Influência de fatores bióticos e abióticos na ocorrência e abundância de garças e socós em lagos do Arquipélago de Anavilhanas, Amazônia Central

Abstract

Birds associated with aquatic environments have been studied for many years, especially in the northern hemisphere, and in the last decades also in southern Brazil. However, in the Brazilian Amazon most studies were carried out on systems of muddy water. This present study is the second on birds associated with aquatic environments of black water in the Brazilian Amazon, and the first to investigate the effect of environmental factors, biotic and abiotic, on the occurrence and abundance of five species of herons in 45 lakes. The study was done in the Anavilhanas National Park, during the early flood of 2007. Two regression models were used to evaluate the effects of environmental factors on the occurrence and / or abundance of five species of herons: Ardea alba, Ardea cocoi, Egretta thula, Butorides striata and Tigrisoma lineatum. The first regression model assessed the effects of the depth of the lake, the water transparency, the concentration of nitrogen and phosphorus and the richness of marginal habitats. The second regression model primarily aimed at testing the effects of the lake geographical isolation, and assessing the following variables: the lake form, the distance of the riverbank and the nearest lake. All species of herons except for Ardea cocoi had their occurrence and / or abundance influenced by at least one of the variables. Nonetheless, the general models explained little of the variation in abundance and the occurrence of these species. It probably happened because other factors also influence the distribution and abundance of herons in the Anavilhanas lakes.