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Amid huge power transmission towers, tiny songbirds are studied

  • University of New Hampshire graduate student Erica Holm attaches an identification band on the leg of a yellow-throated warbler for a field study on migratory songbirds at the transmission line right-of-way off 1st Crown Point Road in Strafford. JOHN HUFF / Foster’s Daily Democrat

  • UNH student Steph Copeland sets up a mist net to capture birds for banding and cataloging for a field study on migratory songbirds in Strafford. BELOW: UNH student Erica Holm measures, weighs and determines age and sex of a yellow-throated werbler recently. JOHN HULL photos / Foster’s Daily Democrat

  • University of New Hampshire graduate student Erica Holm studies an American goldfinch after attaching an identification band on its leg for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Road in Strafford. [John Huff/Fosters.com]

  • Matt Tarr, Wildlife Biologist at the University of New Hampshire Cooperative Extension talks about the process for safely netting and cataloging migratory songbirds at a field study site in the transmission line right-of-way off 1st Crown Point Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire undergraduate student Steph Copland sets up a mist net to capture birds for banding and cataloging for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire graduate student Erica Holm measures, weighs, determines age and sex of a yellow-throated werbler after banding it for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire research assistants set up a mist nets to capture birds for banding and cataloging for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire graduate student Erica Holm attaches an identification band on the leg of a red-eyed vireo for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire graduate student Erica Holm attaches an identification band on the leg of an American goldfinch for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • A yellow-throated warbler is banded, measured, weighed and its age and sex recorded for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire graduate student Erica Holm measures, weighs, determines age and sex of a yellow-throated warbler after banding it for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • University of New Hampshire graduate student Erica Holm measures, weighs, determines age and sex of a yellow-throated warbler after banding it for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • Research Assistant Casey Coupe demonstrates how a mist net captures birds to be cataloged for a field study on migratory songbirds at the transmission line right-of-way off 1st Crown Point Rd. in Strafford. [John Huff/Fosters.com]

  • A red-eyed vireo has an identification band attached to its leg and is then weighed, measured and cataloged for a field study on migratory songbirds at the transmission line right-of-way off 1st Crownpoint Rd. in Strafford. [John Huff/Fosters.com]

  • Research Assistant Casey Coupe carries a specimen in a brown paper bag to be cataloged for a field study on migratory songbirds at the transmission line right-of-way off 1st Crown Point Road in Strafford. [John Huff/Fosters.com]



Monitor staff
Wednesday, May 31, 2017

Erica Holm turned over the tiny yellow-throated warbler she held in her left hand, legs carefully held between two fingers, and blew on its chest.

“I try to use hot breath for this,” said the Hudson resident, as if apologizing for disturbing the tiny subject of her research on Wednesday’s cold, damp morning.

The bird, weighing barely one-third of an ounce, lay patiently as its feathers ruffled aside, giving Holm a quick look at its body.

“Fat is zero,” she reported, as she jotted the data in the research journal. “Fat layers would be seen as yellow coloration – their skin is clear.”

The quick look also confirmed the bird’s sex, partly because he lacked a brood patch, an area of featherless chest that females of some bird species have, allowing better direct skin contact with eggs in the nest.

Holm is working as part of a UNH project to see whether the scrubland that grows up near major power transmission lines is helping songbirds cope with the loss of habitat to development. That requires data about bird populations and habits, which is why a team of students and researchers will be catching and analyzing hundreds of birds throughout New Hampshire and Maine over the next two years.

Species specifics

Holm’s work with this warbler included measuring lengths of various feathers and the always-tricky task of figuring out a bird’s age. Coloration patterns on the wings and the shape of tail feathers – which tend to be pointed in yearlings and squarer in older birds – led to the categorization of S.Y., meaning “second year.” This warbler was probably born nearby in 2016 and has returned to breed after spending a winter down south.

“It depends on species and specifics, but about half of breeding males make it back to the same place after a round trip from the tropics. They can come back to the same quarter-acre patch,” said Matt Tarr, an associate professor of wildlife and conservation biology at UNH, and Holm’s academic adviser. “They use their previous experience to make decisions about where to nest. There’s no point in wasting resources looking for somewhere new if it was successful last time.”

After placing a tiny bird band on its left leg – the aluminum ring has a unique ID number that will be included in a national database of banded birds – Holm put the bird in a small paper bag and weighed it: 10 grams, roughly one-third of an ounce. After that, she carefully pulled it out and let it go, irritated but unharmed.

Then she turned to the next bird, sitting quietly inside another paper bag and brought to her table by a troupe of UNH undergraduates working with Tarr.

The birds are caught in mist nets, roughly 12 meters by 4 meters in size, that are spread out between two poles. The teams place the nets in the morning, up to a dozen at this site depending on how many workers are available, and monitor them. Birds can’t see the thin, black line that makes up the nets and fly into it, tumbling down into pockets called trammels.

Use of mist nets is the best way to find out more about birds like this, which are too small to carry radio transmitters, as they go about their daily life.

“These critters are difficult to study. You can study them in their nests, and as fledglings, but we haven’t had a chance to focus research on other times of their life,” Tarr said.

Extracting the birds from the nets without harming them takes practice – Tarr had the undergraduates practice with birds at bird feeders.

“When the ground is wet like this, we don’t want them falling on the ground and getting cold,” said Steph Copeland of Delaware, a biomedical science major, as she set up a net for its four-hour session. “When it’s hot, we’ve got to be careful not to get them too hot. We put the banding station in the shade.”

Some species realize quickly that they can’t escape and quiet down, but others aren’t so cooperative.

“A lot of the warblers are so small, they’ll just sit there and wait,” said Tessa Chambers of Alton, a senior studying conservation biology. Catbirds, on the other hand, never stop struggling, often re-entangling themselves in the net just as they’ve been freed.

The birds are put in small paper bags, where the darkness calms them down, and taken to Holm for processing.

Not all attempts are successful. As Holm processed one warbler, a call came over the radio: “I’ve got a bird – oops, it just flew off.” Its species (towhee) and location (net No. 9) were recorded anyway.

Holm knew she’d be doing this a lot: On Tuesday, their first day at this site off Jodi Lane in the eastern corner of Stafford, the group banded 50 songbirds of 16 different species caught in one of the 12 nets they string.

There was no indication that the pace Wednesday would be any slower.

Unusual location

This sort of work is standard for field ornithology, but its location is a little odd: not some remote forest or pristine field but among the massive pylons carrying two of Eversource’s main 345-kilovolt transmission lines in a corridor running through Strafford that connects southern New Hampshire and Maine.

Tarr’s research is studying the role that such corridors provide for New England songbirds, whose numbers have been declining as development slowly reduces the amount of suitable habitat.

“You can’t help but appreciate the habitat value that a right of way may have. It doesn’t look like much, but there’s variety here,” said Tarr, gesturing at the chest-high hardwood trees, bushes and thorny brambles that make the land tough going for anybody who leaves the dirt path running down the middle.

This right of way is large, roughly 200 feet wide, and that is key, Tarr said.

“It’s wide enough to let a lot of sun in, produce a lot of growth. There’s food here – fruit, insects – and cover from predators,” he said.

With about $250,000 in funding from the U.S. Department of Agriculture and the National Fish and Wildlife Foundation, a private nonprofit, Tarr and Holm want to better understand how much of a role rights of way play in providing places for songbirds to breed. They have started a two-year project to analyze various types of power line rights of way – some in Maine where the power company controls plants with herbicides, some in New Hampshire that have been mowed recently and some mowed several years ago, and some that are overrun by invasive plants like buckthorn and Japanese knotweed.

They’re also studying scrubland that has been deliberately created by cutting forests to help an endangered species of rabbit, the New England cottontail.

“We want to see if certain management techniques are better than others,” Tarr said. “Should we be cutting more forests for scrubland, or not?”

Both Tarr and Holm realize that power lines are controversial, and that some eyebrows might be raised because some of the Fish and Wildlife Foundation money comes from Eversource. They say that they’re not trying to support any particular point of view regarding power lines, and whatever data they find will fuel their research.

“We might find that power lines are worse habitat,” Holm said.

Small data

And there’s certainly a lot of data. For each, bird there are 11 data points from weight and length of the tarsus leg bone to the nine-digit ID number that would identify this bird via the U.S. Geological Survey bird-banding database should it be caught again.

The team will also be counting the amount and type of fruit around each net as an indication of available food supplies, as well as take exhaustive surveys of vegetation using what is known as the point-intercept method.

All of this is potentially interesting and important, but not all of it will be used by Tarr and Holm.

“These are not for my study, but they could be related to work done by other people,” Holm said. “They are going into a bird database so that other people can use it and can make conclusions without having to go out into the field.”

One main measurement that Holm will use in her work – because science requires quantification – is “bird captures per net hour,” a broad indication of species population in each area.

Tarr said he hypothesizes that many bird species thought to live in forests also depend on scrublands for at least part of their life cycle – particularly after fledglings have left the nest and birds are feeding voraciously, filling up before their long wintertime migration to the tropics.

“We suspect these areas are important for all species at some time in their life,” Tarr said.

Scott Hall, a scientist with the National Fish and Wildlife Foundation, said that work could fit into a bigger research picture, which is changing the former view that forest bird species and scrubland bird species are separate.

“It’s more of a continuum,” he said.

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)