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In search of a rare bird
September 18 2006 at 12:27PM
By Mary Esch
Lake Placid, New York - As dusk shrouded the summit of Whiteface
Mountain, Juan Klavins aimed his headlamp at the bird in his left hand,
its head between his fingers and its wing extended to expose a crimson
vein.
The 26-year-old Argentine researcher deftly pierced transparent skin
with a hypodermic needle and filled two fine glass tubes with blood to
be tested for mercury. The bird craned its neck to eye the swarming
gnats, impatient to resume feeding.
The fledgling was a rare Bicknell's Thrush, subject of a long-term
study by the Vermont Institute of Natural Science on the bird's
breeding grounds at high elevations in the Northeast and its wintering
grounds in the Caribbean.
Bicknell's Thrush is a cousin of the American Robin but is smaller and
slimmer, with a brown back and wings, chestnut tail and speckled
throat. Unlike the common Robin, Bicknell's is rarely seen, living in
dense fir forests on high mountaintops. It is identified more often by
its lilting flute-like song than by sight.
Although Bicknell's is not formally listed as endangered or threatened,
it is among the rarest of American songbirds.
"The reason we started studying this bird is that it's not only very
rare, but it also requires a very specific habitat that faces a variety
of threats," said Chris Rimmer, who started the Bicknell's study in
1992 with a colleague at the institute.
The species breeds only in scrubby boreal forests above 840m on top of
mountains in New Hampshire, Maine, New York, Vermont and eastern Canada.
"It's a difficult bird to study because it's distributed across a
fragmented range of mountaintops which we sometimes refer to as 'sky
islands'. We estimate the total population to be between 20 000 and 40
000 birds," Rimmer said.
The bird's habitat faces potential threats from ski area development,
communications tower construction, wind energy projects, acid rain,
mercury and global warming.
"Every one we've sampled has mercury in its system, although we don't
know yet whether the level is high enough to adversely affect them,"
Rimmer said. "This was a very surprising and compelling finding for the
science community."
For the last five years, an annual census by volunteers called Mountain
Birdwatch has documented a seven percent annual decline of Bicknell's,
Rimmer said.
"We really need more time to make any meaningful conclusions, but that
does provide further evidence that we need to be concerned."
It has been well documented that loons and other water birds suffer
neurological and reproductive problems linked to high mercury levels
from eating fish. Now, it appears mercury is moving up the food chain
from soil to insects to birds, even on the highest mountains, Rimmer
said.
Like acid rain, much of the mercury causing pollution in the Northeast
drifts from coal-burning power plants in the Midwest.
Among all the potential threats to Bicknell's habitat, global climate
change is the most worrisome, Rimmer said.
"If current trends continue, over the next 50 years we're going to see
a dramatic change and loss of the balsam fir forests that these birds
require," he said.
There are also serious threats to the bird's winter habitat, the
Caribbean island of Hispaniola, which includes Haiti and the Dominican
Republic, where 90 percent of the total population of Bicknell's Thrush
is believed to winter, Rimmer said.
The Olympic Regional Development Authority in Lake Placid, which
operates a state-owned ski centre on Whiteface, launched a project this
summer in co-operation with environmental groups to raise money to
protect Bicknell's habitat on Hispaniola.
The ski centre scaled back expansion plans and funded a study of
Bicknell's habitat on Whiteface in 2005.
In the Adirondacks, nearly all mountaintops are part of the state-owned
Forest Preserve, where tree-cutting and development are banned. As a
further protection, Governor George Pataki has declared all state-owned
mountains above 840m to be Bird Conservation Areas. About 28 000ha in
the Adirondacks support breeding populations of Bicknell's.
Bicknell's Thrush was considered a subspecies of the more widespread
Gray-Cheeked Thrush until 1995, when a Canadian taxonomist demonstrated
it was a distinct species.
Because Bicknell's has been identified as a species so recently, it
makes an intriguing research subject, said Brendan Collins, 32, a
Vermont school teacher who did graduate work on Bicknell's and spends
vacations working for the Vermont Institute.
"Every year, we learn so much about this species that wasn't known
before," Collins said.
For example, males outnumber females 2-to-1, and both males and females
mate with different partners. Each nest has young from different males.
As a result, each nest usually has several different males feeding the
babies.
Institute researchers have had the rare experience of capturing the
same bird in both its summer and winter territories.
"In 1995, we banded an adult male on Mount Mansfield in Vermont, and
six months later the same bird flew into our mist net on a remote
mountain in the Dominican Republic," Rimmer said. "We caught the same
bird again on Mount Mansfield in the summers of 1996 and 1997."
After they published a paper about that in 2001, the researchers netted
a Bicknell's on another mountain in the Dominican Republic in 2004 that
they had banded the previous summer on Vermont's Stratton Mountain.
"It provides a compelling biological link between Vermont and the
Dominican Republic, and underscores the need for conservation on both
ends of the bird's range," he said.
Collecting the data requires long days in the field. Before their trip
to Whiteface, Collins, Klavins and 22-year-old Pat Johnson of Hanover,
New Hampshire, awoke at 3.45am on a Catskill peak 241km to the south,
finished sampling birds there, carried 36kg packs down the mountain and
drove to the Adirondacks.
In the fading light on Whiteface, they strung 800m of mist nets along a
rocky trail and went to work collecting blood and feather samples,
measuring bills and wings, noting body fat and parasites, clamping
identification bands on legs, and writing down numbers by the light of
headlamps and flashlights.
After a few hours dozing in sleeping bags on the ground, they arose at
4am for the morning netting, followed by an afternoon nap on sun-warmed
rocks.
On the Net: Vermont Institute of Natural Science
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