Journal of Threatened Taxa | www.threatenedtaxa.org | 26 January 2018 | 10(1): 11185–11191

 

 

 

 

A short-term survey report on the post-winter avian diversity in Corbett National Park and associated areas, Uttarakhand, India

Srinjana Ghosh 1 & Tanmay Bhattacharya 2

1 Department of Zoology, Bethune College, 181, Bidhan Sarani, Manicktala, Azad Hind Bag, Kolkata, West Bengal 700006, India

2 Professor and formerly Head of the Department of Zoology, Vidyasagar University, Midnapore, West Bengal 721102, India

1 srinjanaghosh15@gmail.com (corresponding author), 2 tanmaybhattacharya@yahoo.com

 

 

 

 

 

Abstract: This study documents a short-term post-winter survey of avifaunal diversity in Corbett National Park and associated areas in Uttarakhand. Qualitative and quantitative avian diversity patterns were assessed from a biomonitoring and conservation perspective. A total of 94 species of birds belonging to 40 families under 15 orders were reported. Among these 10 were winter visitors, six summer visitors and one near-threatened species. Habitat distribution and foraging guild patterns are discussed. Insectivores and nectarivores were found to be the prominent foragers. Open woodland, cultivated land and forest edges provided shelter for many bird populations, while plantation areas supported the lowest numbers of species. The study area was exposed to varying levels of anthropogenic interventions, yet supported a healthy bird diversity with low dominance index.

Keywords: Anthropogenic intervention, avifaunal diversity, biomonitoring, dominance index, foraging guilds, habitat distribution, summer visitor, winter visitor.

 

INTRODUCTION

The Himalaya are a significant avian biodiversity hotspot, harbouring 977 endemic species of birds, of which eight are threatened and deserve special conservation priority (Karmakar et al. 2010). Western Himalaya is an important area for bird diversity, and it has been designated as Endemic Bird Area 28 (Corbett Tiger Reserve Bird Checklist 2001). The unique topography, climate, soil texture and vegetation patterns support diverse ecosystems, habitats, communities and species. The Corbett National Park (CNP), contains a mosaic of broad leaf mixed, dry deciduous, moist deciduous and conifer forests, and is a refuge for 549 species of birds (Corbett Tiger Reserve Bird Checklist 2001; Badola et al. 2010; Kidwai et al. 2013). Like many other parts of the country CNP is also suffering from habitat modification and resource alteration. The objectives of the present study are to prepare an inventory of avian diversity, including quantitative and qualitative assessments of community patterns in relation to existing habitat heterogeneity and foraging guilds, based on conventional niche dimensions like common foraging habitats and foraging components. Relative abundance values of the observed bird species were estimated to obtain an overall picture of community composition in the concerned regions.

MATERIALS AND METHODS

Study Site

Corbett National Park (CNP) is located in the foothills of western Himalaya in the districts of Nainital and Pauri Garhwal in the hill state of Uttarakhand, India (29.53000N & 78.77470E). A varied landscape of mosaic habitats prevails, consisting of wet and dry, plain and mountain, gentle and rugged, forests and grasslands crisscrossed by rivers, streams, ridges and wetlands fed by the Ramganga River and its tributaries prevails. Vegetation comprises of three broad categories: northern tropical moist deciduous, northern tropical dry deciduous, subtropical pine forest/shiwalik-chir-pine forest. A mosaic of dry and moist deciduous forest, scrub savannah and alluvial grassland is prominent. The most dominant and widely distributed species is Shorea robusta, followed by Mallotus philippensis and Syzygium cumini. Temperature ranges between 40C in winter and 420C in summer on average. Average annual rainfall ranges between 1,500-1,600 mm, most falling during the monsoon (June to September). Little rain may occur in winter. The study was conducted in the last week of March 2015, representing a post-winter season with average temperature range of 6–12 0C.

Based on available literature and information collected from local forest management personnel, six representative sampling sites were selected, including open grassland, open woodland, forest edges, cultivated patches in buffer zones, dense vegetation with canopy coverage (dense forest) and sites related to water bodies. Each site was visited thrice a day between 07:00­–09:00 hr, 11:00–13:00 hr and 15:00–17:00 hr, consecutively for four days. Time frames were selected to optimize observation of bird foraging and nesting in early morning and late afternoon, and resting during early afternoon. Bird census was conducted by following transects, point counts and territory mapping (Bibby et al. 1998). Point counts were used to estimate populations when the topography of the area was not ‘open’, involving a series of points or stations at which birds were counted (Gregory et al. 2004). Line transect methods were also applied wherever possible (Bibby et al. 1998).

All birds (sitting, perching, foraging, swimming and flying) were recorded and identified in their natural habitat and distribution areas following existing literature (Ali & Ripley 1983; Bibby et al. 1998; Kazmierczak & Perlo 2000; Grimmett et al. 2011; Praveen et al. 2016), either directly in the field, or from photographs. The assistance of well-trained guides was also relied upon.

Dominance index was calculated following McNaughton & Wolf’s (1970) equation: DI=100 (Y1+Y2)/Y; where Y1, and Y2 are the number of individuals of the two most common species and Y is the total number of individuals belonging to all the species.

 

 

RESULTS AND DISCUSSION

This study documented 94 species (Table: 1) from CNP and nearby regions. Passeriformes was the dominant order comprising 19 families and 43 genera. Table 1 and Fig: 1 reveals that the orders Anseriformes, Cuculiformes, Gruiformes and Strigiformes were represented by single family and single genus each. Seventeen families viz., Anatidae, Cuculidae, Rallidae, Scolopacidae, Strigidae, Upupidae, Picidae, Coracidae, Campephagidae, Vangidae, Aegithinidae, Rhiphiduridae, Laniidae, Motacillidae, Alaudidae, Sylvidae, Certhidae were represented by single species. Three families Columbidae, Accipitridae and Muscicapidae each had maximum number of species (6). Only one species (Vanellus duvaucelii) (Table 1) belonged to Near Threatened (NT) in IUCN Red List of Threatened Species category (IUCN 2014). Most of the species (78) encountered were residents and six species were strict winter visitors. Four winter visiting species viz. Streptopelia orientalis, Charadrius dubius, Accipiter nisus and Alauda gula gula sometimes were reported to stay yearlong in the CNP landscape. Likewise five summer visitors were also reported to stay back viz. Upupa epops, Merops orientalis, Hirundo rustica, Ficedula tricolor, Ficedula superciliaris. There was only one species of strict summer visitor viz., Eumyias thalassinus (Grimmet et al. 2011).

Table 1 also reveals that there were 11 common species with relative abundance exceeding 2.5%. Psittacula cyanocephala and Pycnonotus cafer were the most common species with relative abundance of 4.36% followed by Dicrurus macrocercus (3.63%), Turdoides striata (3.28%), Acridotheres tristis (3.28%), Psittacula eupatria (3.28%), Bubulcus ibis (3.38%), Streptopelia chinensis (2.99%) and Merops orientalis (2.79%), Egretta garzetta and Acidotheres ginginianus (2.65%) in that order. Dominance index (DI) was calculated to be 8.72. Such a low DI is indicative of the homogeneity of the bird community and reflects a relatively stress-free and equitable environment prevailing in CNP. McNaughton & Wolf (1970) showed that the DI increases with the harshness and decreases with the equitability of the environment. Karr (1971) opined that DI for avifauna declined with the vegetation development. Changes in vegetation compositions along geographical and environmental gradients also influence varying trends of relative abundance of bird species (Lee & Rotenberry 2005).

Forest and edge offer habitats for diverse avian guilds. Increased floral structural complexity and floristic composition are often associated with enriched avian communities (Laislo 2002). As documented in Fig. 2, maximum number of species were supported by open woodland (21%) followed by the forest edge, grassland and cultivated land (15%). Wetlands also supported a considerable proportion (12%) but plantation areas despite their huge vegetation shelter being monoculture only nurture limited number (8%) of birds.

Same species may be represented with different observable densities in different forest types, reflecting microhabitat preferences and resource availability. Such differential distribution patterns were qualitatively documented for species like Dicrurus hottentottus, Turdoides striata, Pycnonotus sp., Psittacula sp. etc.in the present study. As they are becoming more specialized feeder rather than a generalised one depending on a particular vegetation type as food resource. The forest with most stable fixed pattern (e.g., Sal forests) entertained more specialist species. As documented in Fig. 2, the highest number (35) of visitor species frequent the mid canopy layer, followed by upper canopy and lower bush levels (30). Understorey, upper bush level and lower canopy also held moderate number of birds whereas wetlands like mud patches, stream banks were preferred by a specific and limited number of species which found that particular habitat suitable. Fifty-seven solitary, 40 pairs and 13 parties were observed in the present study. Often interspecific associations comprising of habitat specific ecological guilds were seen. The dietary guilds as observed are shown in Fig. 3. Carnivores (59%) top the list, followed by herbivores (31%), omnivores (7%) and scavengers (3%) in that order. Among carnivores, insectivores were the most dominant group comprising 60%. Among herbivores, no feeding guild was conspicuously dominant. Frugivores comprised 36%, nectarivores (33%) and graminivore (24%). Variation in foraging structure was caused by several factors like predation risk, physical framework of the habitat and microclimatic constraints (Cueto & Casenave 2002). Members of the same guild exploit the similar resources and become susceptible to potential competition over shared resources and in order to co-exist they would adopt mechanisms to reduce but not necessarily eliminate negative competitive interactions (Simberloff & Dayan 1991; Palmer et al. 2003). Herein lies the importance of conserving species-specific habitat patches.

Another interesting finding was related to the appearance of wetland avifaunal distribution encompassing both semiaquatic (river bank, river beds, dam) and aquatic (short stream, pools, wetlands, watery scrubs, water logged marshlands) habitat patches dispersed within the forest stretches. Wetlands played the role of typical indicator of the health of the overall forest ecosystem as 20% of threatened bird species in India inhabit wetlands (IDFC 2002). Wetlands provide a favourable place for roosting and thermoregulation for some birds like Mycteria leucocephala. Potential threats to these wetland communities includes the agricultural runoffs, urban-industrial expansions; and dam constructions. Community based conservation measures should be taken to save these forest wetlands (Kingsford 2000). Of 33 species of wetland birds, documented herein, six were winter visitors and only one was a summer visitor.

In the present study, a total of 94 species belonging to 15 orders and 40 families were reported from different forest habitats, including terrestrial, aquatic and semi-aquatic stretches. The low Dominance Index revealed an overall healthy ecosystem. It is now the responsibility of administrative authorities and policy makers to maintain this important hub for avian species.

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