Emerging Science Note/Global Warming Diet

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CURWOOD: Coming up, hear more from Michael Pollan about the differences between feedlot and grass-fed cattle as we head out on the range. First this note on emerging science from Cynthia Graber.
GRABER: If global warming continues as predicted, songbirds might have to change their diet. It's already known that when plants are exposed to an increase in carbon dioxide, they in turn increase certain chemicals in the leaves, known as tannins and phenolics. Caterpillars that munch these leaves have a higher level of the chemicals in their bodies.
But scientists at the University of Rhode Island realized no one had taken this research one level up the food chain to look at how this might affect the birds that eat those insects. So the team got a hold of gypsy moth caterpillars from a test forest that was being sprayed with higher levels of carbon dioxide.
These caterpillars became food for a group of black-capped chickadees.
Another group of birds was fed caterpillars with normal, low levels of tannins and phenolics. Then the groups were given their choice of which type of caterpillars to eat.
Turns out, the birds clearly preferred caterpillars with lower levels of the chemicals.
Researchers say this indicates that birds in a warmer world might end up with an aversion to gypsy moths  ? which could then lead to an explosion of the moths, causing widespread defoliation. That's this week's note on emerging science, I'm Cynthia Graber.
CURWOOD: And you're listening to Living on Earth.
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[MUSIC: Badly Drawn Boy "Delta (Little Boy Blues)" ABOUT A BOY SOUNDTRACK (BMG Artist Direct - 2002)]