High levels of mercury found in Alaska’s Arctic shorebirds

Coupled with threats such as habitat destruction and climate change in Alaska’s Arctic, high levels of mercury discovered recently in shorebirds could create further challenges for the species.

In a study published in The Condor: Ornithological Applications, lead author and TWS member Marie Perkins, a Ph.D. student at McGill University, looked at mercury levels in the shorebirds’ blood and feathers. The study, which was conducted during the breeding season as well as post-breeding staging when they began their southward migration, focused on birds in Barrow, Alaska, on Alaska’s North Slope.

“What we found was some shorebirds, particularly in the Barrow area, have mercury concentrations high enough to cause detrimental effects,” Perkins said. These effects could include lower reproduction success, less birds hatching and making it to the fledgling stage, damage to their immune systems, negative effects on feather growth, and other issues.

Since there had been little previous research on how levels of mercury affect shorebird species, Perkins and her colleagues based the study on previous research that focused on Carolina wrens (Thryothorus ludovicianus). This research showed a 10 percent reduction in nest success when there was at least 0.7 micrograms of mercury per gram of blood. “This was the most similar species we have this data for,” Perkins said.

With help from a collaboration with the U.S. Fish and Wildlife Service employees, the team collected blood and feathers from 10 different shorebird species such as the semipalmated sandpiper (Calidris pusilla), the American golden-plover (Pluvialis dominica), the pectoral sandpiper (Calidris melanotos), and others. They then analyzed the blood and feathers to determine the mercury concentration in the birds.

The researchers found that different species had different levels of mercury, but some had high concentrations that had caused reproductive issues in wrens. “We found the most mercury in the semipalmated sandpipers’ blood,” Perkins said, adding that the American golden-plover had the lowest levels of mercury at Barrow.

While the researchers don’t yet know if there’s a direct effect of mercury on these Arctic shorebirds, Perkins says the real concern is that it might be adding additional stress to other threats the birds are facing. “They’re long distance migrants, so they have that stress,” she said. “There’s also habitat destruction and climate change in the Arctic.”

But stopping the spread of mercury to these birds might be difficult, she says. Mercury is a global contaminant that can be deposited on a landscape far from the source which happened in Barrow. Further, the contaminant is persistent, according to Perkins. “The main thing with shorebirds in particular is to reduce other stressors that we have more control over through things like habitat protection,” she said.

Other international efforts are in place to reduce mercury contamination such as the Minamata Convention on Mercury, which is aimed at reducing new mercury impacts to the environment.

Perkins plans to continue looking at shorebirds across the North American Arctic to determine if birds at sites other than Barrow also have high levels of mercury. Data collected on nest success, mortality, and return to breeding grounds for the shorebirds might help determine the effects of mercury on the birds in the future.