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The Sundarban is the largest delta covered with mangrove forests and vast saline mud flats in the world. It got the name from the mangrove plant locally known as Sundari Heritiera minor. The Sundarban stretches from the Hooghly (India) on the west to the Meghna (Bangladesh) in the east, both of which are major streams of the River Ganga. It spreads over the southern part of three districts, namely 24-Parganas (India), Khulna and Backarganj (Bangladesh). The boundary of Sundarban within West Bengal is demarcated by the Raimangal and Hooghly rivers in the East and West respectively, and the Bay of Bengal in the south. The northern limit cannot be clearly defined due to the progressive reclamation of land. The Sundarban covers an area of 9,63,000 ha, of which 2,58,500 ha is demarcated as the Sundarban Tiger Reserve and 1,33,000 as the National Park (core area). Sajnakhali Wildlife Sanctuary (36,234 ha) lies within the buffer zone, to the north of Netidhopani and Chadkhali forest blocks. There are two small sanctuaries within the Biosphere Reserve: the 583 ha Halliday Island Wildlife Sanctuary, and the 3,885 ha Lothian Island Wildlife Sanctuary. Sunderban is the largest mangrove forest, with perhaps the largest tiger population in the world. It is a World Heritage Site and Biosphere Reserve, both in India and Bangladesh. It is also proposed as a Ramsar site. This World Heritage site is known for its rich biodiversity, especially fish, crustaceans, reptiles and birds. The total area of the IBA extends over 4,26,200 ha, of which 2,32,000 ha is under mangrove forest and the remaining is under water (Mukherjee 1975). As reported earlier, Heritiera minor, locally known as Sundari (Jain and Sastry 1983) is a predominant feature of the IBA. Champion (1936) classified the Sundarban as Moist Tropical Seral Forest, comprising beach forest and tidal forests. Characteristic species include Rhizophora spp., Bruguiera gymnorhiza, Ceriops sp., and Avicennia officinalis. Heritiera minor is scattered over areas of higher elevation, along with Sonneratia apetala, Excoecaria agallocha, and Phoenix paludosa. Low mangrove forest (3-6 m high) occurs between Matla and Muriganga, to the west of the National Park and Tiger Reserve. This area is devoid of fresh water because its rivers are cut off from the ramifications of the Hooghly in the north. The soft mud of the intertidal zone supports a dense forest, very similar in composition to salt-water Heritiera forest. Various trees and other plants were introduced, including some exotics.
AVIFAUNA: Sanyal (2002) identified 163 species of birds from Sunderban but recently, Sujan Chatterjee (in litt. 2003) has listed 219 species. Although the whole of the Sunderban mangrove is a bird watcher’s paradise, Sajnakhali Wildlife Sanctuary is best known for its bird life. Mukherjee (1959) found 16 species in a breeding colony, including Darter Anhinga melanogaster and Black-necked Stork Ephippiorhynchus asiaticus (both presently Near Threatened). In India, Sunderban in the most important site for the Vulnerable Masked Finfoot Heliopais personata. It is difficult to estimate the total number of this elusive bird, but it is fairly common in suitable areas. Earlier, Greater Adjutant Leptoptilos dubius was commonly seen but now sightings are rare due to drastic decline in its numbers. Another uncommon species is the Spoon-billed Sandpiper Eurynorhynchus pygmeus, which is regularly reported from this site. As can be expected, Sunderban is famous for its waterbirds and water-dependent birds, such as the kingfishers. Out of the 12 kingfisher species found in India, six are found in this IBA. They are the Common Alcedo atthis, Brown-winged Halcyon amauroptera, Stork-billed H. capensis, Ruddy H. coromanda, White-throated H. smyrnensis, Black-capped H. pileata, Collared Todiramphus chloris and Pied Ceryle rudis Kingfishers. About 30 species of small waders (sandpipers, stints, plovers, curlews, etc.) and nine species of gulls and terns are found here. Sunderban is one of two sites where the Mangrove Whistler Pachycephala grisola is definitely found. This species is not considered threatened by BirdLife International (2001) as it is widely distributed in south and southeast Asia but its narrow, ribbon-like habitat along the coasts, that is under tremendous human pressure all over Asia, would put this species at risk in future. Incidentally, this is the only bird species that is entirely restricted to mangroves (Ali and Ripley, 1987, Grimmett et al. 1998). The vast Sunderban mangroves and mud flats host hundreds of thousands of waterbirds, especially waders but as we do not have species-wise detailed information, we have not listed this site under any A4 criteria. This site is selected only on the basis of presence of globally threatened species (A1 criteria).
OTHER KEY FAUNA: Although seldom seem, the Tiger Panthera tigris is the star attraction of Sunderban. Sunderban also has the largest population of the Estuarine Crocodile Crocodylus porosus. A hundred years ago the Sundarban Forests were the home of many wild animals, including the Javan Rhinoceros Rhinoceros sondaicus, Swamp Deer Cervus duvauceli, Chital Axis axis, Wild Boar Sus scrofa, Rhesus Macaque Macaca mullata, Fishing Cat Felis viverrina, and Wild Buffalo Bubalus arnee. It is said that Barking Deer Muntiacus muntjak existed on these swamp islands, but it has not been recorded in recent years from the Sundarban Forests that lie in West Bengal.
BirdLife International (2019) Important Bird Areas factsheet: Sundarbans Biosphere Reserve (National Park). Downloaded from http://www.birdlife.org on 18/11/2019.