Fishkill Ridge
Community Heritage

Mercury Effects More Than Fish, and Birds That Eat Them


Piliated Woodpecker Sunday, July 24, 2005

Mercury pollution threatens mountain songbirds

Scientists are at work verifying a startling prediction for mountain songbirds in the Shawangunks, Catskills and Hudson Highlands ­ mercury air pollution could be accumulating in their flesh at damaging levels.

A landmark series of studies published in April found a toxic form of mercury can accumulate in songbirds that eat insects, not just fish and the birds and animals (including people) that consume fish, as previously thought. The studies also predicted the Catskills and nearby mountains are at particular risk because of smokestack emissions from Ohio, Pennsylvania and West Virginia.

Now, David Evers, the executive director of the Biodiversity Research Institute in Gorham, Maine, is following up on those studies at sites across New York with the help of the Nature Conservancy. Evers edited the April studies that appeared in the journal Ecotoxicology.

Wednesday, Evers and helpers set up mist nets to catch birds such as hermit thrushes at the Sam's Point Preserve on the Shawangunk Ridge in Cragsmoor, a public park owned by the Open Space Institute and managed by the Nature Conservancy. They deployed decoys and recordings of bird calls to draw birds toward the nets, which resembled fine-meshed badminton nets with pockets that catch birds that intersect them in flight.

Evers and Tim Tear, director of conservation science for the Nature Conservancy's Eastern New York Chapter, plucked a couple feathers and took a few drops of blood from each bird they netted, and then released the birds unharmed.

Assessing the damage

The blood and feathers will be analyzed for mercury and calcium levels this fall. It will be the first look at how mercury is accumulating in birds in local mountains, and could verify the prediction that they are badly contaminated.

Calcium is tested because it indicates several things about the health of birds and their environment.

Calcium is scarce in acidic environments so birds have to forage more to get enough of it to form eggs and bones. Acid rain and mercury come hand in hand because the bacteria that converts mercury to its toxic form thrives in acidic environments.

Because mercury is toxic to the brain, it can make birds lethargic. High mercury levels could slow foraging adults down, preventing them from getting enough calcium and limiting their ability to rear young.

"In my mind you have this double-whammy effect," Evers said.

Because insect-eating birds get their calcium from millipedes, pill bugs and other shelled bugs, scientists will test bugs and spiders for mercury too.

Some of the birds likely to be exposed to mercury are in decline, but the role mercury plays in those declines is unknown.

The Nature Conservancy is hungry for the results because its strategy to protect sensitive species is now focused on protecting land from development. The air may be as important as the land to the survival of some species.

"We didn't know the direct impact of air pollution to lands and waters we're concerned about protecting," Tier said. "There's so much information coming out over the last decade or so, that it's made it something we need to pay attention to."

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