Diversity Of Birds Along An Elevation Gradient And Seasonal Variation In Kaligandaki River Basin, Western Nepal

Abstract

Demonstrating the patterns and the underlying mechanism of diversity along elevational gradient has been a powerful test system for understanding and studying biodiversity including the avian fauna. This study aimed to explore the bird diversity, seasonal variation and associated factors along elevation gradient in Kaligandaki River basin in two districts, Myagdi and Mustang of Annapurna Conservation Area. Field survey was carried out in two seasons, winter (Jan and Feb, 2019) and summer (May and June, 2019). Point count method was used for bird survey within three circular plots (radius=30m) in each 100m rise in elevation. A total of 90 sampling plots were set up from elevation of 800m (Beni) to 3800m (Muktinath) within the study area. Data on variables like number of fruiting trees as a proxy of resource availability, distance to road as a proxy of disturbance, and habitat types were collected, and influence was assessed. All the data were analyzed by using Microsoft excel 2016, R software and CANOCO 4.5. Shannon diversity index (H’=4.134) and the evenness index (e= 0.5205) indicated the diverse assemblage of the avian fauna in the study area, whereas one -way ANOVA (Fstat= 0.48, p>0.05) revealed no significant variation in species richness in two seasons within the study period. Monotonic decline in species richness along elevation was illustrated as a pattern of diversity. GLM illustrated that both the species richness and species diversity were negatively associated with elevation. Similarly, distance to road as a predictor variable of disturbance showed reverse association with species richness. However, number of trees analyzed as a variable for resource availability showed positive relationship with species richness and diversity, that means, higher the number of trees, higher the observed avian richness. Likewise, Canonical Correspondence analysis (Monte Carlo significance test with 499 permutations) showed that among different habitat types the species distribution and richness was strongly associated with forest and shrubland habitat. The diverse avian fauna within the study area and their association with different factors needs furthermore detailed and extensive survey to explore more species and other patterns and processes along the elevational gradient.