Migration of red knots on Kiawah-Seabrook Island-reference-data

The rufa Red Knot Calidris canutus rufa is a migratory shorebird that performs one of the longest known migrations among birds and has experienced a population decline of over 85% in recent decades. During migration, rufa Red Knots rest and refuel at stopover sites along the Atlantic Coast of the USA, including Kiawah and Seabrook islands in South Carolina. We document the importance of Kiawah and Seabrook islands forknots during their spring migration using on-the-ground surveys between 19 February and 20 May 2021 to record the occurrence and proportion of individually marked knots, as well as geolocators deployed on knots captured in the area. Using a superpopulation model, we estimated a minimum passage population of 17,247 knots (95% CI: 13,548–22,099; ~41% of the total rufa knot population) and an average stopover duration of 47 days (95% CI: 40.1–54.8). Our geolocator results showed that knots using Kiawah and Seabrook islands can bypass Delaware Bay and fly directly to the Canadian Arctic. Finally, our geolocators, combined with resighting data from across the Atlantic Flyway, indicate that a large network of more than 70 coastal sites concentrated largely in the southeastern USA provide stopover and overwintering habitat for the knots we observed on Kiawah and Seabrook islands. These findings show that Kiawah and Seabrook islands should be recognized as critical sites in the knot network and, therefore, a conservation priority. The threats facing these sites, such as prey depletion, anthropogenic disturbance, and sea level rise, require immediate attention.