In Fredericktown, Missouri, three women walked towards what looked like a Martian landscape.
The sparsely vegetated area covered in reddish-tan dirt, once part of an active lead mine, is located in the Southwest Missouri Lead District. It contains the world’s largest lead deposits and a huge amount of tailings, waste materials that include gravel, sand, iron and various metals.
As the tailings were disposed into the environment, lead also seeped into the soil in areas where songbirds forage. Southeast Missouri State University professor Rebecka Brasso and her students are studying species that live at former and existing mining sites along the state's lead belt to find out if they're accumulating the metal.
"Let’s take you on a tour up around the site, to what we call the desert, which is a big open wasteland of mine tailings," said Brasso, an avian toxicologist. "It's not great bird habitat, but there sure are a lot of birds here."
The idea of using birds as signals for environmental health isn't a new concept. The phrase "canary in a coal mine" comes from the fact that miners used to take caged birds down into tunnels with them. When the birds stopped singing or died, that indicated that oxygen levels were low and that the miners should leave.
"If something like a songbird is accumulating lead and it's having an impact on them,” Brasso said, “then what does that mean for larger birds or mammals that live here? Who's to say that if there's an area where children are playing and they touch the soil and lick their hands, children put everything in their mouths, it's the exact same transfer mechanism [as the birds]."
Drawing blood from the birds
To measure lead contamination, Brasso's students check on nests and take blood samples from birds at six different sites in the lead district. The Fredericktown location is a part of the Madison County Mines Superfund Site, where the Environmental Protection Agency and companies responsible for the site are removing contamination.
Kathy Hixon, a master's degree student at SEMO, used a pair of binoculars to watch a bird approach one of two dozen wooden nest boxes that researchers built at the site. A piece of metal had been placed in the box to trap the bird inside. Hixson waited for that to happen, then headed to the nest box. She returned with a male bluebird in a small drawstring bag.
"When Kathy has that bird in hand, the plan is to spend as little time as you need, for the bird's sake," Brasso said.
Hixon and an undergrad student, Hannah Powell sat down across from each other. Between them are rulers, scales and supplies to draw blood from the birds. They also attached a metal band inscribed with numbers to bird's leg, so they can track that particular bird if they catch it again.
The male bluebird jostled and screeched in Hixon's hand.
"One more flinch," said Hixon, as she drew blood from one of its wings.
Declines in songbird populations
The three-year project, funded by the U.S. Department of the Interior, aims to determine if historic and current lead mining has harmed songbirds in southeast Missouri. Under the department, the U.S. Fish and Wildlife Service is responsible for enforcing the Migratory Bird Treaty Act, which mandates the protection of over 1,000 bird species, including some that SEMO researchers are studying.
"There's potential that as birds are exposed [to lead] that their populations decline. They're less healthy, less fit to survive and reproduce," said Dave Mosby, a lead environmental contaminants specialist at the U.S. Fish and Wildlife Service.
Many species of American songbirds have declined over the last several decades. Most nests fail due to natural disasters and predators consuming eggs, said Frank Thompson, a biologist at the University of Missouri-Columbia who's working on the study with Brasso.
Habitat conditions are increasingly playing a role.
"On average, only about 30 percent of nests are successful in these forested woodlands, even without lead effects," Thompson said. "So now the challenge is that we're studying birds in that context and we want to see if there are effects we can attribute to lead."
Can lead affect reproduction?
After Hixson and Powell finish taking measurements of the male bluebird, they release it back into the wild.
"So he just landed at the top of that tree," Brasso said, pointing. "He'll hang out there and be all angry at the world for a little bit."
Scientists have analyzed about a fifth of the collected blood samples. Brasso said it's already clear that bluebirds, cardinals, field sparrows and a couple other species are accumulating lead. But that's only the first step; the next is to find out whether the lead in their bodies interfere with the birds’ ability to reproduce. According to Brasso, that could be difficult to prove.
"Birds are really robust. They breed at any or all costs. They can be injured but since the goal is to survive to reproduce, even if they’re not doing well, they’ll still reproduce," Brasso said. "That's what we find in toxicology, whether it's lead, mercury, PCBs, that you can find some damages, but it takes a lot of any contaminant to push them over the edge."
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