This time of year, the call of loons on Swain’s Lake and Mendum’s Pond in Barrington, N.H., has been replaced by silence – and soon, the whine of snowmobiles.

The ponds, lined with summer cottages and known for their bass fishing, are like dozens – even hundreds – around New Hampshire. But over the last eight years, they’ve produced loon eggs with the highest mercury levels of any tested in the country.

Now, a scientist who studies those eggs is citing them as evidence the Bush administration is headed down the wrong path with the mercury pollution plan it announced last week. David Evers, executive director of the BioDiversity Research Institute in Falmouth, Maine, says changes in mercury levels in the eggs suggests that mercury pollution stays close to its source, generally incinerators, coal-burning power plants and even home furnaces.

The solution, he says, is to require plants to use the best available technology to cut emissions.

The administration has a different approach. Last week, it proposed regulating mercury polluters by allowing them to buy pollution credits from cleaner plants.

After six years, the plan would start imposing limits on mercury emissions, though environmentalists note the limits are lower than those proposed by the Clinton administration and some would not take effect until 2018.

The Environmental Protection Agency says the program would cut mercury emissions from coal plants from 48 tons a year to about 34 tons a year. And when all the limits were imposed, emissions would drop to about 15 tons a year, the EPA says.

“We are calling for the largest single industry investment in any clean air program in U.S history,” EPA Administrator Mike Leavitt said.

But Evers says credits trading is the wrong approach for a pollutant that stays close to home.

“You end up sacrificing parts of the country like southeastern New Hampshire to try to improve mercury pollution nationally,” Evers said.

The starting point for his argument is a study he co-wrote that was published this year in the journal Ecotoxicology. The study found that loon eggs in southeastern New Hampshire had the highest mercury levels of any tested in eight states, and that levels in Swain’s Lake and Mendum’s Pond were especially high.

But the study was based on eggs tested before 2000. More recently, eggs from the same ponds have shown a significant decline in mercury, apparently because of state-mandated changes at municipal waste incinerators in the area, Evers said.

Across New England, about 40 percent of mercury pollution comes from New England sources, 40 percent from the Midwest and 20 percent from global sources, as far away as China, scientists say.

But in hot spots like southeastern New Hampshire, an even larger proportion of the mercury originates locally, Evers said. His study found the highest levels in the area roughly east of Interstate 93 as far north as Concord.