Balbina Understory Bird Data from 2023 to 2024

This study was conducted in the Balbina Hydroelectric Reservoir and adjacent areas of continuous forest, located in the northern region of the State of Amazonas, Brazil (1°40′53″S, 59°39′09″W). We selected 37 sample sites, five in continuous forest sites and 32 in forest islands. Fieldwork was carried out from June to December 2023 and June to November 2024. At each sample site, we surveyed birds using 16 mist nets (12 x 2.5 m, 32 mm mesh, Ecotone 1016/12) set in the understory along a continuous near-linear ca 200-m net-line whenever possible. On islands smaller than 4 ha (n = 6), we installed mist nets in a cross-shaped arrangement to ensure a standardised sampling effort. Each net line was placed at a minimum distance of 2 km from the others (mean ± SD = 27.87 ± 15.39 km; range = 2.04 – 68.56 km). Nets remained open from 06:00h to 15:00h for two days each year, resulting in a sampling effort of 576 net-hours per sampling unit and a total of 21,312 net-hours (16 nets × 9 hours × 2 days × 2 years × 37 sampling units). Birds were identified following the nomenclature of the Comitê Brasileiro de Registros Ornitológicos (Pacheco et al., 2021), and marked individually with number-coded metal rings provided by the Centro Nacional de Pesquisa e Conservação de Aves Silvestres (CEMAVE) to track recaptures. The study was conducted under authorization from the Sistema de Autorização e Informação em Biodiversidade (SISBIO, permit 87488) and the CEMAVE (permit 4836).Pacheco JF et al. 2021 Annotated checklist of the birds of Brazil by the Brazilian Ornithological Records Committee—second edition. Ornithol. Res. 29, 94–105. (doi:10.1007/s43388-021-00058-x)