The sandy beaches in the Atlantic Ocean on the northern coast of Uruguay, near the border with Brazil, are part of one of the world’s most unique ecosystems. This ecosystem of sandy beaches extends for more than 310.6 miles, from La Coronilla, in southern Uruguay, to the state of Santa Catarina, in southern Brazil. These beaches are characterized by a very narrow intertidal zone of only a few meters. This feature differentiates this area from many sites on the Red Knot (Calidris canutus) migration route, where the width of the intertidal area can extend for several kilometers. To understand how these shorebirds are using these narrow intertidal beaches, partners from Manomet, Fundación Lagunas Costeras, and the Centro Universitario Regional del Este de Uruguay are studying this and other questions through field studies in Uruguay and southern Brazil.
Thirteen years ago, the Chuy bar in northern Uruguay was known because hundreds of dead Red Knot individuals (Aldabe et al. 2015) were found at this staging area. Later, thanks to monitoring work on the beaches of Uruguay and southern Brazil covering about 28 miles during March and April of 2009, 2010, and 2011, it was found that more than 1,000 individual Red Knots migrating northwards use these beaches. It is estimated that each individual stays two to five days during their migration from southern Patagonia to their wintering grounds in the Arctic tundra. The Chuy was in the news again in April 2010 when the individual identified as YOY was recorded and became famous because it flew almost 5,000 miles to Delaware Bay, on the east coast of the United States, in only six days, as reported by researchers in the Wader Study journal (Niles et al. 2010).
Map from: Aldabe, J., Rocca, P. I., González, P. M., Caballero-Sadi, D., & Baker, A. J. (2015). Migration of endangered Red Knots Calidris canutus rufa in Uruguay: important sites, phenology, migratory connectivity and a mass mortality event. Wader Study, 122(3), 221–235. https://doi.org/10.18194/ws.00024
The beaches of Chuy bar are unique because they have wider intertidal and swash than the rest of the beaches in Uruguay. The swash zone (which is part of the intertidal) is the area of the beach between the wave breaker and the limit of wave ascent. This area is widely used by Red Knots for feeding. Perhaps for this reason, Chuy bar is the most important site in the country for Red Knots.
To understand if Red Knots prefer a wider intertidal area and to assess threats and monitor the species, we returned to the site in 2021 with Sasha Hackembruck, a young woman who lives in the town of Hermenegildo (Brazil), a few meters from the beach. Sasha studies Environmental Management at the University of the Republic of Uruguay and has participated in several research projects and shorebird conservation in the area. On this visit, we found several groups of birds feeding. In total, we recorded about 150 individuals of Red Knots, which is an interesting number for a population that passes through between March and April and only uses the site for a few days. But perhaps the most interesting result was that we could verify that the Red Knots did not use the entire beach equally. The birds preferred the sites with wider swash widths (even though they are very small in Uruguay). Narrow swash occurs where the beach is quite steep and where the waves break closer to the shore, making it difficult for the birds to find food.
Red Knots at The Barra del Chuy, Uruguay. Photo: Joaquín Aldabe.
This work allowed us to learn more about the Red Knot and how it uses this part of the world. In particular, we learned that the species do not completely use the vast Atlantic coast from Uruguay to Lagoa do Peixe in Brazil, but only those parts with a slight slope and large swash width. This information is of great value for prioritizing conservation areas in the chain of sandy beaches of Uruguay and southern Brazil, a very important migration stopover for Red Knot and other shorebird species.
For more information on these field studies in Uruguay and southern Brazil, please contact Joaquín Aldabe, Ranching and Shorebird Conservation Specialist at the Western Hemisphere Shorebird Reserve Network Executive Office, Manomet.
Cover Photo: Flock of Red Knots at the Barra del Chuy, Uruguay. Photo: Joaquín Aldabe.
