Annual occurrence of Red Knot Calidris canutus rufa at Punta Rasa, Samborombón Bay, Argentina, over a 30-year period (1985?2014)

MARTÍNEZ CURCI N.S.; BREMER, E; AZPIROZ AB; BATTAGLIA, G; SALERNO, JC; ISACCH JP; GONZALEZ P; CASTRESANA, G; ROJAS, P

Wader Study

International Wader Study Group

Año: 2015 vol. 122

0260-3799

From 1985 to 2014, we monitored numbers of Red Knots Calidris canutusof the subspeciesrufa occurring at Punta Rasa, Samborombón Bay, BuenosAires province, Argentina during northward migration (March to April),and in the austral winter (mid-May to mid-August), when some knots,mainly immatures, remain in South America during the breeding season.Numbers occurring during northward migration declined over the monitoringperiod from a peak of 3,640 in 1987 to 168 in 2014. Thisis consistentwith the concurrent decline of the main Tierra del Fuego wintering population(though the percentage of the Tierra del Fuego population stoppingat Punta Rasa also declined from 5.4% to 1.3%).Numbers occurring at Punta Rasa during the austral winter have alsodeclined, but not to the same extent and for the past decade more havebeen counted during the austral winter than during northward migration.Among those seen at Punta Rasa during the Arctic breeding season havebeen some with large amounts of rufous breeding plumage. The percentageof such birds has increased from 10?15% in 1987 to 19?54% during2011?2014. Moreover, observations of individually marked birdsshow thatsome of those showing breeding plumage are mature adults, at least 3?7years old.Conservation actions are required to manage Punta Rasa for the small butimportant numbers of Red Knots that occur there. Further research isneeded to determine why some mature adults do not go to their Arcticbreeding grounds and thereby fail to contribute to reproduction.