Upper Dihing (East) Complex

Year of compilation: 2004

Site description
Upper Dihing (East) Complex includes four reserve forests, namely Upper Dihing (East Block) including the area leased to oil fields (13,168 ha), Kakojan (2,345 ha), Duarmara (653 ha) and Torani (2,040 ha) Reserve Forests. The Upper Dihing (East Block), Kakojan and Digboi Oil field areas are contiguous, while Torani and Duarmara are isolated areas some distance away. These forests are among the last remaining patches of Tropical Evergreen Forests of some significance in Assam. The area consists of slightly undulating plains. Dibru, the main river, flows through the Upper Dihing and Kakojan Reserve Forests. Many small perennial streams criss-cross the area, notably the Kharjan river. Small jungle pools and natural or artificial swampy areas are also present (Lahkar 2001). These forests are globally important, as a sizeable number of the Whitewinged Duck Cairina scutulata is found here (Choudhury 1996, 1998). There are also relatively recent reports of the Masked Finfoot Heliopais personata from this site (Choudhury 1997). There is also a past record of the Baikal Teal Anas formosa (Hooper 1958). The vegetation of the site is mainly Tropical Wet Evergreen Rain Forest type. The important tree species are Dipterocarpus macrocarpus, Shorea assamica, Mesua ferrea, Terminalia myriocarpa, Artocarpus chaplasha, Dillenia indica, Anthocephalus cadamba, Bombax ceiba and Ficus spp. Scattered marshy depressions bear Alpinia allughas, Arundo donax, Imperata cylindrical and Saccharum spp. Tectona grandis is seen on roadside plantations (Lahkar 2001).

Key biodiversity

AVIFAUNA: About 300 species of birds are reported from the site that includes threatened species such as the White-bellied Heron Ardea insignis and Purple Wood or Pale-capped Pigeon Columba punicea (Lahkar 2001). The Malay Fish-Owl Bubo ketupu has also been recorded (Lahkar 2002). Some interesting species of various biomes are: White-cheeked Hill Partridge Arborophila atrogularis, Grey Peacock Pheasant Polyplectron bicalcaratum, Masked Finfoot, Bamboo Partridge Bambusicola fytchii, Pale-headed Woodpecker Gecinulus grantia, Crowbilled Drongo Dicrurus annectans, Black-gorgeted Laughingthrush Garrulax pectoralis, Black-backed Forktail Enicurus immaculatus, Spotted Wren Warbler Spelaeornis formosus, Rufousbellied Niltava Muscicapa sundara, Dull Slatybellied Ground Warbler Tesia cyaniventer, Pied Falconet Microhierax melanoleucos, Grey-headed Parakeet Psittacula finschii, Blyth’s Kingfisher Alcedo hercules, Brown Hornbill Anorrhinus tickelli, Rufous-necked Hornbill Aceros nipalensis, Golden-throated Barbet Megalaima franklinii, Blue-throated Barbet M. asiatica, Bay Woodpecker Blythipicus pyrrhotis, Bluenaped Pitta Pitta nipalensis, Maroon oriole Oriolus trailii, Black-browed Treepie Dendrocitta frontalis, Himalayan Treepie D. formosae, Smaller Grey Cuckoo Shrike Coracina melaschistos, Short-billed Minivet Pericrocotus brevirostris, Orange-bellied Chloropsis Chloropsis hardwickii, Whitethroated Bulbul Criniger flaveolus, Spot-throated Babbler Pellorneum albiventre, Nepal Babbler Alcippe nipalensis, Slatybacked Forktail Enicurus immaculatus, Black-breasted Thrush Turdus dissimilis and Red-headed Tit Aegithalos concinnus. Other interesting birds, the Chinese Pond Heron Ardeola bacchus, rarely seen in eastern Assam, was recorded in October, 2000; the Malay or Tiger Bittern Gorsachius melanolophus was also seen in October 2000 (Lahkar 2001). More than 30 Ferruginous Pochards Aythya nyroca were counted in Digboi Oil Field in February 2000 (Lahkar 2001). The Masked Finfoot is a rare bird all over its range from northeastern India to Malaya and Sumatra. It is a shy and secretive bird inhabiting wetlands inside the rainforests, preferring similar habitat as the White-winged Duck Cairina scutulata. Many local villagers and forest staff are not aware of any such bird although they are familiar with the Whitewinged Duck (Choudhury 1997). Individuals were seen near Dhekiajan forest village of Upper Dihing (East Block) RF in 1990-91 by Robin Sonowal and in Dibru river near Nazirating, just outside the boundaries of the Kakojan and Upper Dihing (East Block) RF in August-September 1992 by T. Moran (Choudhury 1997). The Golden Plover Pluvialis apricaria is an uncommon winter visitor in Assam. Five birds were seen near Kherjan forest village just outside the Upper Dihing (east block) RF. This is the second record for the state (Choudhury 2000, Lahkar 2001). Individuals of the Pale-capped Pigeon Columba punicea were also reported from this IBA, mainly in the Upper Dihing (East Block) RF (Lahkar 2001). Malay Fish-Owl or Buffy Fish Owl was also reported from Upper Dihing RF almost after 100 years (Lahkar 2001).

OTHER KEY FAUNA: Mammalian fauna of the site includes Tiger Panthera tigris, Leopard P. pardus, Asian Elephant Elephas maximus, Hoolock Gibbon Hylobates hoolock, Capped Langur Trachypithecus pileatus, Pigtailed Macaque Macaca nemestrina, Rhesus Macaque M. mulatta, Slow Loris Nycticebus coucang, Gaur Bos frontalis, Golden Jackal Canis aureus, Wild Dog Cuon alpinus, Malayan Giant Squirrel Ratufa bicolor, Common Giant Flying Squirrel Petaurista petaurista, Sambar Cervus unicolor and Barking Deer Muntiacus muntjak. Not much is known about reptiles and amphibians.

Pressure/threats to key biodiversity
MAIN THREATS: Pollution from oil mining; Expansion of oil drilling; Illegal felling of trees; Illegal fishing and Poaching; Encroachment.

The main problem is oil drilling that extends over larger parts of Upper Dihing (East Block) RF. Many of the waterbodies near the oil rigs are heavily polluted, posing serious threat to the environment. Illegal felling of trees, encroachment by forest villagers and surrounding villagers, and poaching including collection of eggs and ducklings of the White-winged Duck, are other major issues. There is an urgent need to control poaching, better management of the Reserve Forests, environmental awareness amongst villagers and the people from the oil refineries. The White-winged Duck could become a focal point for the conservation of these excellent tropical moist forests.

Key contributor: Kulojyoti Lahkar.

Recommended citation
BirdLife International (2022) Important Bird Areas factsheet: Upper Dihing (East) Complex. Downloaded from on 12/08/2022.