By Kim Rendfeld
CARBONDALE, Ill. – Birds that are active during the day sing later into the night in places with significant light pollution, according to research by a Southern Illinois University Carbondale professor and his colleague.
Brent Pease, an assistant professor in SIU's School of Forestry and Horticulture, and Neil Gilbert, an assistant professor in the Department of Biology at Oklahoma State University, analyzed data gathered from around the world, comparing more than 180 million bird vocalizations in a single year with global satellite imagery.
"We were shocked by our findings: Under the brightest night skies, a bird's day is extended by nearly an hour," Pease said.
Pease and Gilbert's paper, "Light pollution prolongs avian activity," was published today (Aug. 21) in Science magazine.
The project came about in his effort to excite undergraduates about birds. Two years ago, Pease installed a computer with an attached microphone at Touch of Nature Outdoor Education Center to broadcast birdsong in the main campus' Agriculture Building eight miles north, where his department and others are housed.
What resulted was a basic data dashboard on the Ag Buildings' monitors.
Then, Pease employed BirdWeather, which makes sophisticated recording devices with Wi-Fi, GPS and sensors connected to the BirdNET database and its machine learning from the Cornell Lab of Ornithology and the Chemnitz University of Technology. BirdWeather's dashboard provided a better visualization of what bird species were in the area.
"We started seeing — in real time — which birds were at Touch of Nature, right in our Agriculture Building," he said. "I realized that I stumbled upon something really important for wildlife research. All of a sudden, we not only know where species are but how they are behaving 24/7.
"For decades, we have been steadily improving our ability to predict where species are and how many individuals there are. But BirdWeather unlocked behavioral research at large geographic and time scales. We could start to learn — at a scale never before — how birds were responding behaviorally to human forces."
As trail cameras had revealed around-the-clock mammal behavior about 25 years ago, BirdWeather, along with BirdNET, could now do for birds.
"We are just now entering the golden age of avian conservation, all through machine learning and participatory science," said Pease, who has led several citizen-science projects to assess wildlife on the SIU campus and to record sounds of nature during the April 8, 2024, eclipse.
With BirdNET, Pease and Gilbert used machine learning to convert bird vocalizations to visualizations called spectrograms, with a distinct visual pattern for each bird species. BirdNET then cross-checked the pattern with spectrograms of more than 6,000 species in its database.
"The machine learning algorithm makes it possible to analyze 24/7 audio recordings, which would otherwise take lifetimes to listen to," Pease said. "Neil and I are the first, to our knowledge, to apply and analyze the BirdWeather data in this way. We have many research options, but first we focused on how birds are responding to global light pollution, which is a growing concern for humans and wildlife alike."
Pease noted that birds staying up an hour past their normal bedtimes was an average. Actual times varied by species.
"The next question was: why?" Pease said. "What is driving this response by birds? We had the idea that maybe it was a species' photoreceptor sensitivity – their eyesight. And this turned out to be a key factor. Species with large eyes relative to their body size had a disproportionately stronger response to artificial light at night. They were more sensitive to light at night than species with small eyes."
The final question – is the impact positive, negative or neutral – will require further study. Birds might have more time to forage for food and to mate, but an hour less sleep could be detrimental to their health.
"This is citizen-science at its best," Pease said. "A technology designed for people to check out the species in their own backyards has acquired an unprecedented amount of data since 2021 – over 1.4 billion vocalizations from more than 11,000 locations across the globe. Neil and I are determined to continue to apply the technology for wildlife conservation."
Tim Crosby contributed to this story.
