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SCOTT SIMON, HOST:

Can imagine this? You live in a big city and life is already a bit of a challenge. You know, all the people, the noise, the confusion, the unfamiliarity. Say you're trying to meet, simply communicate with a certain someone who has caught your eye. Oh yeah, wait. I should have said - and you are a songbird.

Some recent research in the journal Behavioral Ecology shows that humans may be making all that more difficult.

From member station WAMU in Washington, D.C., Sabri Ben-Achour has the story.

(SOUNDBITE OF SONG, "LOVE SONG")

SELENA GOMEZ: (Singing) I love you like love song, baby.

SABRI BEN-ACHOUR, BYLINE: Have you ever been at a bar where it was just too loud to hit on anybody?

Ooh, that's better. I said have you ever been at a bar where it was just too loud to hit on anyone?

AHARON CONERLY: Oh, all the time.

MIKEY MALIKSI: Absolutely.

VLADIMIR STANISIC: I don't go to loud places for that reason.

BEN-ACHOUR: That's Aharon Conerly, Mikey Maliksi, and Vladimir Stanisic all at various bars in D.C.

CONERLY: I mean, it's pointless.

BEN-ACHOUR: You know who feels their pain? Birds. Seriously - birds.

PETER MARRA: We know that birds are adjusting.

BEN-ACHOUR: Peter Marra is a conservation scientist at the Smithsonian Conservation Biology Institute. He says a big part of being a bird is singing and it's often to hit on other birds. And it's sometimes hard to do that because it's really, really noisy in a city.

MARRA: The sounds of trucks.

(SOUNDBITE OF TRUCKS DRIVING BY)

BEN-ACHOUR: Air conditioners.

(SOUNDBITE OF AIR CONDITIONER BLOWING)

(SOUNDBITE OF BRAKES SQUEAKING)

MARRA: Traffic in general.

BEN-ACHOUR: It's like living in a bar.

MARRA: Urban noise, those sounds compete with low frequency sounds.

BEN-ACHOUR: So birds that sing lower, like the Gray Catbird or the robin have to sing differently.

MARRA: Those low pitch sounds decline in five out of six species that we studied in urban areas. So birds have tried to change their songs to higher frequency or mid-frequency songs.

BEN-ACHOUR: Can you show me a few examples?

MARRA: Sure. So first I'll play a Carolina wren in a rural area, so where there's very low ambient noise.

(SOUNDBITE OF BIRD SINGING)

MARRA: And this is a recording of a Carolina wren at an urban site where there's a lot other background noise.

(SOUNDBITE OF BIRD SINGING)

MARRA: What you can tell is that the pitch of the song in the urban site, it's lost a lot of its low frequency sound.

BEN-ACHOUR: Here it is again.

MARRA: Rural.

(SOUNDBITE OF BIRD SINGING)

BEN-ACHOUR: Urban.

(SOUNDBITE OF BIRD SINGING)

BEN-ACHOUR: It may be hard for us to hear the distinction, but we aren't birds. Birds probably can't much tell the difference between a lame human pick-up line and a really good one either. Singing higher probably won't work for human.

(SOUNDBITE OF MUSIC)

UNIDENTIFIED FEMALE: (In high pitched voice) Hey, so do you come here often? Hello? Where are you going?

BEN-ACHOUR: But singing over the traffic isn't the only problem for birds. It turns out that big buildings distort bird songs too, especially the highest pitches.

MARRA: The buildings themselves absorb songs and refract songs and songs and sounds bounce off those buildings.

BEN-ACHOUR: Basically, higher pitches in songs like this Northern cardinal's.

(SOUNDBITE OF BIRD SINGING)

BEN-ACHOUR: ...echo in weird ways.

(SOUNDBITE OF ECHOING)

BEN-ACHOUR: And get garbled. So high pitched birds sing lower. That could work for humans.

(SOUNDBITE OF MUSIC)

UNIDENTIFIED MAN: (In low pitched voice) I'm sorry, I must be lost. You look like you might know the way back to heaven.

BEN-ACHOUR: Several of the species Marra and his colleagues looked at narrowed the range of their songs - cutting out the high parts and the low parts. So what does all this mean? Marra says we don't know yet.

MARRA: Yeah, animals are adjusting their communication. They're changing the way they speak, their accents might be changing. But to what degree is this changing, the number of young they have or how well they survive.

BEN-ACHOUR: Studies haven't looked at that question yet. But...

STEVE NOWICKI: I actually do think it could mean something for birds.

BEN-ACHOUR: Steve Nowicki studies animal communication at Duke University.

NOWICKI: Bird song is learned like human speech, and so it evolves culturally.

BEN-ACHOUR: Young songbirds learn from older ones, and so after a while you can get differences in style.

(SOUNDBITE OF SONG, "I'M A LITTLE BIT COUNTRY")

MARIE OSMOND: (Singing) I'm a little bit country.

DONNY OSMOND: (Singing) And I'm a little bit rock and roll.

NOWICKI: We know that birds can be attentive to very subtle differences in the context of choosing whom to mate with.

BEN-ACHOUR: So if birds from the city can't flirt with birds from the country anymore...

NOWICKI: Those birds are actually going to be less likely to mate with each other. I mean, literally they're going to stop being able to essentially speak the same language.

BEN-ACHOUR: Could we get a new species out of it?

NOWICKI: In the case of song, it's not yet quite so clear. But it's certainly pointing in that direction.

BEN-ACHOUR: What is clear from Peter Marra's study is that humans are loud. And for song birds that poses challenges.

MARRA: It's not just about where they nest. It's not just about where they eat. It's also about how well they can communicate in this urban concrete jungle.

BEN-ACHOUR: An urban jungle where a good pick-up line is key not just to a fun night out, but to the survival of the species.

For NPR News, I'm Sabri Ben-Achour.

(SOUNDBITE OF MUSIC)

SIMON: You're listening to WEEKEND EDITION from NPR News.

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