This large Tropical Wet Evergreen Forest area is little explored by scientists. It lies adjacent to Assam’s Upper Dihing (West Block) and Joypur Reserve Forests. The forest is dominated by tall dipterocarps, especially Hollong (Dipterocarpus macrocarpus), which grows up to 50 m. The area is hilly, being part of Patkai Range, is known for the rare White-winged Duck Cairina scutulata.
AVIFAUNA: Not much is known about the bird life, except for the presence of White-winged Duck (Choudhury 1996, 2002), a globally threatened species (BirdLife International 2001). According to Choudhury (pers. comm. 2003), a sizeable population of White-winged Duck occurs in this IBA. In 1993, two ducks were seen in a nullah (stream), about 0.5 km off the main road near Namsanmukh village, and later three birds in flight were in the same spotted environs.
The White-bellied Heron Ardea insignis, Pale-capped Pigeon Columba punicea, Rufous-necked Hornbill Aceros nipalensis, and Beautiful Nuthatch Sitta formosa, all globally threatened, were seen in the neighbouring Dirak Reserved Forest, Joypur Reserve Forest and Upper Dihing (West Block) Reserve Forest by Mridupaban Phukan (pers. comm. to Kulojyoti Lahkar).
A checklist of the birds of this IBA is not available, but judging from the extant habitat, there could be 250 to 300 species, including many Restricted Range and Biome-restricted species. The area comes under Eastern Himalayas Endemic Bird Area (Stattersfield et al. 1998) and Biome-9 (Indo-Chinese Tropical Moist Forest) (BirdLife International, undated).
OTHER KEY FAUNA: There has been no detailed study on the mammalian and reptilian fauna of this site, but incidental data reveals that Asian Elephant Elephas maximus, Capped Langur Trachypithecus pileatus, Hoolock Gibbon Hylobates hoolock, Tiger Panthera tigris, Leopard P. pardus, Barking Deer Muntiacus muntjak and Sambar Cervus unicolor are known to occur.
BirdLife International (2019) Important Bird Areas factsheet: Namsangmukh - Borduria. Downloaded from http://www.birdlife.org on 16/10/2019.