Abstract

The red knot Calidris canutus, a flagship migratory waterbird species, continues to decline within the Americas. One major unanswered question is the status and connectivity of birds spending the non-breeding season on the southern Pacific coast of South America. Answering this question will provide a useful geographic endpoint that could enhance ongoing conservation efforts. Red knots on Chiloe Island (43 degrees S, Chile) were studied during four consecutive non-breeding seasons (2014-2018) using systematic counts and resightings of ringed individuals in two shallow bays with known aggregations of other shorebird species. Maximum seasonal abundances (+/- SD) at each bay (68.8 +/- 13.4; 85.0 +/- 13.2) were similar across years. However, actual abundance on Chiloe is probably higher, as other suitable habitats were not surveyed. A total of 55 resightings corresponding to 14 individuals were recorded. The majority (72%) was for birds present during consecutive seasons; there were no recorded interchanges between bays. All birds, but one in Argentina, were ringed on the Atlantic coast of the USA (mainly the Gulf of Mexico) during their spring (northward) migration. Mark-resight data reveal a strong migratory connectivity between the southern Pacific coast of South America and the Atlantic coast of North America for this small but regular population of a highly imperilled species. Data also suggest that the red knots on Chiloe might be considered a separate conservation unit (most likely subspecies rufa). Thus, there is an urgent need to conduct comprehensive studies on Chiloe Island for the conservation of the intraspecific diversity of this migratory flagship species.