This EBA includes the plains and foothills of the Brahmaputra watershed in the north-east of the Indian subcontinent. It is centred around the Indian state of Assam, and includes the lowlands of extreme eastern Nepal (at least formerly), the Indian states of Sikkim, northern West Bengal, Arunachal Pradesh, Nagaland, Manipur and Meghalaya, the Bangladeshi divisions of Rajshahi and Chittagong, presumably southern Bhutan, and possibly the extreme west of Myanmar.

The original vegetation of the plains was seasonally inundated floodplain forest and grassland, with an adjacent strip of undulating land ('terai') at the base of the foothills; this land was often marshy and supported tall elephant grass and forest. Most of the plains and foothills are now, however, converted to agricultural land (Gaston 1984, Ali and Ripley 1987), and the restricted-range birds are associated with the remaining grassland and wetland habitats, mainly at altitudes below 1,000 m.

This EBA is virtually enclosed by the mountains of the Eastern Himalayas EBA (130), and there is a slight overlap in the altitudinal ranges of the birds from the two. However, the species of that EBA breed in forest rather than in open habitats, and generally at higher altitudes, although many are altitudinal migrants which move down to forest in the foothills outside the breeding season.

The restricted-range birds are found in a variety of grassland, scrub and wetland habitats on the plains, often along rivers, and in the foothills. However, Perdicula manipurensis is confined to the foothills, and has a stronghold in the Manipur basin, where neither of the other species has been recorded. Paradoxornis flavirostris sometimes ranges to well above 1,000 m, but is much scarcer in the hills than the plains (Ali and Ripley 1987). Pellorneum palustre has not been recorded in the north-western section of the EBA, to the east of the Miri hills. There has been relatively little recent ornithological activity in this region, and there are few recent records of any of the three species.

The principal threat to this EBA is the continuing conversion of natural grassland and wetland to agricultural and urban land-uses, together with agricultural intensification and industrialization. These habitats are now much reduced in area and fragmented (see Majumdar and Brahmachari 1988, Rahmani 1988, Scott 1989).

All three restricted-range species are listed as threatened because of this loss of habitat and the paucity of recent records. A considerable number of more widespread threatened species occur, or formerly occurred, in the grasslands and wetlands of this EBA. Some of these are confined to the northern Indian subcontinent and Myanmar: White-bellied Heron Ardea insignis (classified as Endangered), Pink-headed Duck Rhodonessa caryophyllacea (Critical, but probably already extinct), Swamp Francolin Francolinus gularis (Vulnerable), Jerdon's Babbler Chrysomma altirostre (Vulnerable), Rufous-vented Prinia Prinia burnesii (Vulnerable) and Yellow Weaver Ploceus megarhynchus (Vulnerable). Others range elsewhere: Spot-billed Pelican Pelecanus philippensis (Vulnerable), Lesser Adjutant Leptoptilos javanicus (Vulnerable), Greater Adjutant L. dubius (Endangered), White-winged Duck Cairina scutulata (Endangered), Pallas's Sea-eagle Haliaeetus leucoryphus (Vulnerable), Masked Finfoot Heliopais personata (Vulnerable), Bengal Florican Houbaropsis bengalensis (Endangered) and Bristled Grass-warbler Chaetornis striatus (Vulnerable).

There are over 30 protected areas in or near this EBA, including such large and important ones as Kaziranga National Park. They are spread throughout the area, but there is little published information to indicate which of them supports populations of the restricted-range (and other threatened) species or includes areas of habitat suitable for them. There has been extensive encroachment into protected areas in this part of India by people displaced by floods, erosion or inter-ethnic conflict; this is affecting grassland habitats, and wetland quality is deteriorating rapidly due to siltation and eutrophication; and in the protected areas management practices are oriented solely towards large mammals (Bhattacharjee 1995). There is therefore a need to investigate which of the established protected areas support the restricted-range birds, and to determine whether the current protected-area system is adequate and whether management practices are appropriate.

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Assam plains. Downloaded from https://datazone.birdlife.org/eba/factsheet/130 on 22/11/2024.