Monitoring of colour banded Red knots (Calidris canutus rufa) that stop over in Penísnula Valdés, Argentine

D'AMICO, VERÓNICA L.; ESCUDERO, GRACIELA; FRIXIONE, MARTÍN

Suecia

Congreso; Wader Study Group 2006 Meeting; 2006

Red knot, Calidris canutus rufa, is a long distance migrant that stopover at Peninsula Valdes’ beaches during northward migration, from Tierra del Fuego to Canadian Arctic. As part of a monitoring program of rufa knot population, we have surveyed beaches and mudflats in the two gulfs of Península Valdés, Patagonia, Argentine; Fracasso (San Jose Gulf) and Colombo (Nuevo Gulf). Information on resights of ringed birds was used to evaluate site fidelity, time length of the stop-over and migratory movements of the species. The area was visited during migrating season in 2004, 2005 and 2006. Using binoculars, scopes and digital photographs we completed total surveys, follow up of the flocks and scans for colour bands. Information of individually marked birds showed that 25 % of the birds seen in 2004 were seen again in 2005, while the 90 % of birds seen in 2005 and the 58.3 % seen in 2004 were seen again in 2006. Three birds with individual colour combinations were observed the three consecutive seasons and five birds were seen in two beaches on the same day. The latter would suggest an integral use of Península Valdés, or even a bigger area, as feeding / stopover site. Each year the same individual marked birds stayed during the complete season, indicating that it would be the same big flock that remains in the area for about a month. Maximum counts were close to constant during April (2000 in 2004, 300 in 2005-only two visits- and 700 in 2006), decreasing markedly at the beginning of May when they may leave to continue migration to the north. On one hand, the results indicate site fidelity for a group of birds, and on the other hand the decrease in numbers of birds through the years may reflect the declining trend observed at the population levels.