Seasonality and assemblages of non-passeriform waterbirds in várzea lakes on the lower Amazonas River, Santarém, Pará, Brazil

Abstract

Amazonian várzeas are annually flooded for at least five months, which influences the occurence of waterbirds. This study investigates the species richness and composition, and individual abundance of waterbird assemblages in 10 várzea lakes on the lower Amazon River across a seasonal cycle. A total of 7,970 birds belonging to 52 species were recorded. Of these, 25 species were present in all four phases of the cycle, 5 in three phases, 10 in two and 12 during just one phase. Families with the highest species richness were Ardeidae and Scolopacidae. In the dry season, we recorded the highest species richness and the highest total abundance values. Thirteen species showed variation in abundance across the seasonal cycle, most being more abundant in the dry season Variation in species richness, abundance, and composition suggests that research on waterbird assemblages in Amazonian várzeas should consider all phases of the seasonal cycle. Furthermore, the occurrence of several migratory species demonstrates the importance of this region for the conservation of this group. Multi-year monitoring would contribute to a better understanding of the dynamics of Amazonian várzea waterbird assemblages.