An appraisal of avian species diversity in and around Purulia Town , West Bengal , India

Purulia, the westernmost district of West Bengal, India is least explored with respect to the biological diversity and relatively little information is available to date. The present study was conducted from February 2017 to January 2018 to document avifaunal diversity in Purulia Town and surroundings. Sampling was done through the line transect method with photographic documentation and subsequent identification following suitable keys. Species richness and seasonal abundance were calculated. Altogether, 115 species of birds belonging to 19 orders and 43 families were recorded during the study period. Passeriformes was the most dominant order represented by 46 species during the study. The Shannon-Wiener (H’) value was highest for January (1.564). A large number of migratory birds visit Purulia every year mostly during winter and it is reflected in the present study. Diverse foraging habit among the birds was observed during the study period and omnivorous birds (29%) were found in highest number followed by invertivores (26%), carnivores (25%), granivores (8%), herbivores (7%), frugivores (3%), and nectarivores (2%). The present study is a preliminary effort to document the avifaunal diversity of Purulia and a more extensive systematic study should be carried out to investigate and protect the avifaunal diversity of this region.


INTRODUCTION
About 10,721 species of birds are living in this planet (Billerman et al. 2020) distributed from the polar regions to the tropical forests and are even prominent in the highly populated metropolitan cities. Approximately, 75% and 45% of total bird species around the globe are adapted to forest habitats and human-modified habitats, respectively (BirdLife International 2018), where they play important role in pollination, seed dispersal, pest control, and act as an indicator of a healthy environment (Hadley et al. 2012;Ramachandra 2013). Birds play a crucial role in plant pollination; through their faeces, they carry seeds and initialize the distribution of plants to distant places; act as scavengers, which help in ecological decomposition. Birds are considered good ecological indicators as they exploit all trophic levels in a food chain acting as herbivore, carnivore, or omnivore. They respond to the qualitative and/or quantitative changes in the environment and usually indicate the secondary changes in their surroundings (Morrison 1986;Koskimies 1989). Population dynamics of bird species may indicate natural disasters like drought (Blake et al. 1994) or anthropogenic stress like the introduction of new species in the ecosystem and urbanization (Savidge 1984;O'Connell et al. 2000).
Habitat loss is one of the key factors responsible for the rapid decline of the avian species population (Prasad et al. 2014). Anthropogenic activities like agriculture, urbanization, and firewood collection have contributed to deforestation and the simultaneous habitat degradation of the bird communities that affect the variety and variability of bird population (Storch et al. 2003). Understanding the changes in the diversity and abundance of the birds linked with the degradation of the natural habitats and ecosystems could help in framing necessary conservation actions.
Avian species diversity and distribution are not consistent with the landscape (Bibby et al. 1992). The pattern of biodiversity changes with environmental factors, climatic conditions, topography and habitats (Rodríguez-Estrella 2007;Jankowiski et al. 2009 (Das 2016;Samanta et al. 2017). Purulia has been least explored concerning the biological diversity and relatively little published information is available to date (Das 2016;Samanta et al. 2017;Das 2018). In this circumstance, to enrich the knowledge on the biodiversity profile, an attempt was made to update the information about birds of Purulia Town and surroundings for the diversity and seasonal abundance. The main objective of the study was to determine bird species diversity and abundance to prepare a checklist of birds as well as to create awareness among the local people of Purulia to help maintain the ecological balance.

Study Site
The present study was carried out to document the avifaunal diversity from February 2017 to January 2018 in and around Purulia Town (23.33 N;86.36 E), Purulia, West Bengal, India. Five locations, namely, Ketika, Sidho-Kanho-Birsha University campus, Saheb Bandh, Surulia Deer Park, and Kansai river-side, situated in and around the town were selected for the study (Fig. 1). Ketika, situated about 2km from Purulia railway station, is a well-wooded residential area with trees, bushes, open lands with intermittent small ponds, and ditches. Sidho-Kanho-Birsha University campus is a vast open land with scattered bushes and trees. Saheb Bandh is a large manmade lake with some vegetation surrounding it. Surulia Deer Park is an urban forest with a mini zoo inside it. Kansai river-side was the area around the bank of river Kansai flowing by the south boundary of the town.

Data collection
Each study site was visited once a month. Line transect method was employed to record avifaunal richness and abundance (Hutto et al. 1986;Bibby et al. 1992;Buckland et al. 2004). The field surveys were conducted at 06.30-07.30 h, 12.00-13.00 h, and 16.30-17.30 h, and the values were averaged to obtain representative data of a particular count (Gibbons & Gregory 2006).
From the starting spot of any predetermined route, the bird species or their calls were recorded along either side of the transect. The starting point and the direction of transects were often random. The length of the route often varied due to topography, roads, water body that limited access. The opportunistic counts of birds during other times and other places were also included to J TT document a comprehensive checklist (Hossain & Aditya 2016).
Following visual observation or hearing a bird's call the presence of the birds was confirmed with the help of a binocular (Olympus 8 × 40 DPS1) and photographs were taken with digital cameras (Nikon Coolpix P520 and Canon 1200d, 55-250mm lens). Based on the visual observations and photographs, birds were identified following standard guidebooks (Ali 2002;Grimmett et al. 2011). Monthly data obtained from the one-year study was divided into four seasons: summer (March to May), monsoon (June to August), post-monsoon (September to November), and winter (December to February) to compare seasonal variations in avian species richness and abundance.
Species richness and diversity were calculated using Biodiversity Pro software (McAleece et al. 1997). The bird species diversity was calculated using the Shannon-Wiener diversity index [H′ = ∑ p i lnp i ] and Shannon diversity index [H max = Log 10 (S)]. Measurement of Shannon's evenness index was calculated using the following formula J = H′/ H max (p i = proportion of total sample belonging to i th species, S = total number of species in habitats (species richness) (Magurran 2004).
Migratory status and feeding habits of the enlisted birds was determined by personal observation as well as information available in the literature (Ali 2002;Grimmett et al. 2011;Birdlife International 2018).

RESULTS
In the present study, 115 species of birds consisting of 19 orders and 43 families were recorded in and around Purulia Town (Table 1; Image 1a, b). Passeriformes was found to be the most dominant order represented by 46 species (Fig. 2). Among the families, Anatidae was represented by the highest of nine species ( Table  1). The residential status of the recorded birds shows that 78 species of birds were a permanent resident of Purulia, 36 bird species were winter migrants, and only one species Jacobin Cuckoo Clamator jacobinus was a summer migrant (Table 1). Among the winter migrants, Red-Crested Pochard Netta rufina, Northern Shoveler Anas clypeata, Garganey Spatula querquedula, Eurasian Wigeon Mareca penelope, Northern Pintail Anas acuta, Gadwall Mareca strepera, and Ferruginous Duck Aythya nyroca took shelter in the Saheb Bandh, Purulia. Among the 115 species of birds, 43 species were partly or completely dependent on water bodies.
The species richness value was highest in the winter season (104) and in December (99); whereas, this was lowest in Monsoon (69) and in August (61) ( Table 4). The overall avian diversity index (H′) for the town and surroundings was 3.66. The biodiversity index was also calculated month-wise ( Fig. 3) and it depicts that the Shannon-Wiener (H′) value was highest for January (1.564) though the H′ value does not differ significantly for the rest of the months. Shannon evenness (J′) value was lowest in December (0.767) and highest for July (0.857).

DISCUSSION
As evident from the present study, Purulia Town and its surrounding places nurture a widely diversified

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avian group with its arid environment, wild flora, the fragmented agricultural field, plantation, and gardens that provides a complex landscape. The study area is moderately rich with its avifauna with 115 species, and when compared with previous observations in different parts of India it has been found that the species richness at Purulia (Table 2) was lower than the values reported for Burdwan (144) (Hossain & Aditya 2016), and the surrounding area of western Kachchh (252) (Gajera et al. 2013). But the avian diversity was higher than that reported for Kolkata surroundings (48 species) (Sengupta et al. 2014). Shannon diversity index (H′) for the present study (3.66) was found to be higher than the Silent Valley (3.3) and moist deciduous forest of Mukkali (3.45) (Jayson & Mathew 2000), which indicates that Purulia Town possesses a rich avian diversity.
The present species richness value is greater than the richness values for Purulia Saheb bandh (24 species)    Though Purulia is an arid district, local aquatic bodies, especially Saheb Bandh and Kansai River, support the avian groups that dependent on aquatic habitat. The species richness value for the avian species was highest in winter, which is due to the presence of a large number of migratory birds especially in local water bodies like Saheb Bandh.
The resultant data reveals the functional roles and resource utilization patterns in the local ecosystem of the town. The availability of food resources is directly dependent on the precipitation rate and as an arid district of West Bengal, Purulia is severely deprived of water. Therefore, scarcity of water acts as a limiting factor for the survival of avian groups and a lesser number of granivores, herbivores, frugivores, and nectarivores throughout the year justifies the fact (Fig.  4). Interestingly, omnivores were highest in number followed by insectivores which might also be due to extreme weather conditions (Fig. 4). There are evidence about the influence of landscape on local species richness (Gaston 2000;Lawton 2000;Daube et al. 2003;Hossain & Aditya 2016).
As urbanization and developmental activities may destroy or degrade the natural habitats of birds therefore, there are urgent needs for the conservation of local habitats, including wetlands and water bodies.
Successful conservation of birds would require continuous monitoring by government authorities and awareness among local people. www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.

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