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Early birds: A project two decades in the making is unlocking secrets from a bellwether songbird

At 5:30 a.m., the forest is dark and quiet.

Off in the distance, you can hear the rushing of a stream. Looking up, the leaves are barely visible against the slowly brightening sky. Stand still and you can begin to hear the murmur of the birds.

Their chatter starts slow, but soon the sky has turned a medium gray and their noises have cascaded up the mountain, surrounding you in a wave of song.

That means it’s time to go see what’s out there.

This is the start of a typical morning for researchers stationed each spring at the Coweeta Hydrologic Laboratory in Otto, North Carolina. For the past 20 years, teams led by graduate students and fortified by undergraduates or recent graduates head out before dawn to tag and track the black-throated blue warbler.

At its core, the project is investigating why this trailing-edge population is declining—the birds migrate from the Caribbean to the East Coast of North America, but this is the farthest south they like to stop before building nests and finding a mate. But what started out as a straightforward task to monitor the “blues” at varying elevations has turned into a multi-decade, groundbreaking project that encompasses climate change, a sister site in New Hampshire with even more data and the potential for insights into species far beyond just one bird.

But right now, the project stands at a crossroads.

“It’s difficult to keep a long-term project going, from a funding standpoint,” says professor Robert Cooper, who launched the project two decades ago when he realized that studying a species at various elevations could connect patterns with climate change. “You pretty much get your funding anywhere you can. Through the years we’ve had funding from two different (National Science Foundation) sources … but in that timespan there were some lean years when we had to cobble together whatever funding we had.”


Small bird, big idea

In the late 1990s, Cooper was looking at data provided by the annual Breeding Bird Survey, a national survey conducted by volunteers for the past 50 years. With this information, it’s possible to look at maps and see large-scale trends over time.

As Cooper read the maps, he could see larger declines of birds in outer regions—the “trailing edge” of migratory birds that, for whatever reason, settle in climates that just barely fit their ideal profile. For black-throated blue warblers, the ideal place to make a nest and reproduce is somewhere cold, but not freezing. This includes New England, New York, even into Canada.

The mountains of North Carolina? Barely. But it’s possible.

“It occurred to me that setting up a study that might look at species on an elevational gradient might be a good avenue to follow to look at climate change,” says Cooper. “Because what you might see on this elevational gradient at low, middle and high elevations might mimic what is going on in the broader range of these species.”

Right around the same time, Cooper met a graduate student named Kirk Stodola who had experience collecting data with a similar premise. Stodola was finishing up has master’s at Mississippi State University, which had no funding to continue the project, so Cooper recruited him for a Ph.D. and enhanced the project, focusing on the black-throated blue warblers. They set up the study to mimic one already in place at Hubbard Brook Experimental Forest in New Hampshire.

“So, we have these two studies that are similar in design and very similar in methodology so we can directly compare these results,” adds Cooper.

Stodola, now a researcher with the University of Illinois Natural History Survey, says his initial research aimed to study a bird that nested low to the ground. He didn’t realize how abundant the blues would be, but it soon became clear that they made excellent study subjects: Male and female calls are identifiable and their nests, while small enough to fit in the palm of your hand, are often built low in mountain laurel and rhododendron bushes. Sometimes, you can even find them nesting just off a mountain access road.

As a new doctoral student for Cooper, Stodola began focusing on and expanding higher elevation study sites where blues were abundant. He had been working at four sites in and around Coweeta, but over time a few were dropped either due to access or because the birds simply stopped nesting there. “We even had a lower elevation site that we used from 2002-2004, and that was another 500 feet below what Bob knows as the lowest site. But the birds just weren’t there,” adds Stodola. “You’d have to travel long distances to get a decent sample size. … So, we have the two sites that are closer to Coweeta proper.”

All the work takes place in the Nantahala National Forest, which encompasses thousands of acres of forested mountains off U.S. 441 in North Carolina, just across the Georgia state line.

Today, small teams of researchers head out to two study sites—a middle elevation site at about 3,800 feet above sea level, and a high elevation site located around 4,500 feet. They begin their work in April, when  the birds first begin to arrive, and stay through July.

When the mountain laurel begins to bloom, they know their time is limited.


Breakfasts of champions

There are dorms on the Coweeta site, but due to budget constraints—and, more recently, closures due to COVID-19—the research teams now call two nearby rental homes their base. They begin hours before dawn, making their way to the kitchen to start the coffee and slather chunks of bread with peanut butter before heading out into the darkness.

This summer there are three teams, one focused on the black-throated blue warblers and the others led by associate professor Richard Chandler and professor Jeff Hepinstall-Cymerman to study several species of songbirds that migrate to the mountain.

The teams forge paths through the forest until early afternoon. They rotate sites and duties—some days could involve setting out delicate nets to snag birds as they emerge from their nests, while other days involve doubling back to check on nests for fledglings. Teams work to tag every bird they see with a unique color pattern, as well as a metal tag imprinted with a specific ID number. Any of these can be used to identify a bird down the road, although the colored bands are particularly helpful, because it allows a bird to be identified by sight alone—just knowing the placement of the colors can match a particular bird to where and when it was first spotted.

It’s research that requires dedication and hard work. And lots of snacks.

“It’s your life. There’s no separation,” says Stodola, who managed teams at Coweeta from 2002 until he received his Ph.D. in 2011. “But we’re fortunate to hire people who like to do that. If it was their off day, they’d probably just go for a hike.”

Is it strange to live with your coworkers? Perhaps, says Stodola. But finding work/life balance in a place where your work constantly bleeds into what you do in your spare time requires a different way of framing it.

“We stress to just enjoy it. It’s one thing to find nests, but if you want to go explore, go explore. Learn your plants, learn the mushrooms. Learn all the other stuff that’s out there while you’re out there,” he adds. “Most of the day you’re out by yourself, so when you come back together, you’re probably tired, but then you’ll have time to share some of the stuff you saw during the day.”

Often, crews make meals together or rotate dinner responsibilities. Evenings include board games or movies. Rainy days are for data entry.

Living and working together as a field crew isn’t all that uncommon, though, says Mason Cline, who took over management of the project with his wife Joanna Hatt in 2011, when Stodola graduated. And even if you don’t get along with your crew, it can still be a good learning experience. Interpersonal skills are essential, whether you’re looking for bird nests or managing a project for a public agency.

“One of the things Joanna and I learned from leading crews is that there are small things you can do that go a long way for camaraderie,” says Cline, who is today is the bird program manager and the migratory gamebird biologist for the New Mexico Department of Game and Fish. “We would make a point to have dinner together with the crew. We would take turns cooking, and it was kind of neat—some of these people had never cooked for anyone other than themselves. It was a good time—you have a meal and work through things over a table.”


Never stop learning

But beyond the camaraderie, the skills students and recent graduates are learning while working on the project are essential to fieldwork in the future. Collecting information and making observations in the field are key skills, says Hatt, who now works as a native fish biologist for the New Mexico Department of Game and Fish. “There will be times you’re successful at a task or you fail, but you have to keep going. It’s a pretty intense experience,” she adds. “I certainly felt this way for myself—it was pretty formative. I learned a lot about myself and I learned a lot about how to do science, and I’m really grateful for that now.”

And the bond continues years after traipsing the North Carolina forests, says Stodola.

“I’ll meet some of my former technicians at conferences; they worked back for me in 2007 or 2008 and they’ll have completed their master’s, and it is kind of fun to see that and know that we essentially had some role in helping them get to where they’re at,” says Stodola. “We gave them their first field job. There are other field positions like that, but not a ton that are long-term and you have housing and everyone’s together.”

But the nests, the tags, the data sheets and the labyrinth of spreadsheets holding two decades of information are also part of a larger learning process that continues to take shape. Sure, some trends were evident just five years after the project started: the blues weren’t flocking to lower elevations like they used to.

As time has elapsed, though, a wider angle reveals even more.

“For example, if you look at the trends in abundance for the middle elevation plot, for the first 10 to 15 years, you didn’t see a strong decline. Instead, you saw a lot of variability between years,” says Chandler, who will oversee the project after Cooper’s retirement. “But now we have another 10 years of data, and you can see there’s a long-term trend. It’s been variable, but over time some of those patterns become evident that wouldn’t have been evident over a shorter period of time.”

Now, Chandler is looking to build off this base of knowledge to get a more detailed picture of the mechanisms causing the population declines. It’s clear that the birds are no longer nesting in lower elevations, and they are now disappearing from the middle elevations. But how is climate change affecting the population?

“There’s a lot of changes going on down here, and it’s probably combinations of things going on,” says Will Lewis, a recent Ph.D. graduate whose thesis involved analyzing the 20 years of data collected at Coweeta and comparing it to the New Hampshire data set. Lewis presented his dissertation earlier this summer. “The key here, I think, is there’s no one smoking gun. Climate can have so many impacts on habitat, physiological stress, changes in predators, changes in disease vectors—maybe it’s not surprising that there are a lot of interacting effects.”

One marker that Lewis is examining is food sources: caterpillars.

Food sources are critical for the blues—when you weigh just a few ounces, one caterpillar can be the difference between life and death. But research has pointed to fewer caterpillars in lower elevations. One strategy could be managing for a diversity of tree species that are favored by the caterpillars, which, in turn, could increase their numbers and bring more food sources. But Lewis says more study is needed to determine how managing trees could affect the blues.

“Population dynamics, and what causes populations to change, is such a fascinating aspect of research,” adds Chandler. “New questions tend to build as you answer old questions, and that is part of the beauty of long-term research. So, I hope this research will continue on as long as we can continue to find funding for it.”

Funding for the NSF portion of the project continues through next year. Cooper says in retirement, he plans to focus on a new long-term grant proposal and, ideally, move the project away from the heartburn of three-year grant cycles.

There have been lean years in the past; Stodola recalls managing a field crew of eight spread across two rental houses, and then other years when he had a crew of three or four (or, just himself for a month to keep things going). Cooper says he hopes that with Chandler taking over the reins, the core of the project can continue while expanding to include additional species and other questions.

“It’s a little bit of a gut punch to think about that project closing down. The long-term data sets provide an opportunity to track what’s happening in a system over time—in this case bird populations, their habitats, food and predators. With a gap in that information, your ability to understand the system is going to be diminished,” says Hatt. “I think the other aspect of that project that would be lost is what that project has done for students—early career professionals—in culturing their appreciation for science and research. Not having that opportunity would be a loss.”

Then there’s the location itself, a natural wonderland of salamanders and songbirds that’s unlike anywhere else in the United States.

Now in the Southwest, Hatt and Cline still recall the lushness of the mountains around Coweeta.

“Maybe this is time passing and me forgetting a little bit, but I think every day you would see something memorable,” says Hatt. “It could be a bear, sometimes your heart would start racing because you almost stepped on a rattlesnake, or you see these little birds that came from thousands of miles away picking up nest material and building a nest. And you could watch it happen.”

Cline agreed. “Everyone’s seen a bird build a nest but being there, out by yourself, immersed in that, you think, ‘Wow, I get to watch this little dinosaur do its thing.’ Those commonplace things are just amazing to me when I stop and think about it.”

Chandler agrees.

Even after years of tracking down nests and banding birds, Chandler says he’s still in awe when he spots a banded bird that shows a bird has been coming back to the site for many years. “These birds are migrating down to Central America, to the Antilles, Cuba, Jamaica, and some of them have done the roundtrip eight times or more. It’s just phenomenal to see it,” he says. “Every spring it’s amazing to see these birds come back, and hopefully our research will help ensure that we conserve migratory birds for future generations.”

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