A long term environmental study of a "rare" bird species

To: Birding Aus <>
Subject: A long term environmental study of a "rare" bird species
From: L&L Knight <>
Date: Wed, 20 Sep 2006 20:59:57 +1000 index.php?set_id=1&click_id=143&art_id=qw1158556142909S553

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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