The Almost Impossible Mission of Studying the Lesser Yellowlegs

Essentially the most distinctive function of the Lesser Yellowlegs (Tringa flavipes) is its brilliant yellow legs, which give it its widespread title. Nonetheless, its most spectacular attribute is the flexibility to fly greater than 4,000 kilometers in 4 days. Sure, that’s roughly a thousand kilometers a day, normally flying in flocks.

Now, let’s speak about one other trait: being virtually a grasp at evading mist nets. This has been confirmed, with a lot frustration, by Santiago Muñoz and Juan David García, two younger biologists who’ve spent a number of migratory seasons organising traps in rice fields throughout Valle del Cauca and Cauca—departments situated in southwestern Colombia—to seize these birds. After they succeed, in a race in opposition to time, they need to rapidly take away the birds from the nets, weigh and measure them, examine their total situation, and fix a small (virtually tiny, weighing 1.25 g—not more than 2% of the chook’s weight) radio transmitter, earlier than releasing them to proceed their journey throughout the hemisphere. Contemplating all that’s concerned, half an hour flies by.

However then comes the enjoyment of a job effectively completed. Santiago and Juan have spent whole days, generally earlier than daybreak, ready for a chook to fall into the online. Many occasions (greater than they wish to admit), they solely catch dragonflies. So, after the adrenaline rush of attaching the radio transmitter to the chook’s again, they return dwelling with the satisfaction of a mission achieved.

And the enjoyment of that day solely grows when, due to the radio transmitter and the Motus Wildlife Monitoring System, they will see that Cholao —the final tagged Tringa, named after a conventional dessert from the area the place it was captured—weighing 113 grams (with a mean weight between 65 and 115 grams), measuring 24 to 30 cm in size, and with a wingspan of fifty to 60 cm, has flown all the way in which to Texas, the place it was detected by the tower situated at Rockport Bay Training Middle.

The trail traced by Cholao’s transmitter seems as a straight line between Colombia and the USA, passing by Panama, Costa Rica, Nicaragua, Guatemala, and a part of Mexico. If Cholao had been detected throughout that four-day interval, or afterward, by one other MOTUS tower—which has a detection vary of fifty kilometers—it could have been attainable to be taught extra about its journey: whether or not it made stops, its flight altitude, and different particulars. But it surely wasn’t. With no additional detections, one may even imagine it didn’t survive the journey.

Tringa flavipes is taken into account a susceptible species by the Worldwide Union for Conservation of Nature, having misplaced 60–80% of its inhabitants within the final 50 years, based on the North American Fowl Conservation Initiative. It is listed as a species of conservation concern in the USA by the U.S. Fish and Wildlife Service and is assessed as threatened in Canada by the Committee on the Standing of Endangered Wildlife in Canada.

It belongs to the household Scolopacidae, which incorporates different shorebirds. It’s discovered primarily in North and Central America through the breeding season and migrates to South America for the winter. People that breed in Alaska and Canada migrate to wintering areas in South American nations, reaching so far as Patagonia.

The Lesser Yellowlegs feeds primarily on bugs, crustaceans, mollusks, and small fish, utilizing its lengthy, slender invoice to probe in mud and sand. It prefers moist habitats corresponding to swamps, marshes, seashores, and coastal areas throughout migration and breeding, which is why Santiago and Juan David hope to seek out them in rice fields—synthetic wetlands that, relying on their development stage, present shelter and meals for various chook species. Nonetheless, these ecosystems might be affected by human improvement and air pollution. The presence of birds like Cholao serves as an indicator of the well being of aquatic ecosystems, underscoring the significance of conserving wetlands and coastal areas.

Why is that this work in Valle del Cauca, Colombia, necessary? Over 80% of the wetlands that this species used have disappeared prior to now 50 years in Valle del Cauca. Rice cultivation supplies non permanent habitat for the survival of the Lesser Yellowlegs within the area. Audubon is working with the sugarcane sector to advertise crop rotation between sugarcane and rice, thereby offering habitat for this and different shorebird and waterbird species.

“Within the first seasons, we labored from 5:00 a.m. to five:00 p.m. We additionally tried 2:00 p.m. to 10:00 p.m., making an attempt to determine one of the best time to seize people, considering they won’t see the nets at night time,” says Santiago, whose favourite chook is Semnornis ramphastinus, the Toucan Barbet—a chook iconic to northeastern Ecuador and western Colombia, which he first noticed in a chook information.

Now, additionally honing the artwork of ready, the 2 biologists have lowered their working hours from 5:00 a.m. to 10:00 a.m. Their greatest day got here in 2022, through the first season they spent two months making an attempt to seize Tringas, in a joint effort with the Colombian NGO SELVA. Within the first few days, they caught two people. Then, on the final day of the season, they caught a gaggle of 11 people, eight of which have been tagged with radio transmitters. Fairly a feat!

That 12 months, a number of people, together with Cholao, made unbelievable flights to the U.S., based on information from MOTUS receiver stations. Nonetheless, after reaching the U.S., the alerts disappeared. These birds breed within the distant corners of the Boreal Forest in Canada and Alaska, a area wealthy in peatlands—a most popular nesting habitat for the Lesser Yellowlegs. What’s not plentiful, nevertheless, are MOTUS towers.

The worst season for Santiago and Juan David got here in 2023, once they didn’t seize even one particular person over 4 months of labor, 5 days every week. “We don’t know what occurred within the rice fields. We noticed many giant flocks passing by and have been making an attempt to refine our seize methodology. Though we did many exams, we achieved nothing, which was very irritating,” explains Juan David, whose favourite chook is the Entomodestes coracinus, the Black Solitaire, as a result of it was the primary chook he ever captured utilizing a mist web.

“Once we don’t catch something, we ask ourselves if we’re doing issues proper. So, we reached out to colleagues who do the identical work, and so they confirmed that the Lesser Yellowlegs is a really onerous chook to catch. They’re elusive, have good imaginative and prescient, are very clever, and on the similar time very calm. Others have tried several types of traps, at all times guaranteeing the chook’s well-being, and the outcomes are related,” says Santiago, explaining how tough their mission is.

The problem, along with the ready, is inserting the nets in areas with many people, as that will increase the possibilities of capturing extra birds. High-quality-tuning their eye to seek out synthetic wetlands, like rice fields, at their prime stage is actually a talent.

“Our work is step one in describing the migratory routes of people of this species that move by the geographic valley of the Cauca River, which has traditionally been a key migration hall, with excessive wetland density and essential stopover websites for shorebirds just like the Lesser Yellowlegs,” provides Santiago.

Regardless of the trouble—and the frustration of days with out outcomes—Santiago and Juan David say they love their work. It’s peaceable and requires lots of birdwatching, which they’re actually keen about. “There’s a lot we’d wish to be taught, which is why we hope to tag extra people and in addition obtain satellite tv for pc monitoring to collect rather more detailed details about their routes and contribute precious information to the conservation of migratory shorebirds that use these ecosystems. By understanding the websites, they go to to relaxation and feed, we will focus our conservation efforts on these locations.”

Early Outcomes and Learnings

Jorge Velásquez, Audubon’s science director for Latin America and the Caribbean, explains that “though few transmitters have been deployed on Tringa, proof reveals that the tagged people stay in Valle del Cauca all through their non-breeding interval. This means that the inhabitants arriving in Valle del Cauca spends the boreal winter within the valley, relatively than simply stopping over on the way in which to different areas. Subsequently, habitat administration efforts in rice fields and wetlands within the valley will considerably influence the inhabitants that winters there. It has additionally been documented that the Valle del Cauca inhabitants makes use of the mid-continental route throughout its northward migration, whereas it makes use of each the Atlantic and mid-continental routes throughout its journey south. This has allowed Audubon’s conservation work in Valle del Cauca to attach with broader conservation efforts in North America, corresponding to these at Audubon’s Riverlands Middle and Corkscrew Swamp.”