Description of a mixed waterbird colony at Laguna Iberá, Corrientes Province, Argentina

Abstract

In the breeding season 1991-1992 a mixed water-bird colony of about 400 nests of Egretta thula, Casmerodius albus, Nycticorax nycticorax, Ardea cocoi and Anhinga anhinga appeared at Laguna Iberá, Corrientes Province, Argentina. It was unique for its type in the area. Observations were carried out during two breeding seasons. The dominant species during the first season was E. thula (52.5% of the nests) followed by C. albus, During the next season the colony expanded in area and in number of nests (87%). The dominant species was now C. albus, with 80,5% of the nests and a growth of 399%. AII the remaining species declined, and N. nycticorax was apparently absent. Evaluation of the impact of human visitors on the colony requires further monitoring.