 403 dead or injured birds, nearly quadruple the number they found in 2019. Concerned citizens also brought hundreds of stunned, concussed, and injured birds to the Wild Bird Fund, a rehabilitation center in Manhattan. Similarly, reports on dBird, a crowdsourced database where anyone can record birds they find dead or injured following building collisions, more than doubled, from 850 in 2019 to over 2,200 in 2020.
And this year, a Project Safe Flight volunteer went viral when she tweeted pictures of the more than 200 dead birds she found in just one hour while patrolling outside two buildings at the World Trade Center complex, hundreds more than she usually sees. Her plea for people to turn off the lights to avoid attracting birds turned into a public outcry that received national media attention.
“It’s really difficult to see if things have changed or if additional interest in the programs have led to changes in the data,” says Kaitlyn Parkins, associate director of conservation and science at NYC Audubon. She suspects reports are up because more people are paying attention; this year Project Safe Flight has 40 people patrolling buildings in the city, the most to ever participate in the project.
But Farnsworth notes that it’s also possible that, while there are more concerned birders, there are fewer humans in New York City in general: less urban foot traffic, possibly reduced building maintenance. And that might mean there have been more opportunities for predator rodents and cats to make off with birds’ bodies, meaning the count is actually artificially low.
“It’s all sorts of interesting, confounding variables,” says Farnsworth. (For his part, he suspects that only human behavior—not something inherent to the birds or the buildings—can explain the trend: People are active in different areas, and they’ve started noticing the dead birds more.)
And, if that’s not complicated enough, data about bird migration and population is also being affected by this participation boom. It’s not just that more people are observing—it’s also a matter of where they are observing. Studies in Colombia, Portugal and Spain, and the US that examined citizen science projects like eBird and iNaturalist found that observations in urban areas increased as people stayed home, while sightings in more remote habitats may have been undersampled because fewer people were traveling to those destinations. These reports suggest pandemic-era changes in citizen science are so great that they must be factored into future research that makes use of this data.
Despite all these complex factors, the data collected under these unusual pandemic conditions can still be useful. This year, Project Safe Flight’s data will help a graduate student at Columbia University research the effect of weather patterns on the likelihood of bird-building collisions.
And enough data can lead to real change. Prior Project Safe Flight data documenting the harm glass buildings pose to birds helped lead to the 2019 passage of Local Law 15, which requires new construction in New York City to use bird-friendly design, including glass patterned with dots that help them avoid the windows. Parkins says that volunteers monitoring the Javits Convention Center in Manhattan collected data showing a 90 percent decrease in collisions after the building was renovated to include such features.
For Kestin Thomas, pandemic birding has felt like an entree into a secret world. Now, even when he’s not on duty for NYC Audubon, he always takes plastic gloves and bags with him in case he finds a distressed bird that can still be saved. On the same day that he found the dead bird, he also happened across a common yellow throat that seemed stunned after flying into a window. He took it to the Wild Bird Fund, and a few days later, he got an update: After being treated with pain medication and anti-inflammatories, the bird was once again on his journey south. “Thank you for rescuing this bird and having the compassion to bring him to us,” the email read. “He would not have survived in the wild without your help.”
Thomas will continue his patrol until migration season ends in November, and he encourages others to keep an eye out for injured or concussed birds and consider taking them to a wildlife hospital. “Start looking at the ground more and watching where you’re walking,” he says. “They’re so easy to miss.” At the very least, he advises people to move them out of the way so they don’t get run over by cars, bikes, or scooters. Thomas says it can be sad and even a little bit scary to pick up a wild bird. “But once you go for it, it’s the best feeling in the world to help a living creature, a wild animal,” he says. “They feel so magical in your hand.”