Altitudinal and seasonal dynamics of bird diversity in the southern foothills of the Daba Mountains, China

The Daba Mountains is a critical ecological barrier in central China, with diverse landforms supporting rich avian communities. To clarify the species composition, seasonal dynamics, and vertical distribution of birds in its southern foothills — key for biodiversity conservation — we conducted systematic surveys via line-transect and direct observation methods in June (summer) and September (autumn) 2024, covering multiple habitats and altitude gradients. A total of 72 bird species (8 orders, 31 families) were recorded, including 51 residents (70.83%), 13 summer migrants (18.06%), six winter migrants (8.33%), and two passage migrants (2.78%). Zoogeographically, Oriental realm species dominated (37 species, 51.39%), followed by cosmopolitan species (23 species, 31.94%) and Palaearctic realm species (12 species, 16.67%). Summer avian diversity was significantly higher than autumn (P < 0.05), linked to breeding activities and summer migrants. Across the studied altitudinal range, aquatic habitats consistently showed the highest diversity index, whereas farmland and urban-rural habitats displayed the greatest similarity in community composition. Analysis along the altitudinal gradient revealed that the overall species richness showed a mid-peak pattern, peaking at 800–1100 m, Linear Mixed Model (LMM) analysis further confirmed that elevation had a significant effect on bird diversity, with the 800–1100 m band showing significantly higher Shannon-Wiener index values than lower elevations (P = 0.035), while no significant interaction was found between elevation and habitat type. Resident birds exhibited seasonal altitude range expansions. Our study provides baseline avian biodiversity data for the region, enhancing understanding of avian ecological adaptation in mountain ecosystems. This information is valuable for guiding targeted conservation and ecological management in the southern Daba Mountains.