Abstract
This study explored bird diversity, seasonal variation, and associated factors along an elevational gradient in an important biodiversity area (IBA) of central Nepal: the Kaligandaki River basin of Annapurna Conservation Area. The field survey was carried out in 2019 over two seasons, winter (January and February) and summer (May and June) using the point count method. A total of 90 sampling plots were set up from elevations of 800m (Beni) to 3,800m (Muktinath). Data for variables including the number of fruiting trees (indicator of resource availability) and distance to the road (indicator of disturbance) were collected, and their influence on avian diversity were assessed. The results revealed a diverse assemblage of avian fauna in the study area with consistent species richness over the two seasons. A decline in species richness and diversity with increasing elevation was observed. Of the different habitat types within the study area, forest and shrubland habitats showed the strongest association with bird species distribution and richness. We emphasize the need for long-term monitoring programs with standardized sampling approaches to better understand the avifauna in the central Himalaya.
Highlights
Patterns in the diversity and composition of species along elevation gradients are key issues in ecology (Lomolino 2001) that contribute to understanding global biodiversity (McCain 2009)
Bird diversity in Kaligandaki River basin This study recorded a highly diverse avian fauna dominated by Passeriformes in the Kaligandaki River basin
The high species richness might be attributed to habitat complexity/heterogeneity (MacArthur 1964; Pan et al 2016; Hu et al 2018) along an elevation gradient of the Kaligandaki River basin, comprising riverine Alnus nepalensis forest, Schima wallichi forest, mixed-forest with Tooni ciliata and Bombyx ceiba, Pinus roxburghii forest, Pinus wallichiana forest, Betula utilis forest including agricultural land, human settlement area, shrubberies, grassland and scrublands
Summary
Patterns in the diversity and composition of species along elevation gradients are key issues in ecology (Lomolino 2001) that contribute to understanding global biodiversity (McCain 2009). Midelevation peaks are the mostly observed patterns among vertebrates (Colwell & Lees 2000; Bertuzzo et al 2016; Chen et al 2017; Pandey et al 2020) These patterns can be explained by drivers that can be both spatial (area, mid domain effect) and environmental (temperature, precipitation, productivity, and habitat heterogeneity) (Colwell et al 2004; Wu et al 2013; Chen et al 2017, 2020; Pandey et al 2020). Numerous hypotheses have been proposed to explain relationships between species richness and altitude, such as species-area relationships, mid-domain effects, climate-richness relationships, and productivity-richness relationships (Rahbek 1995; Grytnes & Vetaas 2002)
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