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Location India, Assam
Central coordinates 95o 28.50' East  27o 16.00' North
IBA criteria A1, A2
Area 46,775 ha
Altitude 120 - 474m
Year of IBA assessment 2004

Bombay Natural History Society

Site description This complex includes six Reserve Forests and three proposed Reserve Forests, all contiguous with each other. The areas constituting this IBA are Upper Dihing (27,500 ha), Joypur (10,870 ha), Dirak including additions (3,708 ha), Dilli (3,030 ha), Makumpani including additions (538 ha), Desali (200 ha), Digboiwest block (929 ha). Together they form the largest contiguous tropical rainforest area extant in the whole of Brahmaputra Valley (Choudhury 1996a). Of these, the Upper Dihing (West Block) has a long history of protection and management as a Reserve Forest, which was notified more than a century ago, in 1888. Some of the finest rain forests on flat plains in India are seen here. The area varies from slightly undulating plains in Upper Dihing to hills in Joypur, Dirak and Dilli, which are the foothills of the Patkai Range. The habitats in Dilli, Joypur and Dirak are contiguous with the forests of Arunachal Pradesh. Burhi-Dihing is the main river flowing through the site. Other notable rivers are Disang or Dilli, Dirak, Namsang and Digboi. Many small perennial streams criss-cross the area, noteworthy are the Janglu and Pawoi nullahs. These forests, especially Upper Dihing (West Block) have the largest known population of the globally endangered White-winged Duck Cairina scutulata (Choudhury 1996a, 1998). Together with other forests, the estimated population is higher than in any IBA in the world (BirdLife International 2001, Choudhury 2000). This area is also rich in primates and was recommended for protected area status way back in the 1980s (Choudhury 1989). Five species of hornbills occur in the area, including the rarer Brown Hornbill Anorrhinus tickelli and the Rufous-necked Hornbill Aceros nipalensis. Soraipung (meaning ‘bird spring’) in Upper Dihing is a well-known site for the Asian Elephant Elephas maximus and avifauna. The habitat is Tropical Rainforest. Champion and Seth (1968) described it as ‘Assam Valley Tropical Wet Evergreen Forest’. Arundo donax, Imperata cylindrica and Saccharum spp. occur in the scattered swampy/marshy depressions.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
White-winged Duck Asarcornis scutulata resident  2004  present  A1  Endangered 
Lesser Adjutant Leptoptilos javanicus resident  2004  present  A1  Vulnerable 
White-bellied Heron Ardea insignis resident  2004  present  A1  Critically Endangered 
White-rumped Vulture Gyps bengalensis non-breeding  2004  present  A1  Critically Endangered 
Slender-billed Vulture Gyps tenuirostris non-breeding  2004  present  A1  Critically Endangered 
Pale-capped Pigeon Columba punicea resident  2004  present  A1  Vulnerable 
Rufous-necked Hornbill Aceros nipalensis resident  2004  present  A1  Vulnerable 
Yellow-vented Warbler Phylloscopus cantator 2004  present  A2  Least Concern 
Beautiful Nuthatch Sitta formosa resident  2004  present  A1  Vulnerable 


IUCN habitat Habitat detail Extent (% of site)
Forest   -
Wetlands (inland)   -
Artificial - terrestrial   -

Land use

Land-use Extent (% of site)
agriculture -
Notes: Agriculture
forestry -
Notes: Forest
urban/industrial/transport -
Notes: Industry (oil installations)

Acknowledgements Key contributors: Anwaruddin Choudhury, Kulojyoti Lahkar and Mridu Paban Phukan.


Alstrom, P., Jirle, E., Jaderblad, M., Kjellen, N., Larsson, G., Paulsrud, A., Saellstrom, J., Smitterberg, P. and Alind, P. (1994) Birds and Mammals observed in Assam in Feb. 1994. Unpublish report.

Baker, E. C. S. (1908) The Indian Ducks and their Allies. First edition. Bombay Natural History Society/ R.H.Parker, London. xi + Pg 292.

BirdLife International (2001) Threatened Birds of Asia: The BirdLife International Red Data Book. BirdLife International, Cambridge, U.K.

Champion, H. G. and Seth, S. K. (1968) A revised survey of forest types of India, Govt. of India Press, Delhi.

Choudhury, A. U. (1989) The Primates of Assam, their distribution, habitat and status. Unpublished Ph.D. thesis, Gauhati University. Pp. 300 + maps.

Choudhury, A. U. (1996a) Survey of the White-winged Wood Duck and Bengal Florican in Tinsukia district and adjacent areas of Assam and Arunachal Pradesh. The Rhino Foundation for Nature in NE India. Guwahati.

Choudhury, A. U. (1996b) Survey of primates in some parts of eastern and central Assam. Final Report to ASTEC, Guwahati. 32pp. + maps.

Choudhury, A. U. (1998) Status and conservation of the white-winged duck in eastern Assam, India. OBC Bulletin 28: 14-17.

Choudhury, A. U. (2000): The Birds of Assam, Gibbon Books & WWF India NE Region, Guwahati. Pp. 240.

Hume, A. O. and Marshall, C. H. T. (1879-1881) The game birds of India, Burmah and Ceylon- 3 Vols. Authors, Calcutta.

Lahkar, K. (2001) Birds of Upper Dihing (East Block) and Kakojan Reserved Forests and Digboi Forest Area Report to the Bombay Natural History Society, Mumbai. (Unpubl.) 30pp. + 1 map.

Parsons, R. E. (1939) Migration routes of Geese. J. Bombay Nat. Hist. Soc. 40(4): 764-765.

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Recommended citation  BirdLife International (2014) Important Bird Areas factsheet: Upper Dihing (West) Complex. Downloaded from on 24/10/2014

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