Bethany Gregory, a field technician with GAI Consultants, walks into the woods with a headlamp to check mist nets for bats to make sure the planned Silver Line train yard near Dulles Airport doesn’t affect bats living in the nearby woods. (Evelyn Hockstein/For The Washington Post)

The work isn’t glamorous and the hours aren’t great, but when Cynthia Hauser gazes into the eyes of a bat, the ticks, the mosquitoes and the ever-present danger of Lyme disease seem to just fade away.

Hauser loves bats. She always has — starting from her days as a teenage spelunker in Pennsylvania.

And it’s that passion that has brought her and three colleagues to this muddy, overgrown field north of Dulles International Airport on a steamy, sticky July night. These acres of trees, tall grasses and wild blackberry bushes may soon be leveled to make way for a new rail yard to accommodate hundreds of Metro rail cars as part of the multibillion-dollar Silver Line.

That is, unless Hauser and her team find that among the many species of bats snoozing in the trees is one particular type: the northern long-eared bat, recently declared “threatened” under the Endangered Species Act.

Such surveys are required when a project involving a federal agency might encroach on the habitat of a threatened or endangered species, according to Catherine Hibbard, a spokeswoman for U.S. Fish and Wildlife Service. The presence of just one of these bats won’t stop the project, but it could mean a potentially costly delay of several months.

Bethany Gregory hangs a mist net for a bat census to make sure the planned Silver Line train yard near Dulles Airport doesn’t affect bats living in the woods near the site. (Evelyn Hockstein/For The Washington Post)

It was in May when officials with the Metropolitan Washington Airports Authority, which is overseeing construction of the $5.8 billion rail line, became aware that these tiny bats with their distinctive ears might be an issue. They hired GAI Consultants to survey the parcel, which is more than 90 acres. Spokeswoman Marcia McAllister said that the MWAA will pay about $40,000 for the survey and that the cost will probably be covered by the project’s $551.5 million contingency fund.

Like many of their relatives, northern long-eared bats, so named for their distinctive ears, have been victims of white-nose syndrome, a fungal disease that is killing bats at alarming rates.

‘Not the greatest habitat’

It’s nearly dusk when the survey group arrives in the field just off Old Ox Road. They don bright orange construction vests, hard hats and goggles before spraying themselves liberally with tick and mosquito repellent. Part of the field has recently been mowed, but lurking in the remaining grassy areas are a bevy of creepy-crawlies, many of them out for blood.

As a precaution, team members seal the space between the bottom of their pants and the tops of their boots with duct tape. In this line of work, bats are perhaps the least scary of the creatures they’ll encounter.

It’s a far more urban setting than most of the places they work, Hauser says. For example, every few minutes, the symphony of crickets and frogs is punctuated by the roar of a jet on approach to Dulles Airport.

“It’s not the greatest habitat for the long-eared bats,” Hauser says, eyeing a plane as it cuts through the evening sky headed west toward the runway. It’s not just the noise. Bats tend to prefer older trees with peeling bark, and most of the trees in this wooded area are younger and greener. Hauser points to the lone exception, a tall, dry, hollowed out specimen sticking up through the rest of the canopy. As far as bat roosts go, it’s an excellent spot.

Bethany Gregory holds a red bat after it was caught in a mist net during a bat census to make sure the planned Silver Line train yard near Dulles Airport doesn’t affect bats living in the woods near the site. (Evelyn Hockstein/For The Washington Post)

The team will be here for seven nights. They’ll set up six mist nets, which they’ll move every third night, lest the bats and other winged creatures catch on. The best spots, Hauser says, are forested corridors near water — sort of like tunnels within the forest — because the bats have room to fly, but the space is still somewhat confined, making it easier to catch them in the nets.

“They use corridors like we use roads,” she says. And just as humans sometimes shift to autopilot as they drive along a familiar roadway, bats will do the same when flying along familiar routes.

Strung between two poles, the assemblages resemble giant volleyball nets. The bats fly in and fall into small pockets where they’ll be retrieved by a member of the team.

One net is a few hundred feet from the white pickup truck that serves as the team’s makeshift office. In the back, they’ve laid out the equipment they’ll need for tonight’s shift: a small scale — about the size of an iPhone — that will be used to weigh the bats, a clear plastic ruler that will be used to take measurements and a bottle of correction fluid to mark the bats so they’ll know which ones have already been captured.

Hauser pulls out a small piece of cardboard and carefully unwraps the pink bubble wrap to reveal two tiny radio transmitters. If they catch a northern long-eared bat, they’ll use surgical glue to attach one of the transmitters just under the bat’s shoulder. The hope is that by following the radio signal, they’ll be able to find the bat’s roost.

Just after 8 p.m., Hauser and colleague Bethany Gregory deploy three nets. Deeper in the woods, Amy Schneider and Lisa Sinclair have readied their nets for possible winged visitors. They’ll do checks every 15 minutes, firing off a text if they get a hit.

They settle in and wait, serenaded by a symphony of frogs and swatting at a growing army of tiny blood-sucking bugs.

There’s no telling what will happen. Their first night out, they got eight, but the night before they netted only three.

“Sometimes you get one, sometimes you get 30,” says Gregory, who is in her second year working with bats. This is the team’s third night of observation. “A lot of this job is just sitting. You get a lot of reading done.”

At about a quarter to 9, Hauser and Gregory suddenly straighten in their folding chairs. It’s still light out, but a lone bat is flying tantalizingly close to the top edge of a net. It moves closer and closer, then darts off in the opposite direction. The two sigh in disappointment.

At about 10:45 p.m., Gregory disappears up the hill and into a narrow, wooded clearing where two other nets are set. A few minutes later, Hauser’s phone tweets. They’ve got one.

Hauser flips on her head lamp and makes her way into the clearing. At the first net, she finds Gregory holding a bat no bigger than the palm of her hand. She watches as her colleague tries to pick through the netting.

“I know, I know,” Gregory whispers to the bat. “Almost, almost — you’re almost free.”

She turns to a small group of visitors.

“The hardest part is figuring out how to untangle these guys,” she says. “These guys don’t usually get too tangled.”

Finally, she frees it from the netting. Gregory holds the tiny bat, carefully in her right hand. With a practiced ease, she opens her vest, slips her left hand into an inside pocket and pulls out a small brown paper sack. She carefully places the bat inside and secures the bag with a tiny clip. She shakes the bag gingerly to ensure its wings aren’t caught, before tucking the bagged bat back into her pocket. She smiles.

Back at the truck, Gregory places the bat on the tiny scale.

“It’s a boy,” she says, a young red bat, weighing in at 8.6 grams.

“I call them Ewoks,” Gregory says with a grin, as she displays the bat’s surprisingly furry brown head. They measure his wingspan and examine his teeth. Then, as a final step, they mark the bat with a swipe of correction fluid.

At about 2 a.m. it’s time to pack it in for the night. With only one bat caught, it’s been a long night. But there will be more opportunities.

By the end of the week, the team will have caught and released 61 bats, two squirrels and a small number of disturbingly large moths. And much to the delight of project officials, of the 61, none were the threatened northern long-eared bat.

Those results will be sent to officials at U.S. Fish and Wildlife for review. Hibbard said officials there will examine the results, and if the project is not likely to adversely affect the bats, it will be cleared to move forward.