New York Times  [Printer-friendly version]
August 8, 2005


[Rachel's introduction: Precautionary action can take many forms. An
early warning system is an important kind of precautionary action,
monitoring local conditions to keep good things going or stop bad
things from happening. This story describes an early warning system
that's testing for mercury in wildlife in the Catskill Mountains of
New York.]

By Anthony Depalma

Hunter Mountain Wild Forest, N.Y., Aug. 3 -- So far this summer, Wing
Goodale and his boss, David C. Evers, have used decoys and recorded
bird calls to lure about 150 thrushes, warblers and other wild
songbirds into nets here and in several others parts of New York
City's Catskill Mountain Watershed to determine what is happening to
the drinking water.

From each tiny bird, no bigger than a cellphone, Mr. Goodale, a
research biologist, gently takes blood samples with toothpick-size
pipettes. Then Mr. Evers, also a biologist, stretches out a bird's
wing and counts down to its 11th flight feather, which he deftly
plucks and puts into a plastic storage bag for sampling.

Mr. Evers, who is executive director of the BioDiversity Research
Institute, a nonprofit research and education group in Gorham, Me.,
is looking for signs of mercury in the songbirds. He has a pretty
good hunch that he will find it, as he has already found mercury in
songbirds in the Adirondacks and in New England.

If substantial amounts of mercury show up in the blood and feathers
he has collected, it could spell trouble for the watershed and,
potentially, for the nine million people who rely on the New York
drinking water that comes from here because it would mean that the
toxin is present in ways that were previously unknown.

"It's far more extensive than was ever put forth to the public," Mr.
Evers said.

Mercury contamination has long been present in lakes, rivers and the
city's reservoirs.

Mercury, a liquid metal, does not get into water because of broken
thermometers, as some believe. Rather, mercury occurs naturally in
the earth, including in coal. It is released into the air by coal-
burning power plants and other sources.

Emissions from power plants in the Midwest drift toward New York. The
real problem comes when the airborne mercury comes into contact with
water and is transformed into its toxic form, methylmercury. Although
the water in New York City's Catskill reservoirs is considered safe
to drink, state health officials have posted advisories warning that
pregnant women and children ought to limit their consumption of bass,
trout and other fish caught in the reservoirs because the fish have
absorbed some of the toxic material.

Until recently, the mercury problem was thought to be limited to
water. The discovery of mercury in songbirds that never go into the
water may represent a serious new threat.

Mr. Evers was invited to the watershed by the New York chapter of the
Nature Conservancy, a national environmental group that has helped
protect open spaces throughout the state.

In recent years, New York City has spent about $175 million to buy
about 60,000 acres of Catskill woodlands to protect the reservoirs.
But what good is buying forest land, asked Alan White, director of
the conservancy's Catskill Mountain Program, if the health of the
forest itself is at risk?

It is still early in the investigation, but Mr. Evers, who spent more
than a decade studying the impact of mercury on water birds like
loons, believes that the harmful form of mercury gets caught in the
fallen leaves and other litter on the forest floor, where it is
consumed by sow bugs, centipedes and other small insects.

As those bugs are eaten by larger bugs, the mercury content is passed
on. The buildup of mercury continues as those insects are eaten by

Mr. Evers and Mr. White say that it makes sense to think of forest
songbirds as early warning systems, like the canaries that used to be
carried into coal mine shafts. If the canaries died, miners hurried
out of the mines because they knew that dangerous methane or carbon
monoxide was present.

In the same way, unnatural levels of mercury in songbirds could be
interpreted as a sign of pending danger in the forests. In loons and
other water birds, excessive levels of mercury cause erratic behavior
and lower birthrates.

The scientists in the Catskills are focusing their attention on the
wood thrush, a gutsy little frequent flier with a flutelike voice
that can combine two notes at once. The wood thrush can migrate as
far south as Panama, more than 2,500 miles from the Catskills.

In recent decades, the number of wood thrushes has declined 45
percent, and the reason is unclear. Mr. Evers says biologists
initially suspected that destruction of the bird's winter habitat was
responsible. But now he thinks elevated levels of mercury could be to

The connection between mercury in the birds and the purity of the
city's drinking water is indirect, but real. As Mr. White explained,
if the songbird population declines, the natural check on insects
will be disturbed.

Without the birds preying on them, caterpillars and other destructive
insects can defoliate forests, killing trees that filter runoff that
eventually winds up in the reservoirs.

Before dawn, Mr. Evers and Mr. Goodale set up nearly invisible traps,
called mist nets, along a trail on the western slope of Hunter
Mountain, in between the city's Schoharie and Ashokan Reservoirs.

On the forest floor near the nets they placed plastic decoys and CD
players that reproduced the thrush's beautiful ee-oh-lay song.

By 8 a.m. they had trapped about 10 birds, including several wood
thrushes. Because the wood thrush is somewhat larger than other
forest songbirds, it is believed that it will show a higher level of
mercury when the tests are completed in about six weeks.

If these initial studies of songbirds indicate, as expected, that
there is a serious problem with mercury, Mr. White said the long-
range concern would be that "these forest systems will start to
unravel," endangering the water supply.

Mr. White said that there was no immediate health danger, and the New
York City Department of Environmental Protection, which runs the
city's water system and continuously tests for mercury, has not
detected the element in the water.

New York is one of only a handful of cities in the country that do
not filter their drinking water. What goes into the upstate
reservoirs comes out in New York taps 120 miles later unfiltered,
although chlorine and fluoride are added.

Mr. Evers says it is much too early to determine what the impact of
mercury on the songbirds might be, or how long before the reservoirs
are affected in any way.

But he said that, when it comes to drinking water, it is important to
anticipate a potential problem.

"The wood thrush is a good indicator species," Mr. Evers said. "If
this small-scale, pilot project shows that there is a danger in these
parts, it will be time to go to the policy makers and say this is
what we've found, and we should do something about it."

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