title: Environmental characteristics drive variation in Amazonian understorey bird assemblages.
abstract: Tropical bird assemblages display patterns of high alpha and beta diversity and, as tropical birds exhibit strong habitat specificity, their spatial distributions are generally assumed to be driven primarily by environmental heterogeneity and interspecific interactions. However, spatial distributions of some Amazonian forest birds are also often restricted by large rivers and other large-scale topographic features, suggesting that dispersal limitation may also play a role in driving species' turnover. In this study, we evaluated the effects of environmental characteristics, topographic and spatial variables on variation in local assemblage structure and diversity of birds in an old-growth forest in central Amazonia. Birds were mist-netted in 72 plots distributed systematically across a 10,000 ha reserve in each of three years. Alpha diversity remained stable through time, but species composition changed. Spatial variation in bird-assemblage structure was significantly related to environmental and topographic variables but not strongly related to spatial variables. At a broad scale, we found bird assemblages to be significantly distinct between two watersheds that are divided by a central ridgeline. We did not detect an effect of the ridgeline per se in driving these patterns, indicating that most birds are able to fly across it, and that differences in assemblage structure between watersheds may be due to unmeasured environmental variables or unique combinations of measured variables. Our study indicates that complex geography and landscape features can act together with environmental variables to drive changes in the diversity and composition of tropical bird assemblages at local scales, but highlights that we still know very little about what makes different parts of tropical forest suitable for different species.
authors.affiliation: UFZ - Helmholtz Centre for Environmental Research, Department of Conservation Biology, Leipzig, Saxony, Germany.|Faculty of Biosciences, Pharmacy and Psychology, University of Leipzig, Leipzig, Saxony, Germany.|Coordenação de Pesquisa em Biodiversidade, Instituto Nacional de Pesquisas da Amazônia - INPA, Manaus, Amazonas, Brazil.
authors.forename: Juliana
authors.identifier: http://orcid.org/0000-0002-6968-8275
authors.initials: J
authors.lastname: Menger
authors.affiliation: Coordenação de Pesquisa em Biodiversidade, Instituto Nacional de Pesquisas da Amazônia - INPA, Manaus, Amazonas, Brazil.
authors.forename: William E
authors.initials: WE
authors.lastname: Magnusson
authors.affiliation: New Zealand Institute for Advanced Study - NZIAS, Albany Campus, Massey University, Auckland, New Zealand.
authors.forename: Marti J
authors.initials: MJ
authors.lastname: Anderson
authors.affiliation: Faculty of Biosciences, Pharmacy and Psychology, University of Leipzig, Leipzig, Saxony, Germany.|German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Saxony, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Schlegel
authors.affiliation: UFZ - Helmholtz Centre for Environmental Research, Department of Conservation Biology, Leipzig, Saxony, Germany.|German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Saxony, Germany.
authors.forename: Guy
authors.initials: G
authors.lastname: Pe'er
authors.affiliation: UFZ - Helmholtz Centre for Environmental Research, Department of Conservation Biology, Leipzig, Saxony, Germany.|German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Saxony, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Henle
mesh_terms: D000818:Animals; D044822:Biodiversity; D001717:Birds; D001938:Brazil; D017753:Ecosystem; D065928:Forests; D011157:Population Dynamics; D013045:Species Specificity