Assembleias de aves noturnas em florestas naturais e plantadas na ecorregião da Floresta de Araucária

Abstract

Nocturnal birds, although widely distributed, remain poorly understood and exhibit sensitivity to environmental changes, being influenced by factors such as habitat structure and circadian rhythms, which regulate their activity patterns, vocalizations, and reproduction. However, their study is challenging due to low detectability, with most records obtained through their vocal behavior. Passive acoustic monitoring (PAM) has proven to be an effective tool to overcome this limitation, enabling aural species identification. In this study, we used PAM to investigate the distribution and vocal activity patterns of nocturnal birds in the Floresta Nacional de Passo Fundo, Rio Grande do Sul, Brazil. In February 2024, autonomous audio recorders were deployed at 18 sampling units distributed across remnants of natural forest and plantations of Araucaria angustifolia and Pinus elliottii, resulting in approximately 3,000 hours of recordings. We identified seven species across three orders and four families, including a new record for the area (Glaucidium brasilianum). Strix hylophila, Lurocalis semitorquatus and Asio stygius were the most frequently detected species, each exhibiting distinct vocal activity patterns: S. hylophila vocalized throughout the night, L. semitorquatus was more active at dusk, and A. stygius concentrated its vocalizations between 20:00 and 00:00. The number of records of S. hylophila and L. semitorquatus did not differ significantly among the habitat types studied, while A. stygius was recorded only at a single sampling unit located in a plantation of Pinus elliottii. This study demonstrated the effectiveness of passive acoustic monitoring in detecting nocturnal bird species, identifying patterns of distribution and vocal activity, and thus filling gaps in knowledge about the local nocturnal avifauna.