First results using light level geolocators to track Red Knots in the Western Hemisphere show rapid and long intercontinental flights and new details of migration pathways

Geolocators affixed to Darvic leg flags were attached to the tibia of 47 Red Knots Calidris canutus rufa during the 2009 spring migratory stopover in Delaware Bay, New Jersey, United States. We found no difference between the behavior of birds with and without geolocators in the weeks after release and saw a greater proportion of birds with geolocators than those with inscribed leg-flags a year after release. There were no significant differences in the resighting rate in Delaware Bay in the year of attachment or in places other than Delaware Bay during the ensuing twelve months. Three individuals were re-captured in May 2010 in Delaware Bay. All three birds flew to the Arctic, only one apparently bred, and all three wintered in South America. The longest roundtrip flight was 26,700 km, which included an 8,000 km, 6-day flight from southern Brazil to the coast of North Carolina. All three wintered away from the main sites thought to be used by the subspecies. Two birds appeared to detour around weather systems. These results suggest that geolocators are likely to afford valuable new insights to our understanding of Red Knot migration strategies as well as their breeding and wintering locations, and underpin their conservation.