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Eurasian Jay (Garrulus glandarius). Photo: <a href="http://www.lucnix.be/">Luc Viatour</a>, Creative Commons, some rights reserved
Eurasian Jay (Garrulus glandarius). Photo: Luc Viatour, Creative Commons, some rights reserved

Natural Selections: "Spying" jays and wren "lullabies"

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Bird songs do more just decorate the air. Dr. Curt Stager talks with Martha Foley about Eurasian jays, who "spy" on each other's sounds--for clues on where they might be able to raid a little food--and about the fairy wren that teaches chicks still in the egg a "family song," preventing imposters in the nest.

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Martha Foley: So people ask me all the time, you know we’ve been doing this show for about 25 years, if we ever run out of questions. And I say, "What, are you kidding? No way!" We’ve been talking about birds for 25 years, and yet there is new information about how birds use sound. I’m particularly struck by the blue jay story you brought in today.

Dr. Curt Stager: Yeah, it’s fun having so many scientists running around the world. Nosy scientists finding these amazing things. This is a neat one, it was in the Journal of Science in 2012, and it was studying a certain kind of jay that lives in Europe and Asia, Eurasian Jays. They like to eat nuts, and they hide their nuts for later. When they find a whole lot of them, they store them. They watch each other when they’re hiding them, and they try to steal each others’ nuts.

That was well known, that they watch each other, and so they’re careful and suspicious. This latest study was suggesting that they also listen to each other when they’re hiding this stuff. They get more clues as to where the food is by what it sounds like when one of them is burying the stuff.

They documented this by putting out these captive jays, and they put out these little trays that they could hide their nuts in. One tray had sand and one tray had gravel that sort of made a gritty grinding sound. It turned out that if they had other jays in the enclosure, they avoided the gravel tray and only tried to hide their nuts in the sand, if it was a situation where other birds could hear them and not see them. They knew that spying jays would hear which trays they put the nuts in. But when there were no other birds around they used them both equally. That showed that it wasn’t just because it’s easier to hide them in the sand.

They also showed the other side of the story. They wanted to know how do you know if a jay is listening. They said they stop making as much noise. They don’t vocalize as much when they’re listening in to see what their rivals are doing.

MF: So they’re just as sneaky on the one end as the other. That’s funny. And then there’s the wren story; wrens singing little lullabies to their little nestlings.

Female fairy wren (Malurus splendens). Photo: <a href="http://en.wikipedia.org/wiki/File:Splendid_Fairywren_female_cunnamulla.JPG">Aviceda</a>, Creative Commons, some rights reserved
Female fairy wren (Malurus splendens). Photo: Aviceda, Creative Commons, some rights reserved
CS: That is really neat. There’s this long series of research that’s been going on with this one kind of wren called a fairy wren. It’s tied in with another type of bird—the cukoos that come, and the female will lay her egg in the nest of a fairy wren, and then fly off. When the egg hatches, the fairy wren raises it with its chicks, and the cuckoo is bigger than the fairy wrens and so they chuck those babies out. They call it parasitism of the nest. There is this long ongoing story about how it’s kind of an arms race, where the wrens have little adaptations to detect and reject the cuckoo, and then the cuckoo has little adaptations to help them resist that.

This is the latest wrinkle I was able to find also in the Journal of Science. It turns out this kind of wren, the mother, sings a special lullaby to her eggs before they even hatch.

MF: Before they even hatch!

CS: But the embryos are in there and they can hear her. She sings, they call it, an incubation song that’s distinctive and it's got a little password embedded in it that’s unique to their family. So when the babies come out they use some of that sound in their calls.

MF: So she can identify them in the nest…

CS: Because they’re distinct. It’s like she comes with the worm, let’s say, and says “What’s the magic word?” And they respond the right way, you could say. She also sings this to her mate, so the mate recognizes it and also treats the babies better. Meanwhile, if there is a cuckoo in there for some reason, the cuckoo doesn’t learn that song as well as the wrens do, and so doesn’t get as much food. That’s the story for the little cuckoo.

MF: That’s the latest stage in the wren-cuckoo arms race. Thanks very much Dr. Curt Stager of Paul Smith’s College. I’m Martha Foley at St. Lawrence University.  

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