Study reveals new technique to identify individual night-flying birds for the first time

March 5, 2026

ITHACA, N.Y.— Millions of birds invisibly migrate through the night sky each autumn, most flying in near silence toward their wintering grounds. Now, scientists have developed a way to see and identify many of those birds for the first time.

In a study published today in Ornithology, researchers describe how they used thermal imaging optics, flashlights, and high-speed photography to detect and photograph birds in flight after dark. The technique allowed scientists to identify low-flying species across three fall seasons in Cape May, New Jersey—including thousands that would have gone undetected by other monitoring tools.

The method could substantially expand scientists’ understanding of nocturnal bird migration and even reveal new insights into the natural history of certain species, said ornithologist and conservation ecologist Cameron Rutt, a coauthor of the study working at the Field Museum of Natural History in Chicago.

Until now, researchers have depended on acoustic monitoring and weather radar to track nocturnal migration. Radar can detect broad movements of birds but cannot distinguish individual species and often doesn’t capture those flying low to the ground. Acoustic monitoring, meanwhile, only records birds that call while they migrate. 

“This study gives us a better idea of just how much we’re missing when we rely on acoustic monitoring,” Rutt said. “There are species that apparently don’t vocalize while migrating at night—like catbirds and flickers—and then there are birds that can vocalize, but they often don’t. This gives us a much more complete picture of what’s actually passing overhead.”

Thermal imaging—a technology that has become far more affordable and accessible in recent years—changes that equation. Because birds are warm-blooded, they radiate heat that stands out against the cold night sky. Field ornithologist Tom Johnson, a Cornell graduate and expert birder and photographer, realized this technology could be used to detect birds, briefly illuminate them, photograph them, and identify the species in flight.

Johnson began experimenting with the technique in 2019 and refined it before recruiting collaborators to deploy it on a larger scale in Cape May in 2020. There, he gathered a group of volunteers who met regularly at night to test and improve the approach—a collective they dubbed “Night Club.”

Between 2020 and 2022, members of the “Night Club” worked in teams to photograph individual migrating birds. In each team, one observer would scan the sky with a handheld thermal monocular, looking for the bright heat signature of an approaching bird. When a bird came within range, the observer would briefly illuminate it with a high-intensity flashlight—roughly as bright as a full moon at a distance. A second observer would then capture the bird using a digital camera with a super-telephoto lens, firing rapid bursts of images.

“It just feels like magic,” Rutt said, describing the first time he saw the method in practice, “like somebody flicked the light on in a room and suddenly there is a bird right next to you that you had no idea was there.”

This is the first effort to observe large numbers of nocturnally migrating birds at night and confirm their identities. Analysis of the data shows that—aside from a few highly vocal families and species—most birds pass silently over Cape May. 

Andrew Farnsworth, a coauthor and visiting scientist at the Cornell Lab of Ornithology, said the method could allow scientists to confirm social behaviors and track movements of species not generally considered to be migratory—or even known to fly at night—such as Red-bellied Woodpeckers, Downy Woodpeckers, and Northern Cardinals, which were photographed migrating during the study.

“There’s fundamental but novel natural history knowledge from a study like this, even in an era when we think we know much of what there is to know about a particular subject like migration in the northeastern U.S.,” Farnsworth said. “It goes beyond just a method that allows you to see what’s migrating at night.”

Johnson passed away three years ago at age 35, but before his death, he circulated a draft of the manuscript among collaborators. Determined to carry his vision forward, the coauthors completed the work in his honor. Farnsworth said the project reflects the many strengths that characterized Johnson’s work, who contributed more than 10,000 photos, audio recordings, and videos to the Cornell Lab over two decades. 

“This study touches so many elements of his amazing set of skills,” Farnsworth said. “That’s one more wonderful thing about the paper.” He added that Johnson intended the method to inspire others to gather new information. He foresaw that, as more people ethically adopted the approach (of utmost importance to him), the scope of our knowledge could expand considerably. 

“For lack of a better metaphor, this throws down a gauntlet for those of us following in Tom’s footsteps,” Farnsworth said, “albeit much, much farther behind him.”

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Reference 

Johnson, T. B., D. Gochfeld, M. C. Roach, G. A. Apte, R. Gallardy, S. C. Wilson, A. Marden, D. J. Irons, A. Farnsworth, and C. L. Rutt (2026). Seeing in the dark: Using thermal imaging to directly observe nocturnal migration. Ornithology 143:ukaf074.

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Media Contact

Clarissa Casper, Cornell Lab of Ornithology, (607) 254-2403, cc3224@cornell.edu

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