JUANA SUMMERS, HOST:
Listen up. Do you know what this bird is?
(SOUNDBITE OF SWAINSON'S THRUSH CALL)
ADRIAN WOLF: The Swainson's thrush. It's a lovely, ethereal sound.
(SOUNDBITE OF SWAINSON'S THRUSH CALL)
WOLF: Yeah, it's beautiful.
SUMMERS: Adrian Wolf knows birds. He once studied a threatened species called the streaked horned lark for over 10 years.
WOLF: It has a piece in my heart, and it's little nestlings look like grumpy old men.
MARY LOUISE KELLY, HOST:
Adrian Wolf is not studying just one bird, not anymore. He manages forests in western Washington state. He is stewardship director for the Great Peninsula Conservancy, and he relies on bird sounds to measure his work. He thinks of it like the birds are leaving reviews.
WOLF: This habitat is good. I'm going to keep coming back here, and I'm going to keep reading. That's the best yelp review you can have is you come back.
SUMMERS: More bird calls can mean more birds are moving into the forest, and that is important because Wolf says birds, in general, they're struggling.
WOLF: They're having a hard time. Yeah, we've lost about 3 billion birds since 1970. And in the western forests alone, we've lost about a billion birds.
SUMMERS: That has to do with a lot of factors, but a big one is habitat loss. So Wolf often works to thin out former timber forests and introduce diverse plant life.
KELLY: And that is where Avian Yelp comes in. Wolf and the Great Peninsula Conservancy started a pilot program back in 2022 to attach small audio recorders to trees. This was with a grant from the Cornell Lab of Ornithology. The program has since expanded to 100 sites across Washington state. It's partnered with other land trusts and tribes and is now called the Listen Up Collaborative.
SUMMERS: Wolf is listening for 45 target species, like the chestnut-backed chickadee...
(SOUNDBITE OF CHESTNUT-BACKED CHICKADEE CALL)
SUMMERS: ...The pileated woodpecker...
(SOUNDBITE OF PILEATED WOODPECKER CALL)
SUMMERS: ...The Pacific wren...
(SOUNDBITE OF PACIFIC WREN CALL)
SUMMERS: ...Or the spotted towhee.
(SOUNDBITE OF SPOTTED TOWHEE CALL)
KELLY: To be clear, those recordings came from the Cornell Lab of Ornithology. But the audio devices in Washington have captured more than 400,000 recordings of bird songs and calls. To sift through these sounds, the group uses an AI program.
WOLF: And then we can look at that data and see the frequency and the duration of these birds singing. And you make some assumptions that the more birds that are singing or the more species that you hear, that that habitat is favorable.
SUMMERS: And remember that ethereal-sounding bird? Wolf said that the Swainson's thrush has been leaving positive reviews. Its songs have shown up more often on recording since 2022.
WOLF: We have found a positive response, as we've thinned the forest and opened up the stands a bit.
KELLY: Wolf says this work will continue for years. So he will be listening for many more yelp reviews that perhaps you've just called them tweets. Transcript provided by NPR, Copyright NPR.
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