Diversity of wintering avifauna throughout the heterogeneous aquatic habitats of Bankura District, West Bengal, India

: Birds play various crucial roles in the ecosystem including pollination, seed dispersal, and pest control. Assemblages of bird species in a particular landscape are useful predictors in various ecosystem services, this is evident from studies of forest bird assemblages, aquatic bodies and agro ecosystems. For developing conservation strategies, information on bird species assemblages in a particular geographical area is important. Diversity in aquatic ecosystem support a diversity of water bird species. In the present study, around 45 bird species were recorded in 21 aquatic bodies in Bankura, West Bengal, India, in which two species, namely, Leptoptilos javanicus and Aythya ferina declared ‘Vulnerable’ and three species such as Mareca falcata, Threskiornis melanocephalus , and Limosa limosa considered as ‘Near Threatened’ according to the IUCN Red list. Dendrocygna javanica and Nettapus coromandelianus were found to be the most abundant. In those 21 study areas, site6 has the highest species richness and site2 has the lowest. The dominance index was highest for site2 and lowest for site6. Pielou’s index of evenness was highest for site20. The rarefaction curve showed species abundance was highest for site1. Classical cluster analysis for species abundance showsthat site20, site21, site3, site8, site4, site19, site5, site14, site12, site15, site7, site 10 site11, and site13 are closely related. This paper is aimed to generate interest among people to conserve aquatic birds and their habitats and to document baseline information for further study.


INTRODUCTION
Birds are one of the most popular life forms on the planet and their diversity contributes to life's richness and beauty.Birds are important components of the ecosystem contributing substantively toecosystem function, especially pollination, seed dispersal, pest control, nutrient cycling, and others (Whelan et al. 2008;Sekercioglu 2012).Information on bird assemblages in forests (Aich & Mukhopadhyay 2008;Roy et al. 2011;Chatterjee et al. 2013), aquatic bodies (Kumar et al. 2006;Kumar & Gupta 2013), agricultural and otherlandscapes are useful tools in understanding the various ecosystem health (Dhindsa & Saini 1994;Borad et al. 2001;Basavarajappa 2006;Gopi Sundar 2011;Gopi Sundar & Kittur 2013;Hossain & Aditya 2014) and to develop strategies for conservation and further monitoring of ecosystem conditions and functions (Bradford et al. 1998;Browder et al. 2002).Millions of people rely on aquatic ecosystems for a better living through fishing, agricultural irrigation and other purposes.Birds can be found almost everywhere on the planet, in almost every climatic condition and at nearly every altitude.Birds are excellent environmental indicators because they respond quickly to changes in habitat structure, composition and other environmental factors (Hossain & Aditya 2014).Besides their aesthetic role, they also hold a unique position in the food chain.Aquatic ecosystems are highly productive ecosystems on Earth and provide people a source of food, animal farming, fisheries, aquaculture and also as a refuge for rare and endangered plant and animal species.The assemblage of foraging bird species is dependent on habitat type and stable condition of food resources.Migratory birds also play an important role in maintaining ecosystem health by influencing nutrient cycling during the migratory season.The present study deals with the documentation of avifauna in Bankura and similar areas in the Chota Nagpur Plateau.The study sites are heterogeneous in habitat structure as some of the aquatic bodies are in plains area while others are from hilly terrains, and forested areas while some from agricultural areas and a few of them are within the human settlements.The climate of the Bankura District is characterized by excessive heat in summer and highly humid throughout the year.The average daily maximum temperature varies 26-39 0 C during summer and during winter temperature ranges 12-25 0 C. The relative humidity is high throughout the year.Damodar, Dwarakeswar, Silabati, and Kangsabati are the four major rivers of Bankura District.These rivers constitute the main drainage system of this district.The Kangsabati dam is a major dam constructed on the river at Mukutmanipur of Bankura District to arrest flood and to provide irrigation facilities.There are many threats to the water bodies of Bankura that include pollution due to domestic sewage, pesticides, fertilizers, farming agriculture along the exposing periphery, eutrophication/blooms of surface water, partial reclamation of wetland, residential & commercial development, and sedimentation that are the primary factors for reducing species diversity including birds.
The current study's goal was to assess the diversity of wintering aquatic birds and create an avifauna checklist for the district of Bankura, West Bengal, India, which will aid in future aquatic bird management with appropriate conservation strategies.
Lal Bandh: Fresh water lake with 30% vegetation cover, including shrubs, reeds, Hydrilla, water hyacinth, and water lilies.The lake has a surface area of about 12 ha and a maximum depth of about 9 m.
Jamuna Bandh: This freshwater lake covers an area of 22 ha, with vegetation covering 90% of the area.This aquatic body has a maximum depth of approximately 8 m.
Krishna Bandh: Relying completely on rainfall and local streams, this freshwater lake spans 10 ha in surface area with a maximum depth of 5 m.Notably, 30% of the area hosts vegetation, including submerged Hydrilla, Kulaijurir bandh: This freshwater pond covers an area of 18 ha and has a maximum depth of about 5 m; 56% of the area is covered by vegetation, which includes various shrubs on the bank, free-floating water hyacinth, and submerged Hydrilla.
Sal bandh: Sal bandh is a 3.5-ha reservoir with a maximum depth of 3 m.It is dependent on local rain and is only temporary in nature.Vegetation covered 20% of this area.
Kadam Deuli dam: Featuring a 7 m maximum depth, this rainwater and stream-fed freshwater pond spans a total area of 14.94 ha.Impressively, 86% of this expanse is veiled by vegetation.
Sutan dam: This reservoir has a surface area of 6.5 ha and a maximum depth of 4 m.It is primarily dependent on rainfall and streams.Vegetation such as Hydrilla and various shrubs covered 15% of the area.
Gangdua dam: This lake's main source of water is local rainfall and streams.This body of water has an area of about 18 ha and a maximum depth of 7.5 m.Hydrilla and water lily vegetation covered 35% of the area.
Bonkati bandh: The main sources of water for this freshwater lake are local rainand streams.This water body covers an area of11.92ha and has a maximum depth of about 5 m.The vegetation covered 66% of the land area.
Bagjobra bandh: This lake covers 5 ha, and 86% of it Talberia dam: Talberia dam is a freshwater lake with a surface area of 12.30 ha and a maximum depth of 5 m.It is reliant on rainwater and streams, and vegetation covers 53% of the area, including various shrubs in the bank, Hydrilla, water hyacinth, and water lilies.
Kakila Daha: Local rainwater and streams are the primary sources of water for this lake, which has a maximum depth of 5 m.This lake took up 4.94 ha of land, accounting for 39% of the total vegetation area.
Jhilimili bandh: This freshwater lake has a surface area of 12.37 ha and a maximum depth of 5.5 m.It is entirely dependent on rainwater and streams for its survival.The vegetation covered 66% of the land area.
Poabagan bandh: Spanning an area of 4.514 ha, this site relies on local rainfall and streams for sustained existence.Vegetation, encompassing shrubs, reeds, Hydrilla, and water hyacinth, blankets 46% of the area.
Chattna bandh: This freshwater lake has an area of 11.30 ha, with vegetation covering 69% of it.Its long-term survival is dependent on local rains and streams.
Nityanandapur dam: With a surface area of 24 ha and a maximum depth of 7 m, this reservoir relies on rainfall and local streams.About 90% of its area features vegetation, including various shrubs, Hydrilla, and water lilies.
Ambikanagar bandh: This freshwater lake, fed by local rain and streams, spans an area of 18 ha with a maximum depth of 12 m.Approximately 90% of the area is covered by vegetation Saheb bandh: A freshwater lake with a surface area of 9.2 ha and a depth of 6 m.It is mainly dependent on local rainfall and stream flow.The area is covered by vegetation, accounting for 49% of the total area.This vegetation includes primarily shrubs growing along the banks, as well as submerged and free-floating aquatic plants.
Ranir bandh: This lake is seasonal in nature and relies on water from streams.It spans an area of 3 ha and has a maximum depth of 5 m.Vegetation covers 20% of the total area surrounding the lake.

Data Collection
The survey spanned from November to January in both 2018 and 2019, involving monthly visits to study sites from 0700 h to 1200 h and 1230 h to 1700 h with the participation of nine individuals.Transportation primarily relied on bicycles and motorcycles to cover the extensive distances.Executed through the point count method, the survey focused on cataloging bird species around water bodies and their environs.Birds were observed using Olympus 7 X 21 PS III binoculars and documented via Nikon Coolpix P600 camera.Identification of avian species utilized relevant keys from Grimmett et al. (1998), Kazmierczak & van Perlo (2000), and Ali (2002)

Statistical Analyses
Three biological indices are employed to compute species richness, species dominance, and evenness: the Shannon-Wiener index (Shannon & Wiener 1963), the Berger-Parker index (Berger & Parker 1970), and Pielou's index (Pielou 1969;Biswas et al. 2019;Mukherjee et al. 2021).The Shannon-Wiener index (Shannon & Wiener 1963) serves as a valuable statistical metric for determining the species richness within a community.This index can yield low values due to the contribution of rare species with small populations.The calculation is expressed as Hs = -Ʃpi ln pi, where Hs represents the Shannon index value and pi signifies the proportion of the ith species within the community.The Berger-Parker index (Berger & Parker 1970) is derived as d = max(pi), where d indicates dominance and pi denotes the proportion of the i th species in the community.Higher values of the Berger-Parker index imply greater dominance by one or a few species.Pielou's index of species evenness (Pielou 1969) gauges how evenly species are distributed numerically within the community.The following formula quantifies it: E = Hs / Hmax, where E signifies evenness, Hs signifies the Shannon index value, and Hmax represents ln(S), where S signifies the number of species in the community.Pielou's evenness index ranges from 0 to 1, with values closer to 1 indicating higher species evenness in the community.All three indices underwent one-way ANOVA to assess the significance of differences in their means.Subsequently, the species-habitatevenness (SHE) analysis was employed to interpret the relationship between species richness (H) and evenness (E) of the samples.This analysis was carried out to understand the log series distribution of species in the community.Furthermore, principal component analysis (PCA) was performed on the Shannon-Wiener index of species richness, Pielou's index of evenness, and the Berger-Parker index of dominance to elucidate the relationships between these three variables.For the species abundance across all 21 sites, classical clustering using the UPGMA algorithm (based on the Brey-Curtis index)

RESULTS
In Bankura, 45 species of aquatic birds were recorded during winter in 21 different locations (Table 1).The results of one-way ANOVA for the Shannon-Wiener index (F = 11.06,p <0.001) (Table 2), Berger-Parker index of dominance (F = 6.519, p <0.001) (Table 2) and Pielou's index of evenness (F = 27.92,p <0.001) (Table 2) demonstrated that there was a significant difference in the mean of all the indices present in all of the study sites.The Shannon-Wiener index, or species richness, was highest at site 6 (2.280±0.10)and lowest at site 2 (0.82±0.015) (Figure 2).These findings indicate that the community at site 6 is a natural one with high species richness.As the dominance index increases, species richness decreases because the highest dominance index recommends the predominance of one or a few species in an ecosystem.Site 2 has the highest dominance index (0.84±0.13) and Site 6 has the lowest (0.32±0.04) (Figure 3).The highest species evenness (0.91±0.06) is found at Site 20 (Figure 4).The results of SHE analysis show a log-series distribution of bird species in the studied area (Figure 5).Individual rarefaction analysis of taxa plotted at the 95 percent confidence level shows that the highest specimen is more likely to be found in site 1, followed by site 2 (Figure 6).PCA results show that dimension 1 has an Eigen value of 2.04390180, followed by dimension 2 with a value of 0.92147965; in terms of percent variance, dimensions 1 and 2 contribute 68.130060 and 30.715988, respectively (Table 3).The PCA scree plot shows that dimensions 1 and 2 contribute the majority of the percent variance (Figure 7).In terms of species abundance, classical cluster analysis using the Brey-Curtis index reveals that sites 20-site 21, site 3, site 8, site 4, site 19, site 5, site 14, site 12, site15, site7, site 10 and site 11, site 13 are closely related (Figure 8).

DISCUSSION
During the current study, 45 bird Species of 13 families such as Accipitridae, Alcedinidae, Anatidae, Ardeidae, Charadriidae, Ciconiidae, Jacanidae, Motacillidae, Phalacrocoracidae, Podicipedidae, Rallidae, Scolopacidae, and Threskiornithidae were recorded in aquatic bodies in the Bankura district, including two 'Vulnerable' species Leptoptilos javanicusand Aythya farina, three      'Near Threatened' species Mareca falcata, Threskiornis melanocephalus and Limosa limosa as listed under Dendrocygna javanica and Nettapus coromandelianus are the most abundant.This is the first report of its kind on birds in 21 aquatic bodies and their surroundings in Bankura.Birds are vulnerable to changes in the landscape, pollution, hunting and other factors, so proper precautions must be taken to protect them.The Shannon-Wiener index is highest at site 6 and lowest at site 2, and the Berger-Parker index is highest at site 2 and lowest at site 6.Site 20 has the highest level of evenness.
The results of SHE analysis show that the distribution of bird species in the studied area is a log series.The rarefaction curve depicts the likelihood of finding the most specimens at site 1, followed by site 2. The richness value observed during the current survey is higher than the values reported in 2000 for Purulia Saheb bandh (24 species) (Nandi et al. 2004) , 16, 15, 14, 12, 12, 10, 10, 8, 6, 6, 5, 6, 5, 5, and 5 species, respectively.The present study investigates that the reduction in richness value may be due to pollution by domestic sewage, pesticides, fertilizers, eutrophication and residential & commercial development in the bank of these aquatic bodies.The loss of avian diversity can have a significant impact on species interactions and ecosystem functions.Changes in avian diversity have an impact on the food chain (Hossain & Aditya 2014).Assessing avifauna assemblages to govern foraging behaviour and habitat preferences is critical for determining their importance in ecosystem services (Lawton et al. 1998;Sekercioglu 2006).It was observed that species richness values were lower for the Mukutmanipur dam, Jamuna bandh, Krishna bandh, and Kulaijurir bandhbut richness value was higher for Lal bandh than the previous survey (Nandi et al. 2004).A survey of sixteen new aquatic bodies was conducted that had not previously been done (Nandi et al. 2004).So, to begin the assessment of ecological services in a specific landscape, a document of species richness and composition of birds must be created and maintained as present study.This document aids in the comparison of aquatic bird diversity for future research.The primary step in the conservation of bird species and the maintenance of ecosystem services is the species-specific ecological role, which is far from complete in the Indian context (Dhindsa & Saini 1994;Singh &Banyal 2013;Sengupta et al. 2013;Sundar & Kittur 2013).This report can pique people's interest in conserving aquatic birds and their habitats and conservation of this avifauna is necessary for long-term development.

Figure 1
Figure 1.a-Coordinates of study area plotted in India State map | b-Raster plot of West Bengal | c-Raster plot of Bankura District.

Figure 2 .
Figure 2. Ggplot of Shannon-Wiener index showing Site 6 has the highest and Site 2 has the lowest species richness.

Figure 3 .
Figure 3. Ggplot of Berger-Parker index of dominance showing Site 2 has the highest and Site 6 has the lowest dominance.

Figure 4 .
Figure 4. Ggplot of Pielou's index of evenness showing site 20 has the highest species evenness.