Spatiotemporal Patterns of Bird Vocalizations and Species Richness in the Nanling Mountains Based on Passive Acoustic Monitoring

Passive acoustic monitoring (PAM) provides a novel approach for long-term and continuous monitoring of bird communities, yet its systematic application and ability to capture temporal dynamics in complex montane environments remain limited. From May 2023 to May 2024, eight acoustic recorders were deployed along an elevational gradient (600-1700 m) in the Nanling Mountains, Guangdong, China, to investigate the elevational distribution patterns and temporal rhythms of bird diversity. A total of 88 species from 12 orders and 39 families were recorded. Overall, species richness exhibited a unimodal pattern along the elevational gradient, peaking at 1300 m with 62 species. Functional groups showed distinct elevational responses: resident species displayed a unimodal distribution, whereas summer migrants increased with elevation; passerines were most diverse at mid- to high elevations (1200-1700 m), scansorial birds exhibited a unimodal pattern, and raptors displayed a bimodal distribution; insectivorous and omnivorous species increased significantly with elevation (p<0.05). Temporally, vocal activity and species richness were significantly higher during the day than at night (p<0.001), and higher in the breeding season than in the non-breeding season (p<0.01), with June representing the annual peak in acoustic activity. Both elevation (p=0.003) and month (p<0.001) had significant effects on call abundance and species richness. These results demonstrate that continuous PAM effectively captures the spatiotemporal differentiation of bird diversity in the Nanling Mountains, providing robust technical support for regional bird monitoring and conservation.