The predawn darkness of Jamundí, Colombia, offers little visual guidance, yet beneath a sky still painted in hues of charcoal and indigo, a landscape emerges as a kaleidoscope of molten-silver puddles—the flooded rice fields of the Cauca Valley. This is where the chase begins, not for profit or sport, but for science, for understanding, and ultimately, for survival. Here, where vast expanses of sugarcane and rice stretch towards the horizon, punctuated only by the occasional silhouette of bamboo, palm, and kapok trees, a dedicated team of biologists embarks on a crucial mission. Santiago Muñoz Bolaños and Juan David García Uribe, biologists from Icesi University in nearby Cali, along with four colleagues, pull on their gumboots, cover their faces with neck gaiters to fend off swarms of insects, and march towards these shimmering agricultural wetlands, guided by the faint red glow of headlamps designed to deter mosquitoes.
Their destination is a carefully chosen capture site, reached by navigating the mushy dikes that crisscross the fields. As the first hints of daylight begin to pierce the darkness, the team unfurls delicate mist nets, their almost invisible mesh poised to snare their elusive targets. To avoid disturbing the birds, they quickly retreat to their makeshift workstation: a modest setup of two plastic chairs and a table, sheltered by a tiny canopy tent that provides scant protection from the persistent light drizzle, which itself seems to dampen the morning chorus of ibises, Black-necked Stilts, and distant roosters. Then, they wait. Every twenty minutes, they take turns traversing the slippery dikes back to their nets, a silent vigil maintained in the hope of finding one particular bird tangled in the fine mesh: the Lesser Yellowlegs.
A Hemispheric Journey and a Precarious Existence
The Lesser Yellowlegs (Tringa flavipes) is a marvel of avian endurance, a slender shorebird that undertakes one of the most remarkable migrations on Earth. Each year, these birds journey thousands of miles, departing from their remote nesting grounds in the boreal forests and tundra of Canada and Alaska. Their epic southbound migration carries them across vast stretches of North America, Central America, and the Caribbean, culminating in their nonbreeding sites – a mosaic of marshes, wetlands, and even agricultural fields – stretching from the southern United States all the way to the southernmost tip of Patagonia. This incredible migratory feat, however, is increasingly imperiled. These far-flung migrants are currently at a critical tipping point, facing a precipitous decline that has seen their global population shrink by more than 60 percent over the past five decades. The last ten years, in particular, have witnessed alarming steep declines, driven primarily by the relentless conversion of their vital nonbreeding grounds into agricultural land, alongside other human-induced pressures.
The Cauca Valley, a region of immense biological richness in western Colombia, represents a crucial wintering destination for these birds. Despite covering a mere 2 percent of Colombia’s national territory, the valley is a biodiversity hotspot, hosting hundreds of the nearly 2,000 avian species documented across the country. Yet, this ecological treasure trove has been under severe assault for decades. Since the 1970s, the region has suffered an estimated 80 percent loss of its natural wetlands and forests. This environmental degradation is largely attributable to the expansion of industrial sugarcane cultivation, extensive cattle ranching, and unchecked urban sprawl. The consequences have been dire: at least 18 aquatic bird species have faced local extinction in the twentieth century alone within the Cauca Valley. As Gloria Lentijo, Audubon’s director of regenerative agriculture for Latin America and the Caribbean, starkly puts it, "This is a landscape that is highly threatened."
The Pursuit of Knowledge: A Chronology of Research
Understanding how Lesser Yellowlegs utilize the fragmented and altered landscapes of the Cauca Valley is paramount to their conservation. In response to this urgent need, Audubon researchers initiated a collaborative project with local scientists from Icesi University and the conservation organization Calidris in 2022. The primary objective was to determine if managed agricultural lands, particularly rice fields, could serve as a viable proxy for the natural wetlands that have largely vanished from the region.
The project’s initial phase in 2022 involved traditional methods: attaching radio transmitters to 25 Lesser Yellowlegs. To monitor their movements, the team erected seven towers equipped with antennae capable of detecting when a tagged bird passed within range. While this provided valuable broad-scale data, the researchers recognized the need for more granular, real-time information to truly unravel the mysteries of the birds’ behavior and migratory patterns.
November 2023: A Technological Leap Forward
A significant advancement occurred in November 2023, marking a new chapter in the research effort. For the first time, the team successfully equipped several birds with state-of-the-art GPS trackers. Unlike the earlier radio transmitters, these compact devices report location data in real time, from virtually anywhere on the globe. This technological leap promised to unlock unprecedented insights into the Lesser Yellowlegs’ lives. The detailed data generated by these trackers is expected to shed light on long-standing questions about their migration paths, such as whether they undertake arduous, non-stop ocean crossings or if they make crucial stopovers on islands along the way.
Crucially for conservation efforts within the Cauca Valley, the GPS data also provides vital information on the birds’ wintering habits. Researchers hope to determine if individual yellowlegs consistently return to the same specific locations each winter and, critically, how heavily they rely on the agricultural rice fields for foraging and roosting. "Knowing where yellowlegs go is key to ensuring their survival," emphasizes Gloria Lentijo. However, acquiring this essential data has proven to be anything but simple, requiring immense patience, ingenuity, and resilience from the field team.
Learning to Wait: The Art of the Catch
The challenge of catching a Lesser Yellowlegs is a testament to the species’ acute senses and wary nature. "We’ve come up with so many strategies," recalls Juan David García Uribe, recounting the team’s often frustrating learning curve. For most diurnal bird species, researchers typically deploy mist nets in areas known for early morning bird activity. However, the keen eyesight of the yellowlegs allowed them to easily detect and avoid the nets placed at the edges of the rice fields. The team experimented with varying the number and position of the nets, to no avail. They shifted their efforts to the dead of night, only to find themselves catching bats instead of shorebirds. Weeks were spent painstakingly hand-sewing nylon strings onto 40 Styrofoam boards to create elaborate carpet traps, which, despite the effort, snared exactly zero birds.
The nadir of their efforts came in 2023, after months had passed without a single successful capture. Despite observing a large flock feeding in a rice field, they simply could not get close enough to catch any. Driven by desperation, they devised an elaborate ambush plan. At dusk, two team members would crawl, military-style, through a vulture roost—a less-than-pleasant environment caked in droppings—towards the birds to flush them. Simultaneously, two other colleagues would close 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, surprisingly, flushed exactly as anticipated, heading directly towards the net. Yet, at a mere three feet away, they veered off, disappearing into the twilight. "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 recounts, highlighting the often-unglamorous realities of fieldwork. The second season concluded with no birds tagged.
Frustration led to seeking external expertise. Local farmers, intimately familiar with the land, advised them that the optimal time for capturing shorebirds was after the rice harvest, when tractors churned the wet soil and left it to rest. Colleagues from Audubon California provided invaluable guidance, suggesting a renewed focus on morning captures and supplying them with realistic decoys. García and Muñoz meticulously hand-painted these decoys, which they now strategically nail into the mud near the nets. During their most recent season, another crucial piece of advice came from River Gates, Audubon’s Pacific shorebird conservation initiative coordinator: the audio recording they had been broadcasting over speakers was an alarm call, inadvertently scaring the birds away. The group promptly swapped it for a different call, designed to lure rather than repel.
While there is still no guarantee of catching yellowlegs every time, these adaptations have significantly improved their success rate. On a crisp November morning, around 7 a.m., undergraduate student Esteban Ramos, visiting from Universidad Surcolombiana, returned from checking the nets cradling a wriggling burgundy cloth bag. Inside was the first Lesser Yellowlegs of the outing. The makeshift workstation sprang to life, transforming into a well-oiled tagging operation.
River Gates, the source of the alarm call tip, carefully weighed the bird: 63 grams, or approximately 2.2 ounces. "How are we going to name you? Not Marranita because there’s no fat on you," García quipped, referencing a traditional Colombian snack of fried plantains and pork. Muñoz then meticulously measured various body parts—beak, head, tarsus, wingspan—while García diligently recorded every detail. "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 explained, underscoring the preciousness of each capture. A GPS tracker was carefully affixed to the bird’s back. Black and yellow beads were slid onto one leg, serving as a visual indicator of the tagging country, and a silver band engraved with a unique identification number was placed on the other. With the data collected and the tracker secured, the bird was gently released back into its habitat.
During that single outing, the team successfully affixed GPS trackers to five birds. The initial results have already begun to dramatically redraw the team’s assumptions about how these migratory birds utilize the valley’s landscape. "When I saw the tracked information from the GPS tags, it was like a light bulb went off in my head," exclaimed Jorge Velásquez, Audubon’s science director for Latin America and the Caribbean. Prior to this data, the prevailing assumption was that the birds would primarily concentrate in the natural wetlands surrounding the Cauca River. However, when the location data from the GPS trackers was plotted, it revealed a startling truth: the rice fields of Jamundí actually exhibited the highest density of bird activity. "Those maps were a revelation," Velásquez confirmed.
Changing the Landscape: Innovative Conservation Models
The revelations from the tagging project arrive at a profoundly critical juncture for the Cauca Valley. The rapid shift in land use, from natural ecosystems to intensive agriculture and urban development, is a phenomenon Muñoz and García have witnessed firsthand. They have tagged birds on approximately a dozen different rice farms since the project’s inception. Alarmingly, at least one of those sites has since been converted into an apartment complex, while another has switched from rice cultivation to sugarcane, which is generally less labor-intensive and therefore more profitable for landowners. García, with a touch of dark humor, summarizes the grim reality: "The natural ecosystem cycle here is from wetland to rice crops, to sugarcane, to houses."
To address these escalating threats, Audubon launched its first working lands program in Latin America in the Cauca Valley four years ago, around 2020. This ambitious initiative aims to promote bird-friendly agricultural practices, including habitat restoration and silvopasture (integrating trees with pastureland), across more than 860,000 acres in the valley. The overarching goal is to create a more hospitable landscape for both migratory and local bird species. "The Cauca Valley is a laboratory to test approaches," Lentijo explains, highlighting its role as a proving ground for scalable conservation solutions.
A cornerstone of this effort is a pioneering partnership between Audubon, Calidris, Icesi University, and the Arrocera La Esmeralda-Arroz Blanquita rice mill. This collaboration focuses on studying the potential of a sugarcane-rice rotation pilot program for waterbird conservation. Sugarcane, after six or seven harvests, experiences a steep decline in yields, necessitating the removal of existing plants and replanting. It is at this crucial juncture that Blanquita intervenes, suggesting the cultivation of rice for one or two cycles. This creates temporary wetlands that serve as vital stopover points or winter homes for migratory birds. The practice offers multiple benefits: flooding the fields helps to control pests, allows the soil to rest and recuperate, and the fast-growing rice crops provide producers with a quick cash injection. Pilot studies have already demonstrated that this model can increase farm productivity by at least 20 percent, presenting a compelling case for its adoption.
Economic Viability Meets Ecological Imperative
So far, farms have enrolled a combined 2,500 acres in the crop rotation pilot program. However, participation is not constant, and not all farmers join every year. Lentijo notes that if sugarcane prices are high, fewer producers opt into the rotation. Expanding the number of participating farms has also been a gradual process. The sugarcane industry in the region is highly mechanized and inherently risk-averse, accustomed to making decisions based on robust scientific data. "They like to make decisions based on scientific data," Lentijo reiterates, emphasizing the need for concrete evidence to drive change.
Despite these challenges, momentum is steadily building. Audubon, Calidris, and Cenicaña, the sugarcane industry’s research center, have collaboratively developed a comprehensive playbook providing practical recommendations for sugarcane farmers to support avian biodiversity. The next step involves creating "demonstration farms" where farmers will implement these bird-friendly practices, allowing for shared knowledge, peer-to-peer learning, and further study of the ecological and economic impacts.
Crucially, the detailed data gleaned from the Lesser Yellowlegs tagging project directly informs these outreach efforts. "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 asserts. This scientific evidence provides a powerful argument for conservation, illustrating the tangible connection between agricultural practices and the survival of migratory species. Safeguarding these critical nonbreeding grounds in the Cauca Valley gives the Lesser Yellowlegs a significantly better chance to thrive, not only in this specific region but across its entire hemispheric range, effectively removing one of the many formidable obstacles the species confronts throughout its arduous migration.
Resilience and the Path Forward
Approximately a year ago, Santiago Muñoz Bolaños, one of the leading biologists in the project, got a tattoo of a Lesser Yellowlegs on his right arm. It is a permanent tribute to a bird that has taught him profound lessons. If these resilient shorebirds have imparted any wisdom, Muñoz reflects, it is the capacity to relentlessly find a way forward through a landscape that is constantly shifting and changing underneath them. "We now see problems as a chance to find a solution," he states, embodying a spirit of adaptive optimism. "You just have to try to find it."
The work in the Cauca Valley represents a microcosm of global conservation challenges and opportunities. It underscores the critical importance of interdisciplinary collaboration, the power of technological innovation, and the necessity of engaging local communities and industries in sustainable practices. As the Lesser Yellowlegs continues its epic migrations, its survival hinges on the continued dedication of scientists like Muñoz and García, and the broader willingness of humanity to adapt its landscapes for a shared future. The silver puddles of Jamundí, once just rice fields, are slowly being recognized as vital sanctuaries, beacons of hope for a species teetering on the brink, and a testament to the enduring power of scientific discovery and collaborative action.
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.
