USING CANOPY AND UNDERSTORY MIST NETS AND POINT COUNTS TO STUDY BIRD ASSEMBLAGES IN CHACO FORESTS

Abstract

We sampled birds with mist nets and point counts in old-growth and second-growth Chaco forest in Argentina to compare the contribution of each method to estimates of species abundance and diversity. We captured 53 species with mist nets (13 exclusively), and detected 75 species on point counts (43 exclusively). Species richness estimated by rarefaction curves did not differ between methods, except in old-growth understory, where point counts detected fewer species than mist nets. Both methods showed similar patterns of bird diversity and distribution, although point counts revealed more differences between forest layers and forest types. Mist netting contributed to the detection of cryptic or secretive species, especially in the understory, but large-bodied (>200 g) species were detected by point counts alone. Multivariate analysis discerned guilds and species associated with different forest layers and types. Point counts seem to better reflect relative abundance, whereas mist nets may be more sensitive to bird activity (e.g., movements between resources). The simultaneous use of both techniques enhances the description of bird communities, and birds' use of habitats.