Distribution and diversity patterns of birds along the elevation gradient of the Aravalli Hills of Mount Abu Wildlife Sanctuary, Rajasthan, India

Abstract

Study was carried out on the distribution, species richness, diversity and abundance of bird communities along the altitudinal gradient of the Aravalli ranges of Mount Abu Wildlife Sanctuary (MA-WLS). Study area's altitude varies from 280 to 1722 meters above sea level (m.a.s.l.). The study area was categorized into three altitudinal ranges: Range I or lower altitudinal range (B). Range II or middle altitudinal range and (C). Range III or higher altitudinal range. This categorization was done on the basis of vegetation composition and types of forests along altitude, we observed 201 bird species from three altitudinal ranges and habitats in MA-WLS, representing 63 families and 19 orders. Out of these 19 orders of birds, the Passeriformes order was most diverse in terms of species richness with 86 species followed by Charadriiformes (17), Anseriformes (15), Pelecaniformes and Accipitriformes (13 species for each order).  Selected three altitudinal ranges, the most diverse range in terms of bird species richness, individuals and diversity was the altitudinal range I (species = 190; bird individuals = 25888; Simpson diversity index = 0.987; Shannon diversity index = 4.719) followed by range II (species = 152; bird individuals = 17850; Simpson diversity index = 0.983; Shannon diversity index = 4.471) and the lowest species richness and bird individuals were observed in the altitudinal range III (species = 124; bird individuals = 11198; Simpson diversity index = 0.980; Shannon diversity index = 4.327). It was observed that the species richness, diversity and abundance exhibit a monotonic decline pattern along the increase in altitudinal gradient. The relative abundance of each species also differs according to the altitudinal variation. The diverse range of habitats found across the altitudinal gradient in MA-WLS contributes to a high diversity and abundance of bird species. The existence of seasonal and perennial water bodies, as well as variations in floral composition across different altitudes, sustains a variety of aquatic and terrestrial species that reside or migrate in MA-WLS.