High Levels of Mercury Found in Vt. Birds
BURLINGTON, Vt. Scientists have found high levels of mercury in songbirds on Vermont mountaintops. Researchers at the Vermont Institute of Natural Science announced this week that mercury was found in the blood and feathers of the rarely seen Bicknell's thrush on Mount Mansfield and Stratton Mountain.
In some birds, the level of mercury was high enough to harm their ability to reproduce, conservation biologist Kent McFarland said Wednesday.
The findings were unexpected, but matched evidence VINS and Canadian researchers gathered from high-mountain birds in other parts of northeastern North America. Until now, mercury was thought to be a threat primarily to fish and fish-eating birds -- and to humans who eat too much mercury-contaminated fish.
"Biochemists had predicted we wouldn't find much mercury in the birds, and that it wouldn't be methylmercury," the form toxic to humans and animals, McFarland said.
Instead, sampling by McFarland and fellow biologist Chris Rimmer not only found mercury in the birds' blood, but all of it in the form of methylmercury.
Wind carries mercury from the smokestacks of industrial and power plants into New England, where it falls with rain and snow onto the land and water. Bacteria convert elemental mercury into the more toxic methylmercury.
The biologists' findings were one part of a multi-year, government-financed study that found greater and more pervasive mercury contamination than previously known across the Northeast.
Over five years, the researchers tested 200 birds, including Bicknell's thrush, two high-mountain warblers and the white-throated sparrow. Levels were higher at Stratton Mountain, where mercury deposition also is higher, McFarland said.
McFarland said researchers suspect that mercury is taken up by high-elevation trees. Moth caterpillars eat the leaves, and Bicknell's thrush dines on the caterpillars.
The songbird is a 6-inch, migratory insect-eater that nests in high-elevation northeastern forests in the summer and winters on islands in the Caribbean.
Although it is not an endangered species, Vermont considers the bird of "special concern" and has imposed strict conditions on ski area development near the bird's habitat.
"Mercury may already be having an insidious effect on the bird," McFarland said. "This is also a wake-up call for us as a species to reflect on how much mercury we are putting in the atmosphere. There's mercury all over the place. The thrush may be a canary in the coal mine."
Source: Associated Press