Correlates of avifaunal diversity along the elevational gradient of Mardi Himal in Annapurna Conservation Area, Central Nepal

Abstract

Background: Patterns of biological diversity and richness can vary along the elevational gradients among mountain systems making it difficult to conclude the general pattern. The drivers of such pattern are also poorly known in the southern flank of the Himalaya due to limited studies. Therefore, we assessed the species richness, seasonal patterns and drivers of avian diversity along an elevational gradient on Mardi Himal trekking trail, a newly open tourist route in Annapurna Conservation Area of the central Himalaya. Methods: Two surveys (winter and summer seasons of 2019) were conducted from the bank of Seti-Gandaki River confluence (1030 m above sea level, asl) up to the Low Camp (3050 m asl) of the Mardi Himal. The point count method was employed in every 100 m rise in the elevation. Diversity indices were calculated and bird abundance data on species, sites, seasons and environmental variables were analyzed. Generalized linear model, polynomial regression and ordinary least square regression were performed to examine the importance of environmental factors in shaping the avian richness pattern. Results: A total of 673 individuals of birds belonging to 112 species, of which 72 in winter and 80 in summer, were recorded. We observed a hump-shaped pattern of the overall species richness along the elevational gradient. The richness pattern remained consistent even when explored by season, for winter and summer separately. Diversity indices were found higher during the summer. Elevation and mean monthly temperature in both seasons showed non-linear relation with avian species richness. Precipitation exhibited positive association in summer whereas the same in winter was negatively correlated with avian species richness. Distance to the nearest water source and the nearest human settlement were negatively correlated with the richness of birds. Small-ranged and insectivorous birds were under the strong influence of gradients on climatic variables like temperature and precipitation. Conclusions: We conclude that the combined effects of multiple factors such as area, gradients of climate (i.e. temperature and precipitation), resource availability and disturbance play an important role in bird diversity and richness pattern along an elevational gradient of a montane environment in Mardi Himal.

Elevational pattern and seasonality of avian diversity in Kaligandaki River Basin, central Himalaya

“…In general, species richness has been reported to follow one of the four main diversity patterns: decreasing with elevation, low plateau, low plateau with a midelevation peak, and mid-elevation peaks. Of these, 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 2017Chen et al , 2020Pandey et al 2020).…”

“…Of these, 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 2017Chen et al , 2020Pandey 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).…”

Bird community structure as a function of habitat heterogeneity: A case of Mardi Himal, Central Nepal

“…Spatiotemporal distribution of some key environmental resources governs abundance of bird species (McCain 2009). Therefore, studies have attempted to study factors that affect bird abundance and distribution at spatial and temporal scales (He et al 2019;Pandey et al 2020). Studies have shown association of particular bird species to the specific habitat (Brawn et al 2001;Seymour and Simmons 2008).…”

“…Annapurna Conservation Area (ACA) is one of the Important Bird and Biodiversity Areas (IBAs) and a global hotspot of bird diversity (BCN 2011;Pandey et al 2020). It is one of the largest protected areas of Nepal covering an area of 7629 square kilometers.…”

“…Mardi Himal trek is a newly established (officially opened in 2012 AD) trekking trail that lies in the southwestern side of the Annapurna mountain range in the ACA (Pandey et al 2020). To date, research along this route to exhibit the avian species distribution and abundance on different habitat types is lacking.…”