URI senior Martina Mller of Kingston, working in cooperation with Associate Professor Scott McWilliams, Ph.D. candidate David Podlesak and colleagues at the University of Wisconsin, studied the food preferences exhibited by black-capped chickadees.

"When plants are grown in conditions of higher carbon dioxide, they produce increased levels of several secondary compounds -- tannins and phenolics -- that they use to defend against herbivory," said the 23-year-old wildlife conservation and biology major. "Those secondary compounds are absorbed by gypsy moth caterpillars that feed on the plant's leaves, which other researchers have found reduces the caterpillar's growth rates. We wanted to see if the chickadees can detect the secondary compounds in the caterpillars and if they have preferences for caterpillars that fed on different types of leaves."

Using chickadees captured in Kingston and acclimated for three days, Mller and McWilliams fed the birds a choice of caterpillars that were high in tannins or phenolics and other caterpillars low in those compounds.

"It was clear that the birds could tell the difference between the different caterpillars and they had strong preferences," Mller said. "They're intelligent birds with a keen capacity to learn."

While the birds showed a distinct preference for caterpillars low in tannins and phenolics, they also showed a preference for foods they had eaten previously. "Previous experience does affect their preferences," Mller said.

So what does all this mean? According to McWilliams, it could mean a great deal in a world that is growing warmer due to increasing levels of carbon dioxide in the atmosphere
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Contact: Todd McLeish
tmcleish@uri.edu
401-874-7892
University of Rhode Island
26-Jan-2004