March 25, 2010
Bird brains? Not When It Comes To Selecting Nutritious Food
Some birds are not "bird brains" when it comes to nutrition. Scientists reported yesterday for the first time that certain birds eat berries that are high in antioxidants during their annual migration, passing up berries that are lower in these healthful substances. The behavior may help improve the birds' fitness for a long, stressful journey, they reported at the American Chemical Society (ACS) 239th National Meeting.
"We know that a diet rich in antioxidants, like those found in fruits and vegetables, is good for human health," said study leader Navindra Seeram, Ph.D. He is with the University of Rhode Island in Kingston, R.I. "As a chemist, I think it's fascinating to learn that migratory birds also seek out foods that are richest in antioxidants."Many migratory birds chow down during autumn migration, consuming larger amounts of fruits than insects than during the rest of the year. Some eat up to triple their body weight in berries per day "” the equivalent of a human scarfing more than 300 pounds of food a day. Scientists recently discovered that some migratory birds appear to prefer darkly colored, deeply pigmented fruits over other lighter-colored fruits and suggested that this preference may be related to higher antioxidant levels in the darker fruits. Until now, however, scientists had not established a solid link between fruit preferences and antioxidant levels in birds during migration.
To do so, Seeram and graduate student Jessica Bolser and colleagues collected samples of 12 common berries on the menu of migratory birds from Block Island, R.I. The tiny island is an important stopover site for migratory birds along the Atlantic Flyway. They measured levels of antioxidants and plant pigments in arrowwood, winterberry, bayberry, chokeberry, elderberry, and other berries at the peak of ripeness. Bird favored the arrowwood berries above all others, and Seeram's tests revealed that arrowwood also had the highest levels of antioxidants and plant pigments. Arrowwood fruits contained 150 percent more antioxidants than an average of all the other species combined and 650% more pigments than the other fruits, they noted.
"These results support the hypothesis that some migratory birds may actively select deeply-pigmented fruits as a signal for meals that are rich in antioxidants," Seeram said. "These disease-fighting antioxidants may help the birds combat stress and inflammation that they experience during long flights."
But the benefits are not just limited to the birds. He suggests that the findings are further evidence that fruiting-plants co-evolved with birds in a way that helps ensure the wide dispersion of plant seeds across the landscape.
"The smartest birds and the best berries seem to go hand-in-hand," Seeram said. "They need each other."
Image Caption: A hermit thrush chows down on a berry. Like other migratory birds, the thrush seems to pick the most nutritious berries, loaded with antioxidants. Credit: Ryan Brady
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