Seasonal Variation and Vertical Distribution of Bird Diversity in Wenshan, Yunnan Province

Wenshan City, located in southeast of Yunnan Province, is a part of the Xishuangbanna Biodiversity Conservation Priority Area and is home to a wide range of biological species. Bozhushan is situated in the Laojunshan Area of the Wenshan National Nature Reserve and is known as the "Highest Peak in Southern Yunnan". It is an ideal place to study biodiversity patterns along elevational gradients. In this study, we aimed to study the differences in bird diversities inside and outside the Nature Reserve (Laojunshan Area) and along the elevational gradient in the Laojunshan Area. Bird surveys were conducted in breeding and non-breeding seasons in Wenshan City from July 2019 to April 2020. To do this, a total of 18 transects were placed along 5 elevational bands with an interval of 300 m inside the nature reserve, and other 41 transects were placed outside the nature reserve in 10 km×10 km grids. A total of 199 bird species (from 51 families of 16 orders) were found, with 24 of which are China's national key protected bird species. Of these, 147 species (from 47 families of 16 orders) were found outside the reserve, and 149 species (from 45 families of 12 orders) were found inside the reserve. In the breeding seasons, the Pielou index of bird communities within the reserve was significantly higher than that of outside the reserve (P=0.028, Z=-2.191). In the non-breeding season, the number of species outside the reserve (P=0.002, Z=-3.165) and the Shannon-Wiener diversity index (P=0.005, Z=-2.776) was significantly higher than that within the reserve. The non-metric multidimensional scaling method (NMDS) and permutational multivariate analysis of variance (PerMANOVA) showed significant differences among bird communities inside and outside the reserve. The peaks of bird species richness in the reserve (Laojunshan Area) are found in the elevation band of 1 700-2 000 m in both breeding season and non-breeding seasons. Meanwhile, many bird species significantly shifted their elevational ranges downslope from breeding to non-breeding seasons. The area of the reserve only accounts for 7.71% of Wenshan, while the bird richness accounts for 74.87% of Wenshan, underscoring the important role in the maintenance of regional bird species of the nature reserve. To protect the regional bird diversity, maintaining the forests in the nature reserve, particularly the middle elevations (i. e., 1 700-2 000 m), is the key issue. Attention should also be paid to the protection of birds and other protected species in the wetlands outside the nature reserve.