Migratory connectivity and local site fidelity in red knots on the southern Pacific coast of South America

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 Chiloé Island (43°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 Chiloé 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 Chiloé might be considered a separate conservation unit (most likely subspecies rufa). Thus, there is an urgent need to conduct comprehensive studies on Chiloé Island for the conservation of the intraspecific diversity of this migratory flagship species.

Insights into migratory connectivity and conservation concerns of Red Knots Calidris canutus in the austral Pacific coast of the Americas

“…Resightings in Chiloé of birds ringed in the Gulf of Mexico (Texas and Louisiana, USA) support strong migratory connectivity between both areas (Navedo and Gutiérrez 2019). One additional resighting in Chiloé of a knot ringed in South Carolina and another ringed in Argentina (Navedo and Gutiérrez 2019), along with resightings of knots banded in Delaware, and one of two knots banded on Chiloé and resighted in Georgia, respectively (J. Johnson unpubl. data in Andres et al .…”

“…2013). By contrast, at least two knots spending the non-breeding season at Chiloé were resighted in the eastern North Atlantic Coasts during northward migration, one in South Carolina (Navedo and Gutiérrez 2019) and another in Georgia (Johnson et al . 2007), and two birds from Delaware Bay were also resighted in Chiloé (Johnson et al .…”

“…An additional regular non-breeding area was recently reported in Chiloé Archipelago (42°S, Chile) (Navedo and Gutiérrez 2019), a Site of Hemispheric Importance for the conservation of migratory shorebirds (Humedales Orientales de Chiloé; WHSRN 2011) due to its large numbers of Hudsonian Godwit Limosa haemastica and Whimbrel Numenius phaeopus (Andres et al . 2009).…”

“…At least c . 150 Red Knots regularly occupy two studied bays of the main island, one in the north and the other in the central-east coast, showing very high local site fidelity, both intra- and inter- seasonally (Navedo and Gutiérrez 2019). Resightings in Chiloé of birds ringed in the Gulf of Mexico (Texas and Louisiana, USA) support strong migratory connectivity between both areas (Navedo and Gutiérrez 2019).…”

“…150 Red Knots regularly occupy two studied bays of the main island, one in the north and the other in the central-east coast, showing very high local site fidelity, both intra- and inter- seasonally (Navedo and Gutiérrez 2019). Resightings in Chiloé of birds ringed in the Gulf of Mexico (Texas and Louisiana, USA) support strong migratory connectivity between both areas (Navedo and Gutiérrez 2019). One additional resighting in Chiloé of a knot ringed in South Carolina and another ringed in Argentina (Navedo and Gutiérrez 2019), along with resightings of knots banded in Delaware, and one of two knots banded on Chiloé and resighted in Georgia, respectively (J. Johnson unpubl.…”