A Bird in the Hand
Studying a Texas Specialty
Every golden-cheeked warbler is Texan born and bred — the only place in the world that these birds lay eggs is Central Texas. Each spring, the whole population migrates from their winter home in far southern Mexico and Central America up north to Texas’ Edwards Plateau to find a mate and raise the next generation. Because humans, too, are flocking to this region, the warbler has competition. Research on the bird helps us monitor how it is adapting.
Texas State’s Freeman Center is a research facility composed of about 3,500 acres of ranchland, located in San Marcos within the warbler’s range. While this particular land had not been considered a notable location for the golden-cheeked warbler, in the last few years there have been sightings of the bird here. So biologist Rebekah Rylander, a doctoral researcher, set up a scientific study. Beginning in March when the migration usually starts, she waits and watches for the warbler.
“A few years ago, we realized the bird was on the property, but we didn’t know anything about it: what habitat it was using, how many of them, whether the ranch land management practices were affecting it.”
It’s crisp and clear when we arrive at the Freeman Center headquarters at about 8:30 a.m., and quiet. Apparently, most researchers are either already at work elsewhere on the ranch, or not here yet; the activity around the headquarters consists of several cows grazing freely. We’re here in hope of finding one of two golden-cheeks that Rylander’s team spotted two and three days ago.
As we head off into the ranch interior, Rylander explains the origin of her warbler research. “A few years ago, we realized the bird was on the property, but we didn’t know anything about it: what habitat it was using, how many of them, whether the ranch land management practices were affecting it.” To gather this information, she began doing surveys for the warbler in 2017, with the help of a series of undergraduate volunteers. They walk along transects — straight lines defined through pieces of the ranch — looking and listening for signs of the bird. If they find one, they note down the precise location, and Rylander tries to gently capture it in order to place an ID band on its leg. Once a bird is banded, the researchers can develop a record of that individual’s habits, such as which places make up its unique territory.
Finding a warbler on the ranch is a little like finding a needle in a haystack. The brush is thick and the bird is small, less than five inches from beak to tail-tip. Luckily, the male warbler’s song is distinctive. Rylander tells us that it sounds like the old folk song: “La cucaraCHA!” We make our way toward the place where the year’s first warbler was seen, following a fence line at first, stopping periodically to listen hard. In between these pauses, Rylander talks about the warbler’s biology.
Golden-cheeked warblers seek out large, unbroken stretches of habitat, including the Freeman Center but more commonly larger places like Fort Hood to the north, Camp Bullis to the southwest, and the Balcones Canyonland National Wildlife Refuge outside of Austin. The warblers seem to need each other as neighbors; they don’t exactly get along, but having a familiar (if annoying) face nearby is important to them, evidently. “These birds really like to sing against each other — it’s kind of like, ‘yeah man!’” says Rylander, putting on a macho-sounding voice to indicate the birds’ bravado. “They sing against each other all the time.” Because of this preference, golden-cheeked warblers need wild places that are big enough for multiple birds to stake out territories of around ten acres each.
With so many people living in and moving to Central Texas, wild places like that are getting chipped away through development. That’s what makes Rylander’s study important. Human-driven environmental changes could be altering the warbler’s range. “Is this piece of property, the Freeman Center, going to become a hotspot for the warblers?” Rylander wonders. “Sometime down the road, with development, this may become a critical habitat for them.”
Soon we leave the fence and dive into the scrub. There are no trails here; Rylander leads the way based on some GPS coordinates and either experience or intuition. There’s a lot of ducking under low branches, fending off whippy stems of vegetation, and watching our footing, all while carrying the equipment we’ll need if we’re lucky enough to find the bird: long poles to hold up a giant net, and a specialized tool kit for putting on the bands. As she bends around a tree, Rylander comments, “Friends tell me that I’d be really good at Twister.” She laughs. “When I train my undergrads, I take them to some pretty hairy habitat, and I’m like, ‘Let’s go!’”
At a clearing, we stop to check Rylander’s GPS unit. The more formal part of her undergrad surveyors’ training is in learning how to navigate with GPS, how to use aerial maps of habitat, and how to work responsibly with an endangered species. Since 1990, the golden-cheeked warbler has been listed as endangered in the United States, giving it protected status and requiring a variety of federal and state permits for researchers. Getting this experience as undergrads has helped Rylander’s team both before and after graduation, making them competitive for internships and other research opportunities.
“I learned skills that are crucial for a wildlife biologist.’’ — Alex Klingele, one of Rylander’s surveyors
Alex Klingele is a wildlife biology senior who’s been doing the warbler surveys with Rylander since 2018. “She provides a lot of opportunities for hands-on experience that is hard to come by, and certainly on a scale that no else does,” he says. “I learned skills that are crucial for a wildlife biologist, like using a combination of GPS and aerial view mapping to find a specific location. This played a huge role in landing my first wildlife job this summer. The navigation skills that the warbler surveys taught me was a deciding factor in my interview. Proving that I could navigate difficult terrain alone and had experience doing so made the interviewer more willing to take a chance.” After graduating in May, Klingele will head east to work on vegetation surveys with Penn State University. Other surveyors have found positions at the American Bird Conservancy, Texas Audubon, Texas A&M and more.
The warbler research also gives students a chance to make a local impact. Along with the Freeman Center survey, Rylander runs the same setup on San Marcos Parks and Recreation properties. Currently, city-owned trails in known warbler nesting territory are closed to human traffic from March through May, to avoid disturbing the birds during this important part of their lifecycle. It’s a balancing act: While respecting the birds’ personal space, we also want people to be able to experience the beautiful natural resources that make this area so appealing, especially during the spring wildflower season. By collecting data on the dates and locations that the birds are spotted, Rylander’s team provides valuable information for the city’s determination of when to close or open trails.
Back at the ranch, we hear a song that’s somewhat like, but not quite, the warbler’s. “That’s a white-eyed vireo — kind of like a remix,” Rylander notes. We also hear a Hutton’s vireo, a Bewick’s wren and a rufous-crowned sparrow. In the past, Rylander has seen coyotes and foxes during her surveys, and while she herself has never seen one, there have been cougar sightings at Freeman. Today, though, we see no mammals and, so far, no golden-cheeked warblers.
Most of the trees we’re trekking through are Ashe juniper — often colloquially called “cedar,” and hated by many people because of the intense allergies they provoke early in the year. Rylander points out the long strips of bark hanging from the nearest tree: “The warblers use the stringy bark to build their nests — if they don’t have old-growth juniper and oak, they won’t stay.” The same tree that is the bane of many Central Texans’ existence is essential for the warbler.
Male golden-cheeked warblers migrate in spring to establish a breeding territory to defend. If a female comes in and doesn’t find what she’s looking for — not the right trees? not enough warbler neighbors? — she moves on to another spot. The males usually follow. So far, Rylander has not banded any females at the Freeman Center. It seems like the inexperienced males, birds born the previous year who are now trying to breed for the first time, are the ones that end up at Freeman. The existing data shows that they stay for anywhere between one day to a couple of weeks. “This is pretty suitable habitat — that’s why we’re getting detections in these areas — but we’re just not sure why they aren’t sticking around,” Rylander says. “That’s part of why we’re doing the studies over a period of years.”
Rylander checks her phone for a text: In a different part of the ranch, wildlife biology senior Jenni Vanhoye has spotted a warbler.
This is Vanhoye’s first semester doing the warbler survey, but she’s worked with Rylander on other bird research for a couple of years. “I love going out and doing the surveys,” she says. “It’s a great excuse to go for a hike, and it’s a bit like a treasure hunt. The prize is to see this cute little warbler that is so special to Texas.”
With that prize glimmering in our mind's eyes, we venture further into the wilderness. Rylander is excited about this bird; she thinks that he’s likely to be an easy catch for someone like her who knows exactly what she’s doing and has the permits to prove it. At this point, she’s been working with the warbler for almost a decade. (And it’s not even her dissertation species. For her Ph.D. in aquatic resources and integrative biology, Rylander is studying the social structures of the black-crested titmouse; she has banded more than a thousand individuals since 2013.)
Describing the capture process, Rylander says, “It’s like this cat-and-mouse game. It’s really intense. I usually get an adrenaline rush.”
It’s warmer now — we’ve reached midday — and the sun is bright in a clear blue sky. Suddenly:
That was it, the song of a male golden-cheeked warbler. We stand stock-still, listening. It comes again: La cucaraCHA! La cucaraCHA! He’s close. Carefully, we move through the thicket, zeroing in on the bird’s location and looking for a somewhat clear-ish space among the brush to set up the net.
It’s called a mist net because of how fine the mesh is — nearly invisible here in the juniper woods. Rylander assembles two poles and hangs the net loosely between them, stretching it about 12 feet, at roughly head height. We move back several yards, crouched down low. The warbler is hopping around in the trees above us, either not noticing or not caring about our activity.
Rylander uses her phone to play a particular sound that catches the bird’s attention. He hops nearer, then retreats. For about five long minutes, this dance continues: Rylander’s eyes are fixed intently on the bird as he flits back and forth between the trees. Then, when the warbler makes his next dash, he flies into the net.
Rylander bolts over and gently closes her hands — shaking; the adrenaline rush is real — around the bird, protecting him from tangling in the threads of the net. With the bird in one hand, she sits down next to her banding tool kit and gets to work.
First, she selects a small silver band, issued to her by the government. It has an ID number engraved on it, which she writes down on a sheet of paper. She uses a tool to wrap this band around the warbler’s left leg, not too tight, not too loose. Next, she adds colored plastic bands: a light blue one on the left leg, white and yellow on the right. This bird now has a unique identification sequence, so that if he is seen clearly or recaptured by a permitted bander in the future, whether Rylander or another researcher, that person can add data to the bird’s record. Rylander is already writing down the GPS coordinates, the date, and her name as the bander. If she’s able to get further data, it will help her understand the size and location of this bird’s territory, the specific type of habitat he’s using, and the time periods that he’s using it.
Rylander gently examines the bird’s wing. The condition of the feathers on his wing and tail help her estimate his age: “This guy is young, it’s his first breeding season. He was born last year.”
After she has recorded her observations, Rylander opens her hand, and the warbler shoots away into the trees. He doesn’t go far, though; we can still see him above us, perched near the top of a tree, seeming to inspect his new bands. Although his face is a bold yellow-and-black pattern, it’s all too easy to lose sight of him momentarily as he moves through the leaves. Strikingly colored birds can indeed camouflage themselves. He looks bigger at the treetops than he did in Rylander’s hand.
We spend a long time admiring him, and then finally we leave the warbler to his own devices. He’ll spend the rest of the spring eating bugs and caterpillars, trying to attract a mate and hopefully contributing to a successful clutch of eggs. Then, come July, he’ll make a journey of some 1,500 miles to his winter home in Central America. Maybe Rylander will see him again next year when he comes back.