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The study was carried out in Kanwar wetland (Figure 2.4), one of the largest inland freshwater lakes in the Indo‐Gangetic biogeographic zone. It was formed naturally by the meandering of the Burhi Gandak River in the geologic past (Rodger and Panwar 1988a, b). It was declared as a Wildlife Sanctuary in 1989 by the Ministry of Environment and Forest, Government of India. Geographically, it is located between (25°35^′00″ – 25°40^′00″ N and 86°05^′00^″ – 86°10^′00″ E) and covering an area of 6311 ha. It is classified as wetland type 19, because of the type of wetland habitat present, i.e. paddies (Scott 1989). It is a flat terrain with an average elevation of 44 m above mean sea level. This area is found in the tropical wet zone of India (Sarthi and Singh 2013), and temperature varies in a range of 7–38 °C. It mainly experiences four distinct seasons of winter (December–February), summer (March–May), monsoon (June–August), and post‐monsoon (September–November). The average annual rainfall is 1100 mm mainly received from the southwest monsoon between July to September. It often gets recharged either from rainwater or excess water from the river Burhi Gandak during the monsoon period. It was identified as a lake of national importance and included in the National Wetland Conservation Programme by the Ministry of Environment and Forest, Government of India in 2009.

Figure 2.4 A map of (a) India, (b) Bihar, and (c) study area with sampling locations.

The wetland supports a large variety of micro‐ and macro‐flora and fauna in and around its boundary. The vegetation around the wetland area is characterized by tropical dry mixed forest, tropical seasonal swamp forests, and wooded grasslands (Champion and Seth 1968). The major tree species Peepal (Ficus religiosa), Indian Banyan (Ficus benghalensis), Cluster fig (Ficus racemosa), White fig (Ficus infectoria), Babool (Acacia nilotica), Sissoo (Dalbergia sissoo), Arjuna (Terminalia arjuna), and so on support the shoreline and raised mounds or rahies. Common reed (Phragmites karka), water hyacinth (Eichhornia crassipes), lotus (Nelumbo nucifera), Hydrilla (Hydrilla verticillata), and Sesbania species are the most prominent aquatic species of this wetland (Rakshi and Sanghi 1996).

The wetland is an important waterfowl habitat of different residential (107 species) and migratory (59 species) birds (Ramakrishna et al. 2002). The white‐rumped vulture (Gyps bengalensis), the Indian vulture (Gyps indicus), the greater spotted eagle (Aquila clanga), and the Sarus crane (Grus antigone) are the most threatened bird species in this lake (Collar 2005). Different wild animals like blue bulls (Boselaphus tragocamelus), bats (Chiroptera), squirrels (Sciuridae), and jackals are often visible in the late monsoon seasons (Rakshi and Sanghi 1996).

More than 16 hamlets are situated around the wetland. These hamlets were less populated and mainly dominated by the local community during the late 1980s. They were completely dependent on the lake for fishing, bird capture, fuelwood, livestock grazing, and wetland paddy cultivation for their livelihoods (Rodger and Panwar 1988a; Rakshi and Sanghi 1996). Nowadays, the population has drastically increased because of the movement of other communities. During the late monsoon season, when the water recedes, the people cultivate different crops on the open areas of the wetland. The four crop seasons are Kharif (August–November), Rabi (November–February), Aghani, and Garma (March–May). Major crops such as paddy, sugarcane, wheat, maize, pulses, and different vegetables are commonly cultivated. In addition, a practice of double cropping pattern is also common.