Aim: Current diversity patterns in local communities result from historical and contemporary events that operate at distinct spatial and temporal scales. ​However, the contribution of local and large-scale processes in structuring species diversity remain a contentious topic in ecology. We investigated diversity patterns (species richness, composition and number of captures) of understorey bird assemblages in Amazonian unflooded (terra firme) forests. We sought to understand whether understorey bird assemblages in distinct areas of endemism show distinct patterns of diversity, and whether species replacements among areas of endemism occur while the proportion of species within guilds remains stable.

Location: Amazonia.

Taxon: Understorey birds.

Methods: To investigate diversity patterns, we compiled studies that mist-netted birds at 11 regions across seven Amazonian areas of endemism. We used coverage-based rarefaction curves, non-metric multidimensional scaling (NMDS) and created a heatmap based on the proportion of captures in each area of endemism to access patterns of richness, composition and captures of understorey birds, respectively. The relative variance (RVgp index) was calculated to investigate the existence of guild proportionality within each area of endemism.

Results: Bird assemblages diverged across the seven areas of endemism, in terms of species richness, composition and captures. However, the proportion of species and individuals within guilds was similar among areas of endemism, indicating that species replacements across areas of endemism occur while maintaining the same ecological functions. Guild proportionality suggests that interspecific competition and resource availability are more important than environmental heterogeneity in structuring understorey bird assemblages.

Main conclusions: The similar proportion of species within guilds suggest that interspecific competition and resource availability are more important than environmental heterogeneity in structuring local assemblages, possibly via a process of limiting similarity in morphological and functional traits. The observed congruent structure in understorey bird assemblages across areas of endemism shows that coupled historical and ecological processes, operating at local to large scales, have led to current patterns of diversity and composition in Amazonian bird communities.

We compiled data from 11 studies that used mist-nets to sample birds within different areas of endemism across Amazonian terra firme forests. Mist-net studies used here were implemented with distinct designs, goals and contexts (see Appendix S1 in Supporting Information), resulting in large variation in the number of captured individuals per landscape (between 389 and 3,582 captures for long temporal sampling).

We focused on understorey terra firme species and removed species that fit at least one of the following three criteria: i) species that are not typically found in the understorey (i.e. species that preferably inhabit the midstorey and canopy); ii) species that inhabit mainly open-habitat areas (e.g. campinas); and iii) species that inhabit flooded areas but that may occasionally also occur in the understorey of terra firme forest (see Appendix S2 in Supporting Information). Species selection was based on two databases (Stotz et al., 1997; Wilman et al., 2014) that contain information on habitat use and foraging stratum (understorey, midstorey and canopy). The list was subsequently revised by two ornithologists with extensive field experience in Amazonia. We also excluded recaptures from all analyses as we were interested in the number of individuals per species. 

There are 2 different datasets:

1. "Capture data.csv": Capture data of understorey birds, sampled in seven Amazonian areas of endemism. Each line corresponds to a species and the number of individuals captured in each sampling area, with the respective information on food guild and body size, sociability and foraging substratum.

2. "Metadata.csv": Metadata of the items 'sociability' and 'foraging substratum'.