EVIDENCE FOR REVERSE MIGRATION IN RED KNOTS, CALIDRIS CANUTUS RUFA, (SCOLOPACIDAE) DURING NORTHWARD MIGRATION IN PATAGONIA.

D'AMICO VL; GONZÁLEZ PM; MORRISON, RIG; BAKER AJ

Vancouver

Congreso; IV Western Hemisphere Shorebird Group Meeting; 2011

As part of the project ?Monitoring of the Red Knot at five sites in Argentina?, colour-marked individuals were monitored annually during their northward migration. This allowed us to investigate movements of birds between two major stopover sites in Patagonia: Península Valdés (Chubut) (PV) and San Antonio Oeste (Río Negro) (SAO), 192 km north of PV. Monitoring of birds captured and colour marked at various sites in the western Atlantic flyway, including SAO, was carried out between February and May from 2006 to 2010 at both sites. In this 5 year period, 75 different individual knots were detected moving from SAO to PV representing 43% of the 175 individuals observed there, but only 2.6% of the 2835 individuals resighted or caught in SAO. Approximately 13% of the detected individuals moved from SAO to PV in more than one year of the study. The southwards movements of individually marked knots from SAO to PV occurred in all years of the study; 27 of 79 (34%) occurred in 2006, 17 of 45 (38%) in 2007, 5 of 22 (23%) in 2008, 9 of 30 (30%) in 2009 and 33 of 69 (48%) in 2010. One Red knot was observed in SAO and PV the same day in 2009. These observations demonstrate the annual occurrence of flights of about 200 Km in the opposite direction to the normal northwards migration, and can be considered the first documented example of ?reverse? migration in Red Knots in the western hemisphere flyway. We discuss the possible causes of this behavior.