In the wake up reports that several bald eagles in Montana had toxic levels of mercury in their blood, a study is being launched to see if others in southeast Montana and northeast Wyoming have been affected.
Eagles with mercury poisoning showed up last winter at the Montana Raptor Conservation Center in Bozeman.
Since then, 10 to 12 more brought to the center showed elevated mercury levels and two have died.
Officials at the center said the birds came from points throughout Montana including Red Lodge, Lincoln, Fort Benton and near Dillon.
Gayle Sitter, a wildlife biologist with the Bureau of Land Management office in Billings, said the contaminated birds prompted his agency to propose a study looking at bald eagles in the Yellowstone and Powder River drainages.
"We don't have any reason to suspect it's causing any problems, but we want to get some baseline data," Sitter said.
The study, expected sometime next year, would sample the blood of young bald eagles at about 25 sites. A similar study was already planned for southwestern Montana.
Mercury occurs naturally in certain kinds of soils and rocks and also is a pollutant associated with coal-fired power plants, mines and other human-operated causes.
Once it reaches the water, mercury is usually converted to methylmercury, which fish can absorb and maintain in their tissue. When eagles, osprey or other fish-eating birds snatch them up, the poisonous mercury in the tissues comes along, too.
Montana's bald eagle population has rebounded in the last three decades. Today, there are an estimated 400 breeding pairs, compared with just 12 in 1978.
But the unexplained presence of mercury in some bald eagles has raised concerns about where it may have come from and how many others might be affected.
Sitter said the BLM decided to propose its study after news about the mercury-affected birds was reported earlier this year.
The study, scheduled to start next year, will look at a number of contaminants in bald eagles, not just mercury, he said. As oil and gas development continues, wildlife officials are hoping to have some baseline data that can be used for comparisons later.
Published on Tuesday, August 29, 2006. Last modified on 8/29/2006 at 12:23 am
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