July 24, 2005
Mercury pollution threatens mountain songbirds
By DAN SHAPLEY
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
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
"In my mind you have this double-whammy effect," Evers
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."