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Thrush Hour 

Watching the birdies takes Kent McFarland to great lengths — and heights

What do you call a guy who spends 18 hours a day braving biting insects, enduring extreme weather and clambering down hidden precipices while bushwhacking through some of the densest off-trail brush on Mount Mansfield — all in an effort to follow the movements of a certain small, brown song bird? “Air idiot,” says his co-worker. “A freak,” suggested his predecessor. But Kent McFarland, an environmental biologist and researcher with the Vermont Institute of Natural Science, prefers the more flattering designation, “Bicknologist.” His investigation of the elusive Bicknell’s thrush involves just this type of extreme birding.

Working with research director Christopher Rimmer, about a dozen field workers and more volunteers, McFarland has spent six years tagging, blood-testing, radio-tracking and videotaping the bird. He’s emerged as one of the world’s leading experts on Bicknell’s thrush — a rare avian variety that wasn’t even considered a distinct species until 1995 and today is ranked as a top priority for protection. Along the way, McFarland also has played with a whole bunch of high-geek technology, become ultra-sensitive to inaccurate bird songs in movie soundtracks and, he claims, developed a natural immunity to black flies.

There are only about 25,000 Bicknell’s thrushes in existence, and those numbers are apparently diminishing. The bird spends its winters in the broad-leafed forests of the Dominican Republic. It summers at 3000 feet on the isolated mountain peak “islands” in New York, New England and Eastern Canada. In Vermont, concentrated communities can be found on Mt. Mansfield and Stratton Mountain — and so can McFarland.

On Mansfield, he works out of a barracks-like, cinder-block structure nestled in the side of the mountain near the top of the Octagon ski lift, a place McFarland and his co-workers call “the highest basement in the world.” During snow season, the ski patrol uses the building. This time of year, it has a decidedly student-housing feel, with clippings about snoring taped up over cots, bird books and binoculars laid out on the shelves and more than a few empty beer bottles among the bean cans and peanut butter jars in the kitchen.

McFarland majored in environmental studies at Allegheny College. After getting hooked on birds during a three-year stint with the Peace Corps in the tropics of Paraguay, he earned his master's at Antioch New England. At 33, he still looks very much the student, with ovoid wire-frames, a VINS baseball cap pulled over his short, strawberry blond hair, baggy cargo pants, sneakers and a plaid flannel shirt with the buttons cut off. This last detail isn’t his attempt at a fashion statement, he’s quick to explain. It’s his solution to the problem of getting tangled up in the mist netting — fine, black nylon mesh that’s invisible and harmless to the birds it snares when it’s stretched out in the wild. Piled up between uses, the netting looks like a cheap wig.

When he’s out in the field, McFarland may top off his costume with a multi-pocketed vest. In one pocket, he might store a radio signal receiver the size of a fat paperback and connected to a six-prong, hand-held antenna. Over his vest, he may carry his brand new, bright yellow, $10,000 Trembler global-positioning device that resembles something from a low-budget sci-fi thriller and communicates with a satellite to pinpoint within a meter the location of, say, a nest.

“I enjoy the technology aspect as much as the wildlife,” McFarland confesses. But what’s particularly exciting about the technology, he adds, is how much it has helped his team learn about Bicknell’s, and how quickly. “People always glorify field biology. They think it’s like the Discovery Channel,” comments McFarland, whose work was featured several years ago on Discovery’s “All Bird TV” show. But just as every minute of fascinating nature film requires hundreds of hours of tedious footage, each morsel of useful data added to the VINS study represents hundreds of hours of labor.

As Jeff Farrington, a graduate student who works with McFarland, puts it, “With this sort of project, you’ve gotta make hay while the haying’s good. They’re haying now.”

On the mountain, the workday for both the birds and the birders begins in the pre-dawn darkness, just before 4 a.m. The scientists set their nets, and any Bicknell’s they manage to trap is fitted with a uniquely color-coded metal band around its leg and a tiny radio transmitter on its back. The transmitters are attached to the birds with fishing line looped around the tops of the wings, backpack-style. Once the birds have preened themselves, the gray plastic lumps of the receivers get hidden under the feathers, and all that shows is the projecting end of the six-inch wire antenna.

Before a thrush is released, the researcher will also take a few drops of its blood for DNA testing.

Until as late as 10 p.m., field workers will track and record the thrushes’ movements manually, following the signals sent out by their radio receivers, and on videotape, with cameras trained on the birds’ nests. Either approach tests the investigator’s endurance, literally plunging the scientist into the seemingly impenetrable underbrush that the Bicknell’s thrush calls home. “If you see a patch that’s so thick you say, ‘I don’t want to go in there,’ that’s where it will be,” McFarland advises.

One such patch is located within a stone’s throw of the commercial transmitter tower at the foot of the mountain’s nose. The rain has finally stopped, and a swirl of clouds is lifting off the chin. We stride past the sign that identifies the area as “restricted for scientific study only” and step off the marked path. The sharp needles of young balsams scrape our skin and dead branches ricochet towards our eyes as we fight our way through the growth, pausing every few steps to check the dancing meter on Farrington’s portable radio receiver reporting cold, warmer, hot, warm as the distance between us and the thrush contracts and expands. Underfoot, the ground is carpeted with brilliant green moss, and it feels soft and irregular from the decaying dead wood beneath. It’s like swimming through trees and stepping on pillows.

From somewhere above us, McFarland hears a thin zi-zi-zi-zi-zi-zi-zi-zi-zi. “Blackpoll overhead,” he announces, binoculars to his eyes. Then, “Male Bicknell with a bunch of food.”

“Female with a feather,” Farrington replies, also looking. “She’s still building?”

“Psh, psh, psh, psh, psh,” McFarland whistles softly between his teeth, hoping to conjure the male Bicknell back into his sights long enough to let him check the bird’s ID bracelet. A light rain begins to fall. Flies drift around our faces. McFarland whistles again and his call is answered. “Purple dark blue light blue x on the right,” he tells Farrington, who writes it all down in his waterproof notebook.

Before leaving the thicket, we take a look at the nest itself, a tight fist about five feet off the ground, snuggled in the crook between a branch of a balsam and its trunk. The outside of the nest is trimmed with moss. McFarland says the inside is lined with a horsehair fungus that may have antibiotic properties, but all you can see, peering in, is a clutch of four little eraser-pink heads with closed eyes and downy black fuzz: day-old thrushes aiming their oversized beaks towards the sky.

When these chicks have reached five days old, McFarland’s group will grab them from their nest just long enough to band them, weigh them and to draw a drop of their blood that will be DNA tested.

Like only about 20 known bird species, Bicknell’s thrush follows a libertine love practice naturalists call “cooperative polygynandry,” in which both females and males take multiple partners. Females lay four eggs at a time, each of which may have been fertilized by a different father. Males mate with several females and help tend all the nestlings they may have sired.

Radio tracking doesn’t always go this smoothly. One time, McFarland and his crew found an abandoned nest full of dying fledglings. They followed the mother’s radio signal all the way to Underhill, where they found her transmitter, sans thrush, among the stinking carnage in the nest of a sharp-shinned hawk.

Another Bicknell’s was once found, dead but still fully intact, in a weasel’s hole. McFarland also tells the story of the time a nest was too high for him to see into, so he blindly reached in with his hand to check the contents. Rather than feeling smooth eggs or hot, fuzzy heads, “I felt goo,” he remembers, grimacing. The chicks had died, he explains, “and when I pulled our my hand it had maggots all over it.”

While hawks and weasels prey on adult Bicknell’s thrushes, red squirrels make short work of their eggs. In one VINS video, a red squirrel can be heard off-camera for quite a while before the predator finally flushes the mother bird from her eggs and sits down on its haunches in the middle of the nest. Then the squirrel takes one of the freckled blue eggs between its front paws, twists the egg around until its thin part is at the top, bites off the top of shell, and licks out the contents. Once the shell is empty, the squirrel tosses it aside and starts on the next one. When all the eggs have been consumed, the squirrel urinates into the nest.

To avoid giving squirrels and other predators any extra advantage, McFarland and his coworkers try to reach the nests they study by a variety of different routes. But the scientists acknowledge that the biggest threats to Bicknell’s thrush are in the air and land themselves, both here and in the Caribbean. McFarland, who wrote his master's thesis about the impact of road construction on bird species in Belize, is studying the effects of ski-trail development on the thrush.

Air pollution is also a major concern. “The acid precipitation is wicked bad,” McFarland observes. A recent UVM study showed that the clouds that so frequently cloak Mt. Mansfield are “like lemon juice.” Trees bathed in these clouds will eventually die, and thrush nesting sites will disappear. Airborne mercury gets into the birds’ system, threatening their health. Though tests are still incomplete, McFarland believes they will turn up “significant” mercury content in the blood of the birds.

At the end of the season, McFarland and the thrushes will both move off the mountain. While the birder returns to his hometown of Woodstock, the birds will migrate to the Dominican Republic — where they’re likely to find fewer rooms at the inn than last winter. With more and more of the forest being replaced by banana and cocoa palm plantations or “just ratty old fields used for cattle,” McFarland says, all but 3 percent of the birds’ original habitat is gone. “Conservation down there is less than wonderful,” he opines. “There are too many humans on that island.”

That may well be. But why does the world even need Bicknell’s thrush? “Why does the world need humans?” McFarland replies. “I guess they have just as much right to be here as we do.”

For all his avian advocacy, however, the researcher wonders how he got hooked on a species that plays so hard-to-get. “Why didn’t I take up mallards?” he muses as he lumbers down the side of the mountain chasing after the next dim radio signal. ‘Then I could just set up a lawn chair in the middle of the Woodstock town green, set out a six-pack and spend the whole day just marking down the birds’ color bands.”

The answer is undoubtedly in the numbers. If mountaineers scale peaks “because they’re there,” bicknologists like McFarland study their thrush because they may not be there much longer.

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