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Site description (2004 baseline):

Bison Swamp is located at the southwest end of Nilgiris district, Tamil Nadu, very close to the Kerala border. It is a part of the Korakundah Range of the Nilgiris South Forest Division. Francis (1908) in the Nilgiri Gazetteer describes the origin of its name, from the congregation of Indian Bison or Gaur Bos frontalis, which the early settlers often hunted. During the last century, Bison Swamp experienced extensive habitat changes affecting its flora and fauna. It was extensively planted with exotics such as Eucalyptus globulus and Wattle Acacia mearnsii. A very small proportion of natural shola and grassland remains. Despite habitat loss and degradation, this IBA is still important for the conservation of endemic and threatened birds such as the Nilgiri Laughingthrush Garrulax cachinnans. Natural vegetation of this site can be classified into two major types namely, Southern Montane Wet Temperate Forest (shola), and grasslands. Both have been converted to plantations. Patches of grasslands, between plantation and shola patches, remain in Bison Swamp. Plantations of Wattle and Eucalyptus now occupy a major portion of Bison Swamp. Wattle forms impenetrable thickets, severely affecting the movement of larger mammals. It regenerates and spreads quickly, and may be termed invasive.

AVIFAUNA: Bison Swamp was once home to a wintering population of Wood Snipe Gallinago nemoricola and Eurasian Woodcock Scolopax rusticola, but these species have become rare owing to severe hunting pressure as game birds during the early decades of the 20th century, followed by habitat degradation. The Shola around the swamp harbours a number of Western Ghats endemics and habitat specialists such as the Nilgiri Laughingthrush, Nilgiri Wood-Pigeon Columba elphinstonii, Nilgiri Flycatcher Eumyias albicaudata, Nilgiri Pipit Anthus nilghiriensis, Black-and-Orange Flycatcher Ficedula nigrorufa and Small Sunbird Nectarinia minima, among others. The details of birds seen around this site are given by Zarri et al. (2002). The site lies in Biome-10 (Indian Peninsula Tropical Moist Forest), but many species of other biomes are also found in winter. The biome species recorded in this IBA are: Tickell’s Leaf Warbler Phylloscopus affinis (Biome-5: Eurasian High Montane); Largebilled Leaf Warbler Phylloscopus magnirostris and Indian Blue Robin Luscinia brunnea (Biome-7: Sino-Himalayan Temperate Forest); Black Bulbul Hypsipetes leucocephalus (Biome-8: Sino- Himalayan Subtropical Forest); White-cheeked Barbet Megalaima viridis and Indian Scimitar Babbler Pomatorhinus horsfieldii (Biome-10) and Common Indian Nightjar Caprimulgus asiaticus, White-eye Buzzard Butastur teesa, Painted Bush Quail Perdicula erythrorhyncha, White-browed Fantail-Flycatcher Rhipidura aureola, Lesser Golden-backed Woodpecker Dinopium benghalense and Ashy Prinia Prinia socialis (Biome-11: Indo- Malayan Tropical Dry Zone).

OTHER KEY FAUNA: Ironically enough, the Bison or Gaur has become uncommon in Bison Swamp! Only a few are seen, during the monsoon. Both Tiger Panthera tigris and Leopard P. pardus are frequently seen in this IBA, their prey Sambar Cervus unicolor and Barking Deer Muntiacus muntjak being fairly common. Asian Elephants Elephas maximus cross through this area, like many other IBA of the Nilgiris, during their annual migration from Silent Valley to the Wynaad Plains. Other mammals include Jungle Cat Felis chaus, Brown Palm Civet Paradoxurus jerdoni, Striped-necked Mongoose Herpestes vitticollis Common Mongoose Herpestes edwardsi, Wild Dog Cuon alpinus, Golden Jackal Canis aureus, Nilgiri Langur Trachypithecus johni, and Wild Boar Sus scrofa. Nilgiri Marten Martes gwatkinsi may also be present, but there is no recent record.

MAIN THREATS: Invasive species; Grazing; Firewood collection; Poaching.

The key conservation problem that has changed the ecological landscape of this area is conversion of natural vegetation into exotic plantations. Commercial timber harvesting is another major problem. Remnant grassland patches are vulnerable to burning during summer. As Bison Swamp is on the border of Tamil Nadu with Kerala State, there is lot of illegal cultivation of Cannabis sativa (Ganja). Animal poachers also take advantage of its remoteness, tough terrain and inaccessibility. Inclusion of this site in the proposed expansion of Mukurthi National Park may save it from further exploitation. There is urgent need to stop degradation of natural habitats around Bison Swamp.

Key contributor: Ashfaq Ahmed Zarri.

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Bison Swamp (Nilgiri) (India). Downloaded from https://datazone.birdlife.org/site/factsheet/bison-swamp-(nilgiri)-iba-india on 23/12/2024.