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Seasonal patterns of spatial variation in understory bird assemblages across a mosaic of flooded and unflooded Amazonian forests

Beja, Pedro, Santos, Carlos David, Santana, Joana, Pereira, Maria João, Marques, J. Tiago, Queiroz, Hélder Lima, Palmeirim, Jorge M.
Biodiversity and conservation 2010 v.19 no.1 pp. 129-152
Alcedinidae, birds, breeds, feeds, floodplains, floods, forest reserves, forest types, habitats, highlands, landscapes, montane forests, nests, occupations, pollution load, rivers, seasonal variation, understory, Amazonia
We examined seasonal patterns of spatial variation in understory bird assemblages across a mosaic of upland and floodplain forests in central Amazonia, where variation in flooding patterns and floodwater nutrient load shapes a marked spatial heterogeneity in forest structure and composition. Despite great differences in productivity due to flooding by either nutrient-rich “white waters” (várzea) or nutrient-poor “black waters” (igapó), bird assemblages in the two floodplain forest types were relatively similar, showing lower abundances than adjacent upland forests (terra firme) and sharing a set of species that were absent or scarce elsewhere. Species that breed in pensile nests overhanging water were abundant in floodplain forests, whereas species that feed on the ground were generally scarce. Flooding affected assemblage dynamics in floodplain forests, with some influx of ground-dwelling species such as ant-following birds from adjacent upland during the low-water season, and the occupation by riverine and aquatic species such as kingfishers during floods. Spatial configuration influenced the seasonal pattern of assemblage structuring, with movements from terra firme occurring primarily to adjacent igapó forests. No such influx was detected in várzea forests that were farther from terra firme and isolated by wide river channels. Results support the view that habitat heterogeneity created by flooding strongly contributes to maintain diverse vertebrate assemblages in Amazonia forest landscapes, even in the case of largely sedentary species such as understory forest birds. Including both upland and floodplain forests in Amazonia reserves may thus be essential to preserve bird diversity at the landscape scale.