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Site description (2005 baseline)
Koshi Tappu Wildlife Reserve occupies 17,500 ha of the Sapta Koshi River floodplain at the most northeasterly extension of the Gangetic Plain. It ranges in altitude from 75-81 m (Green 1993). The reserve is located between two flood control embankments and is subject to annual flooding. Approximately 70% of the reserve's land area is covered in grasslands (Heinen 1993), although during high flood years a large area of grassland is destroyed and replaced by new alluvial deposits. Typha and Saccharum are major grassland types found here, although patches of Imperata and Phragmites are often seen (Peet et al. 1999a). Medium size phantas interspersed with young Acacia trees are found in sandy islands. Riverine vegetation with Acacia catechu/Dalbergia sissoo forest dominates on the islands and edges of the reserve. Mostly young trees grow inside and on the edges of the reserve within embankments, the old mature trees being swept away by annual floods. South of Koshi Tappu Wildlife Reserve lies the Koshi Barrage area. The area is 7 km from north to south and nearly 5 km from east to west. More than 50% of the land area at the barrage is covered by water, and the remaining land area is subject to intensive agriculture. The barrage gates are regulated by the Indian Government according to a 99-year lease agreement between Nepal and India.

Key biodiversity
The large number of 486 bird species has been recorded in the Koshi Tappu and Barrage area (Baral 2000c, Giri and Choudhary 2000ab, 2001ab, 2002abc, 2003ab, 2004ab, in prep., Tebb et al. 2004). Koshi is by far the most important wetland staging post for migrating waders and waterfowl in Nepal (Inskipp and Inskipp 1991) and was considered one of the most important in Asia (Scott 1989). Koshi Tappu also has the largest heronry in Nepal (Baral 1993), where as many as 25,730 nests belonging to 12 species of medium to large waders were reported in 1996 (Choudhary 1996b). As many as 20 globally threatened bird species have been recorded in the Koshi Tappu and Koshi Barrage area and eleven of these occur regularly. This IBA is especially important for some wetland and grassland species, notably Swamp Francolin Francolinus gularis, Baer’s Pochard Aythya baeri, Pallas’s Fish Eagle Haliaeetus leucoryphus, Greater Spotted Eagle, Imperial Eagle Aquila heliaca, Lesser Adjutant, Spot-billed Pelican and Bristled Grassbird Chaetornis striatus. It holds the largest population of the globally threatened Swamp Francolin in Nepal (Baral 1998a), and also supports a good population of the Bristled Grassbird (Baral in prep.). The site is also important for Nepal's near-threatened birds; 13 of the country’s total of 23 occur and eight of these are wetland birds. Only two restricted-range species have been recorded and both are rare visitors. A marked decline in wintering and passage migrant waterbird has been noted since 1990 and has been highlighted by the Annual Waterfowl Counts. In February 2003 a total of nearly 9,800 birds was counted at the site in one day, a very low number compared to twenty years ago when more than 50,000 birds were estimated (Choudhary 2003).

Non-bird biodiversity: The reserve contains Nepal's last population of Asian Buffalo Bubalus bubalis, a globally threatened species (Hilton-Taylor 2000). Other globally threatened species include Ganges River Dolphin Platanista gangetica, Nilgai Boselaphus tragocamelus, Smooth-coated Otter Lutrogale perspicillata, Gharial Gavialis gangeticus and Mugger Crocodile Crocodylus palustris (Hilton-Taylor 2000).

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Koshi Tappu Wildlife Reserve and Koshi Barrage (Nepal). Downloaded from https://datazone.birdlife.org/site/factsheet/koshi-tappu-wildlife-reserve-and-koshi-barrage-iba-nepal on 22/11/2024.