Biologists Are Racing to Protect These Elusive Shorebirds. But First They Have to Catch Them

The chase starts when the rice field still looks like a kaleidoscope of molten-silver puddles under a pitch-dark sky. Here in Jamundí, sugarcane fields and rice crops stretch to the horizon, occasionally broken by stands of bamboo, palm, and kapok trees. Santiago Muñoz Bolaños and Juan David García Uribe, biologists at Icesi University in nearby Cali, pull on their gumboots, cover their faces with neck gaiters to defend from bugs, and march toward the silver splashes with four colleagues.

They stride through the mushy dikes, guided by headlamps blazing red light that attracts fewer mosquitoes, and stop at the capture site. They unfurl the mist nests as darkness gives way to daylight. So as not to spook their targets, they quickly retreat to their workstation: two plastic chairs and a plastic table under a tiny canopy tent, which barely keeps out the light drizzle that dampens the calls of ibises, Black-necked Stilts, and roosters. Then, they wait. Every 20 minutes, they take turns crossing the slippery dikes towards their nets, hoping to see one bird tangled in the mesh: the Lesser Yellowlegs.

The slender shorebirds migrate from nesting grounds in the boreal forests of Canada and Alaska to nonbreeding sites in marshes and wetlands stretching from the southern United States to Patagonia. These far-flung migrants are at a potential tipping point, having lost more than 60 percent of the species’ population in the past 50 years—and steep declines in the past decade have been driven largely by conversion of their nonbreeding grounds to agricultural land. 

Every year since 2022, Audubon researchers have teamed up with local scientists to catch the elusive birds in rice fields of the biologically rich Cauca Valley. They are hoping to understand if these managed lands can be a proxy for the wetlands that have largely disappeared in the region. In the project’s first years, the team attached radio transmitters to 25 yellowlegs and erected seven towers with antennae that detected when tagged birds passed nearby. Now, they’re harnessing more advanced technology to get more granular details about the birds’ whereabouts. 

Last November, for the first time, they equipped birds with GPS trackers that report location in real time, from anywhere. The detailed data may help solve mysteries about the birds’ migration paths, such as whether they traverse the ocean in one long flight or stop on islands along the way. The gadgets can also provide insights crucial for conservation in the Valley, like whether the yellowlegs return to the same places every winter and how much they rely on rice fields, says Gloria Lentijo, Audubon’s director of regenerative agriculture for Latin America and the Caribbean. Knowing where yellowlegs go is key to ensuring their survival—but getting that data has been no simple task.

Learning to Wait

To tag a bird, first you have to catch it. And Lesser Yellowlegs don’t make it easy. “We’ve come up with so many strategies,” García says.

With most diurnal species, researchers set up mist nets in an area they know the birds fly through in the early morning. But yellowlegs, with their sharp eyesight, easily dodged the mist nets they set up on the edges of rice fields. The researchers tried changing the number and position of nets. No luck. They switched to the dead of night but only caught bats. They spent weeks hand-sewing nylon strings onto 40 Styrofoam boards to create carpet traps that snared exactly zero birds.

Their most desperate plan came in 2023, when months had passed without a single catch. They’d seen a big group eating on a rice field, but they just couldn’t get them in hand. So they devised an elaborate ambush: At dusk, two people would crawl, military-style, through a vulture roost caked in droppings toward the birds to scare them, while two others closed in from the opposite direction with nets. “On paper, it was a perfect plan. We were like, ‘Let’s patent this,’” jokes García. The birds flushed exactly as planned, headed straight for the net—and then, three feet away, veered off. “And there we were, with the car lights on, because it was already around 7 p.m., in our boxers, bathing in an agricultural canal, washing off the swamp. We discovered leeches that day,” García says. They ended the second season having caught nothing.

Frustrated, they sought outside help. Farmers told them that the best time to visit is after the harvest, when tractors churn the wet soil and leave it to rest. Audubon California colleagues taught them to focus on mornings and supplied them with decoys, which García and Muñoz hand-painted and now nail into the mud close to the net. During their last season, another colleague informed them the recording they’d been playing over speakers was an alarm call, so the group swapped in a different call that would better lure the birds.

There’s still no guarantee they’ll catch yellowlegs every time, but they see far greater success these days. Around 7 a.m. on this November morning, undergraduate student Esteban Ramos, visiting from Universidad Surcolombiana, comes back from the nets cradling a wriggling burgundy cloth bag: the first Lesser Yellowlegs of the outing. The makeshift workstation becomes a well-oiled tagging operation.

River Gates, Audubon’s Pacific shorebird conservation initiative coordinator (and the one who gave them the tip about the alarm call), weighs the bird: 63 grams, or 2.2 ounces. “How are we going to name you? Not Marranita because there’s no fat on you,” says García, referring to a traditional snack of fried plantains and pork. Muñoz measures various body parts—beak, head, tarsus, wingspan—while García writes everything down. “Since it is so difficult to capture each bird, we gather as much information as possible in the shortest time possible, even if we’re not going to use it,” Muñoz says. The team attaches a GPS tracker to the bird’s back, slides black and yellow beads on one leg to indicate the tagging country, and places a silver band engraved with a unique ID on the other leg. Then they release the bird.

During the outing, the team affixed GPS trackers to five birds. The results so far have already redrawn the team’s assumptions of how birds were using the valley. “When I saw the tracked information from the GPS tags, it was like a light bulb went off in my head,” said Jorge Velásquez, Audubon’s science director for Latin America and the Caribbean. They had assumed the birds would concentrate in the Cauca River and its natural wetlands. When they plotted the location data, however, they discovered the rice fields of Jamundí actually had the most bird activity. “Those maps were a revelation,” Velásquez says.

Changing the Landscape

The information arrives at a critical moment. Despite covering a mere 2 percent of the nation’s territory, the Cauca Valley is home to hundreds of the nearly 2,000 avian species documented in Colombia. But since the 1970s, the region has lost 80 percent of its natural wetlands and forests mainly to sugarcane, cattle ranching, and urban sprawl, causing the local extinction of at least 18 aquatic bird species in the twentieth century. “This is a landscape that is highly threatened,” says Lentijo.

Muñoz and García have seen the rapid shift happening in front of their eyes. They have tagged birds on around a dozen rice farms since the project started. At least one site is now an apartment complex, and another switched from rice to sugarcane, which is less labor-intensive and therefore, more profitable for landowners and farmers. “The natural ecosystem cycle here is from wetland to rice crops, to sugarcane, to houses,” says a half-joking García.

To address these threats, four years ago Audubon launched its first working lands program in Latin America here. The goal is to promote bird-friendly practices like habitat restoration and silvopasture across more than 860,000 acres in the Cauca Valley to support migratory and local species. “The Cauca Valley is a laboratory to test approaches,” Lentijo says.

As part of the effort, Audubon, the conservation organization Calidris, and Icesi University partnered with the Arrocera La Esmeralda-Arroz Blanquita rice mill—which had already implemented a sugarcane-rice rotation pilot program—to study the potential of this approach for waterbird conservation. After six or seven harvests, sugarcane yields steeply decline, so growers need to remove the plants and start over. That’s when Blanquita comes in and suggests planting rice for one or two cycles, creating temporary wetlands that birds can use for stopovers or winter homes. Flooding the fields also kills potential pests and allows soil to rest, while fast-growing rice crops offer producers a quick cash injection. Pilot studies have shown the model can increase farm productivity by at least 20 percent.

 So far, farms have enrolled a combined 2,500 acres in the crop rotation pilot, but not all farmers join every year. If sugarcane prices are high, fewer producers enroll, Lentijo explains. Expanding the number of participating farms has also been a slow process. Here, the sugarcane industry is highly mechanized and risk-averse. “They like to make decisions based on scientific data,” Lentijo says.

Yet momentum is building. Audubon, Calidris, and Cenicaña, the sugarcane industry’s research center, collaborated on a playbook providing recommendations for sugarcane farmers to support birds. They’re hoping to create “demonstration farms” where farmers will implement the playbook’s bird-friendly practices to share knowledge and study impacts.

Meanwhile, the data from the Lesser Yellowlegs tagging project also helps inform the groups’ outreach. “We now have much more convincing data to knock on farmers’ doors and say, ‘Hey, these places are important to birds; let’s work together,’” Velásquez says. Safeguarding these nonbreeding grounds gives the birds a better chance to thrive not just in this valley but across the hemisphere, removing one of the many obstacles the species faces throughout its long migration.

About a year ago, Muñoz got a tattoo of a Lesser Yellowlegs on his right arm. If these birds have taught him anything, Muñoz said, it is the ability to keep finding a way through a landscape that keeps shifting underneath you. “We now see problems as a chance to find a solution,” he said. “You just have to try to find it.”

This story originally ran in the Summer 2026 issue as “To Catch a Yellowlegs.” To receive our print magazine, become a member by making a donation today.