Atividade vocal, riqueza de espécies, e os coros e "nãocoros" das aves em dois pontos com condições ambientais diferentes no RN

Abstract

Birds’ vocal activity is a defining feature of this group, and their vocal output is often used as a detection tool (in terms of presence/absence) in many ecological studies about these animals. Birds’ acoustic activity can be influenced by environmental factors that also affect species richness at a given spot. Using audio recordings acquired through Passive Acoustic Monitoring (PAM), this study aimed to i) investigate the influence of a set of environmental factors on birds’ vocal activity (measured as the number of vocalizations) and species richness in two sampling sites with distinct environmental conditions located at Rio Grande do Norte state, Brazil; and ii) compare the influence of the environmental variables on the vocal activity and species richness between the two sites. The study was conducted in the rural zone of the municipality of Currais Novos (Caatinga biome) and at the Parque das Dunas state park, in Natal, during twelve monthly 3-day sampling campaigns, covering two periods (04:00 – 10:00 and 14:00 – 20:00) recording for 1 minute at every 10-minute cycle. Generalized Additive Models (GAMs) were built to evaluate the relationship between six environmental variables, including hourly precipitation, NDVI vegetation index, cloud cover, thermal sensation, light condition and wind speed, and the response variables (vocal activity and species richness). Results suggest that the set of environmental factors play a collective and significant role in this system, with distinct effects of these factors on the response variables in both sampling sites. The factor representing light condition showed the highest estimate values in all models with consistent positive effects. As far as we know, this is the first study to evaluate how environmental factors may influence birds’ acoustic behavior in Brazil, conducted in traditionally understudied environments.