MARY LOUISE KELLY, HOST:
Allegedly, the early bird gets the worm. But now it looks like a lot of birds are starting their days earlier than ever. That is one of the findings of a sweeping new study of bird activity around the globe. NPR's Nell Greenfieldboyce reports on how scientists manage to track the daily doings of hundreds of species.
NELL GREENFIELDBOYCE, BYLINE: It used to be if you wanted to know what birds were up to, you'd have to go out in the field with binoculars.
(SOUNDBITE OF VILLAGE WEAVER CALL)
GREENFIELDBOYCE: Increasingly, though, bird lovers are relying on audio recordings like this one. That's a village weaver.
(SOUNDBITE OF NORTHERN FLICKER CALL)
GREENFIELDBOYCE: And that's a Northern flicker. These recordings were made by a project called BirdWeather. It sells little plastic devices that people can mount outside their homes. These devices have microphones to pick up bird calls and the computing power to identify the species in real time. Lots of people have installed these things.
BRENT PEASE: They're like, hey, I like birds, kind of. I like to feed birds. What's in my backyard?
GREENFIELDBOYCE: That's Brent Pease, a wildlife researcher with Southern Illinois University. What interested him was that BirdWeather has been collecting and storing all that audio from thousands of sites on multiple continents.
PEASE: Really, I would say largely, the wildlife science community doesn't even know this dataset exists. And here, we literally have over a billion bird vocalization detections on the BirdWeather platform since 2021 that tell us in real time how birds are behaving.
GREENFIELDBOYCE: He says this really just blew his mind.
PEASE: And I kept thinking about this dataset, and I kept thinking about this dataset.
GREENFIELDBOYCE: He wanted to use it in some way. So he turned to a colleague, Neil Gilbert at Oklahoma State University. Gilbert says he thought, well, what about light pollution? He knew of some research showing it affects certain birds, so he suggested...
NEIL GILBERT: You know, I think we can try to estimate light pollution effects for a whole bunch of species.
GREENFIELDBOYCE: That's just what they did. They combined bird data with satellite data on light pollution, plus sunrise and sunset times. Gilbert says their analysis shows that unnaturally bright skies can really change the lives of birds.
GILBERT: These birds - effectively, their day is almost an hour longer. They start vocalizing about 20 minutes earlier in the morning. And they stop vocalizing about, you know, 30 minutes later in the evening.
GREENFIELDBOYCE: That's an average effect over hundreds of species. Some birds show much bigger responses.
GILBERT: American robins will sometimes be singing, you know, 2 hours before sunrise in some of these light-polluted areas.
GREENFIELDBOYCE: And some species seem less influenced. For example, birds with small eyes, like the tufted titmouse, don't react much to artificial light; neither do birds that roost in dark, enclosed nests or tree cavities. The findings appear in the journal Science. Jeff Buehler is with the University of Delaware. He's researched light pollution in birds and says the scope of this study is unprecedented.
JEFF BUEHLER: Compared to what has been done in the past. A much smaller-scale study is only looking at a handful of species at a time.
GREENFIELDBOYCE: What's not clear, though, is whether a longer day is good or bad for the birds. Maybe it means they get more time to forage for food, or maybe it interferes with their sleep. To understand all that, scientists would need to study individual species much more closely than just recording their calls.
Nell Greenfieldboyce, NPR News.
Copyright © 2025 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.
Accuracy and availability of NPR transcripts may vary. Transcript text may be revised to correct errors or match updates to audio. Audio on npr.org may be edited after its original broadcast or publication. The authoritative record of NPR’s programming is the audio record.