The migratory strategies of the Red Knots using the Western Atlantic Flyway as revealed by geolocators

We define three migratory strategies of Red Knots Calidris canutus rufa in the Western Atlantic flyway using light-sensitive geolocators, illustrating the information geolocators can provide. From 2009 to 2014, geolocators were deployed on Red Knots at several stopover and wintering sites. Rufa Red Knots using the Western Atlantic Flyway have three main wintering regions: southern USA and the Caribbean Islands, northern Brazil, and southern South America. Knots from the Tierra del Fuego wintering population used a more predictable, less variable selection of stopover sites compared to the other wintering populations. They stopped at San Antonio Oeste, Argentina, on the north coast of South America, and then Delaware Bay on the north-eastern seaboard of the USA. Most of the Knots (>88%) fitted with geolocators that wintered in both southern and northern South America stopped in Delaware Bay on their northbound migration, whereas less than 50% of the Knots that wintered along the US east coast or Caribbean did so. Over 90% of all Knots in the Western Atlantic Flyway stopped in southern Hudson Bay and/or James Bay in Canada before going on to their Arctic breeding grounds. Data from geolocators provide context on the importance of Delaware Bay for all three wintering populations, shed light on its importance for long-distance migrants, and provide key information on the importance of the timing of the Delaware Bay stopover. They also reveal the birds’ success in reaching their Arctic breeding grounds, as well as providing information on incubation schedules and nesting success.