Red Knot (Calidris canutus) are a species of high conservation concern throughout the Americas, especially the rufa subspecies, which winters primarily along the Atlantic coast from the southern United States to Tierra del Fuego. The population of this subspecies has declined dramatically over the past twenty-five years.
During northward migration, many rufa Red Knots stop in Delaware Bay to feed on the eggs of horseshoe crabs, fattening up for the flight to the Arctic breeding grounds. Over the last 20 years, counts in Delaware Bay have fluctuated between 12,000 and 30,000 birds. However, in 2021 just under 7,000 Red Knot were recorded in Delaware Bay, increasing the already strong concern regarding the conservation status of this species.
One potential cause of this decline is the overall population of the species declining significantly from one year to the next from the many threats they face. However, another potential cause could be the permanence of large numbers of Red Knots in non-breeding areas of South America, a phenomenon known as over-summering.
Thanks to the support of Environment and Climate Change Canada, and Manomet individual donors significant efforts have been focused during the past few months on monitoring the population of the species in key sites in South America, in order to gather information about the presence and abundance of Red Knots in non-breeding areas during the austral winter. We have been working with several partners to coordinate and support simultaneous surveys of Red Knot at key sites in Brasil, Uruguay, Argentina, and Chile. A first stage of simultaneous surveys, aimed at the search for over-summering individuals, was carried out during the southern winter. Nine main areas were visited by more than 20 surveyors, but not many birds were found. The highest single-day count was in Brazil (444 birds in the Rio Grande do Sul area, on July 25th), followed by a second highest single-day count of 322 birds in Argentina (Faro Querandí area, Buenos Aires province, on July 19th).
Left: group of rufa Red Knots. Photo: Natalia Martínez Curci. Right: Surveys to search for overwintering individuals were carried out during the month of July 2021. Photo: Fernando Faria.
A second stage of simultaneous surveys carried out by our partners in the same key areas was just concluded in the past weeks, this time aimed at the search of migrating Red Knots during the austral spring. The results of these surveys are still being compiled, but we can anticipate that large abundances of Red Knots have not been recorded at any of the sites surveyed during the austral spring.
Efforts to learn more about the current population status of Red Knots subspecies rufa will continue in the coming months. The monitoring work during the austral summer will focus on the following sites in Argentina: Reserva Costa Altántica (Tierra del Fuego, Argentina), Estuario del Rio Gallegos (Santa Cruz, Argentina) and Estuario de la Bahía Blanca and surroundings (Buenos Aires, Argentina). Significant efforts will also be made in Bahía Lomas (Chile), which is one of the most important wintering sites for the rufa subspecies in South America and where monthly aerial surveys will be carried out between January and March 2022.
Because little is known about the abundance and distribution of the subspecies during its migration to the north, the monitoring will continue during the austral autumn (March-April 2022) in those sites considered key for the migration of the species.
We hope that these coordinated and large-scale efforts will allow us to understand the status of the species, the sites where it is concentrated in greatest numbers throughout its stay in South America, obtain more information about the current status of its population, and potentially identify the main causes of this recent decline. With this information it will then be possible to identify and support those actions that will aide in recovery.
Cover Photo: Group of Red Knots on the coast of the state of Rio Grande do Sul, Brazil. Photo: Fernando Faria.
