Post‐breeding migration and connectivity of red knots in the Western Atlantic

• Published in: The Journal of Wildlife Management
• Main Authors: Lyons, James E., Winn, Bradford, Keyes, Timothy, Kalasz, Kevin S.
• Other Authors: Georgia Department of Natural Resources and Manomet
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Argentina; Calidris canutus
• Online Access: http://dx.doi.org/10.1002/jwmg.21389; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjwmg.21389; https://onlinelibrary.wiley.com/doi/full/10.1002/jwmg.21389

ABSTRACT Red knots ( Calidris canutus rufa ) have 3 distinct nonbreeding regions: 1 in the southeastern United States and Caribbean, another on the northeast coast of Brazil in the Maranhão region, and a third along the Patagonian coasts of Chile and Argentina. Effective conservation and recovery of this threatened long‐distance migrant will require knowledge of population structure, migration ecology, and abundance and distribution throughout the annual cycle. We conducted a stopover population and biogeographic assessment of knots at the Altamaha River Delta, Georgia, an important stopover area in the southeastern United States. We estimated stopover population size and stopover duration during post‐breeding migration in 2011 at the Altamaha study area using mark‐resight data, and we inferred nonbreeding regions for this stopover population using stable isotope ratios of carbon and nitrogen in feathers, and observations (sightings and captures) during boreal winter from across the hemisphere. With an integrated Bayesian analysis of all these data, we also estimated the number of birds in the southeastern United States and northern Brazil during boreal winter. For mark‐resight analyses in Georgia, we made observations of marked individuals during 14 weeks from early August to early November 2011 and detected 814 individually marked birds. We used the Jolly‐Seber mark‐recapture model and estimated the southbound passage population at approximately 23,400 red knots. In ongoing studies elsewhere, isotope samples were collected from 175 (21%) of the 814 birds detected in our study, and ≥1 sighting or capture record during boreal winter was located in data repositories for 659 birds (81%). Isotopic signatures and boreal winter records indicate that the majority (82–96%) of the birds that stopped at the Altamaha Delta spend the boreal winter in the northern part of the nonbreeding range (southeast USA, Caribbean, and northern Brazil). Knots migrating to the southeastern United States, Caribbean, or Brazil remained on ...