With the largest Superfund site in the country in his proverbial backyard, University of Montana Research Assistant Professor Heiko Langner knew he had a great laboratory for examining the after effects of mining on local raptor populations.
What he didn’t expect was the lack of poisons everyone was worrying about and the presence of a particularly dangerous one that no one was looking for: mercury.
Langner, along with Rob Domenech, director of local nonprofit Raptor View Research Institute, visited eight osprey nests from Deer Lodge to Missoula to band the birds for tracking and take blood samples to detect abnormal levels of common contaminants from mining operations.
The legacy left behind by the mines of Butte is one of devastation in the Clark Fork River, and the current cleanup project at the Milltown Dam has biologists and project engineers monitoring the five most prolific contaminants: arsenic, copper, zinc, lead and cadmium.
But what Langner found in the osprey wasn’t elevated levels of any of the suspects, but high – very high – levels of mercury.
“Mercury really seems to be retained in the ecosystem,” Langner said. “And it is a big deal.”
Of the test sites – two in Deer Lodge, one on the Bitterroot River near Hamilton, and the rest around the greater Missoula area – the ones downstream tested higher.
“Contrary to initial expectations mercury levels increased as we came down the watershed by a factor of four,” he said.
The two working hypotheses for the pollution increasing farther from the Butte mines are that there is simply more biota further downstream for mercury to collect in and move through the food chain or, simply, that there is more pollution near Missoula.
Osprey in the Missoula Valley also tested with higher-than-normal levels of selenium, an essential element, but one that becomes toxic at increased levels and affects birds’ reproduction.
“We’re not totally sure what all of this means,” Langner said. “There’s not a lot of reference on this.”
What they do know is that the tested birds, all about two months old and not yet flying, had significant levels of mercury and selenium, both elements not being monitored in the cleanup process at Milltown.
“We don’t know what effects this will have on life expectancy,” Langner said. “But the levels in these two-month-old birds are already at about a tenth of the level required to get mercury poisoning.”
Ospreys are easy to test because they don’t mind humans being nearby, but the small raptors are an indicator species for larger birds including golden eagles and endangered bald eagles.
Toxins from industry aren’t the only dangers these large birds face. Another study carried out by Langner and Domenech found that golden eagles suffer from high levels of lead during hunting season when they feed on the remains of kills left by hunters.
“Lead is the biggest problem for big raptors,” Langner said. “Basically if they swallow fragments left by lead ammunition, it’s a dead bird.”
Raptors are hunters but also opportunists who will take advantage of the gut piles left behind during hunting season.
“It’s impressive how consistent high levels are in eagles,” he said.
Lead poisoning from hunters’ bullets has played a large role in the demise of California Condors, and Langner said lead bullets are in the process of being outlawed in sensitive habitat areas in that state.
But his study is among the first to focus on golden eagles.
“It’s new ground,” he said. “Though we could have guessed it from what we’ve seen in other birds.”
The other studies have shown that lead levels increase in bald eagles and ravens during the hunting season and that the poisoning can extend to mice and coyotes – anything that would feast on the left-behind portions of the kill.
Humans may be at risk, too, he said. “Bullets can shed off and contaminate game meat two feet away from the canal where the bullet traveled through,” Langner said.
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