This EBA follows the Himalayan range east from the Arun-Kosi valley of eastern Nepal, through Bhutan, north-east India (Sikkim, northern West Bengal and Arunachal Pradesh), south-east Tibet autonomous region and north-east Myanmar to south-west China (north-west Yunnan province). It also includes the mountain ranges to the south of the Brahmaputra river, which extend through north-east India (Nagaland, Manipur, southern Assam, Meghalaya and Mizoram) to the Chin hills in western Myanmar, and the Chittagong hills in south-east Bangladesh.

As they lie further to the south, the mountains of this region have a distinctly different climate (and hence vegetation) from the rest of the Himalayas: they experience warmer mean temperatures and fewer days with frost, and generally have a much higher rainfall (Ramdas 1974). Two evergreen forest types appear to be particularly important breeding habitats for the EBA's restricted-range birds, both of which reach their western limit in eastern Nepal: subtropical wet hill forest is found at altitudes between approximately 1,000 and 2,000 m, and wet temperate forest at altitudes of about 1,800-3,000 m. Some species also breed in moist temperate or subalpine forests, and many are altitudinal migrants, moving outside the breeding season into tropical lowland evergreen and semi-evergreen rain forest below 1,000 m (see Champion and Seth 1968, Mani 1974, Whitmore 1984).

Knowledge of the distribution of the restricted-range species is incomplete in many parts of the EBA, so the tentative boundary adopted has been based on the documented records of these birds and their known altitudinal ranges. There are minor geographical overlaps between this EBA and the Central Himalayas (EBA 129) in eastern Nepal, and the Yunnan mountains (EBA 139) in western Yunnan and northern Myanmar. The Assam plains (EBA 131) is in the adjacent lowlands and foothills, and there is some altitudinal overlap with this EBA, but the restricted-range species of the Assam plains are confined to non-forest habitats.

This part of the Himalayas is particularly rich in restricted-range birds, and the genus Sphenocichla is endemic to the EBA. For logistical and political reasons, these mountains have always been difficult of access for ornithologists, and there are many gaps in the knowledge of habitat requirements and distributions of these birds. Many of them are altitudinal migrants, and much of the ornithological work in the EBA has taken place outside the breeding season, so it is difficult from the available information to determine the exact breeding habitat requirements and altitudinal ranges of the species. It is clear, however, that subtropical wet hill forest and wet temperate forest are particularly important breeding habitats, and that tropical lowland evergreen and semi-evergreen rain forest is used by many of the species outside the breeding season. Important recent information on the EBA's restricted-range species is included in Peng Yan-zhang et al. (1980), Inskipp and Inskipp (1991, 1993a,b), Ripley et al. (1991), Clements (1992), Katti et al. (1992), Singh (1995) and Ali et al. (1996).

The Himalayan mountains in the northern part of the EBA (first four columns in the 'Distribution patterns' table) have an avifauna distinctly different from the mountain ranges in the south (next four columns); eight or nine of the restricted-range species are only known (in this EBA) from the north and four only from the south. These two regions are combined into a single EBA because of the 9-10 species common to both. Several species have particularly small ranges: Spelaeornis badeigularis and Stachyris oglei are known only from the Lohit and Tirap Frontier Divisions of eastern Arunachal Pradesh, S. badeigularis from just a single specimen; Spelaeornis longicaudatus is restricted to the hills of Meghalaya, southern Assam and western Manipur; Apus acuticauda is only known to breed in the Khasi hills in Meghalaya and the Blue mountains in Mizoram, but up to eight individuals were seen around cliffs in south-east Bhutan in May 1996 (B. King in litt. 1996); Sitta victoriae is only known from the southern Chin hills, where it was recorded in the summit area of Mt Victoria and near Mindat (22 km to the north-west of Mt Victoria) in 1995 (Robson 1995; see Harrap and Quinn 1996).

The principal threat facing the EBA is deforestation and forest degradation. Logging, both legal and illegal, is leading rapidly to the clearance of large areas of forest in north-east India, particularly affecting the tropical lowland forests, and is even taking place within some protected areas. In the subtropical and temperate forests in the mountains, shifting agriculture and livestock-grazing have cleared and degraded the forests in many areas. Shifting agriculture can be sustainable if practised on a small scale using clearing cycles of 15-20 years, but in many areas increased population pressure has led to a rapid reduction in this cycle-for example in Meghalaya, where this has resulted in the loss of large areas of forest and severe soil erosion (Champion 1936, Collins et al. 1991, Katti et al. 1992, Ma Shi-lai et al. 1995). In eastern Nepal, the proposed Arun III hydroelectric project threatens to flood one of the best remaining areas of forest in this part of the EBA (Poole 1994, T. P. and C. Inskipp in litt. 1993).

Eleven of the restricted-range species are considered to be threatened, a greater number than in any other EBA of this region. They include the species with very small ranges described above, which are particularly vulnerable to habitat loss, and several species which appear to occur at low densities, some of which (e.g. Tragopan blythii, Lophophorus sclateri) are subject to hunting pressure (McGowan and Garson 1995). The threatened Grey-sided Thrush Turdus feae, a restricted-range species which breeds in the Shanxi mountains (EBA 136), is a non-breeding visitor to the southern part of the Eastern Himalayas (Nagaland, Manipur, Khasi and Chin hills). More widespread threatened species which occur within the EBA include Hume's Pheasant Syrmaticus humiae, Wood Snipe Gallinago nemoricola, Blyth's Kingfisher Alcedo hercules, Rufous-necked Hornbill Aceros nipalensis and Beautiful Nuthatch Sitta formosa (all classified as Vulnerable).

The EBA contains about 30 protected areas which include areas of suitable habitat for the restricted-range birds (Li Wenhua and Zhao Xian-jing 1989, IUCN 1990, 1993). They are spread through most parts of the EBA, although there are none in the Chin hills in Myanmar and there are only a few relatively small reserves in Nagaland, Manipur, Cachar and the Khasi hills. Namdapha National Park is particularly important because it contains large areas of the EBA's key habitats and supports populations of many of the restricted-range species, including at least one of the two species which are known only from eastern Arunachal Pradesh (Ripley et al. 1991). Other large protected areas include Mehao and Pakhui Sanctuaries and Blue Mountain National Park in India, Black Mountain and Royal Manas National Parks in Bhutan, and the Makalu-Barun National Park (which now includes the Apsuwa river area: J. Bland in litt. 1997; see Tymstra 1993) in Nepal.

A proposed protected area which fills an important gap in coverage of the EBA is Natma Taung (Mt Victoria) in the Chin hills, a locality for Sitta victoriae. There is also a need for increased protected-area coverage in the Nagaland, Manipur, Cachar and Khasi hills, and a proposed reserve in the Barail range is likely to be important for the restricted-range species.

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Eastern Himalayas. Downloaded from https://datazone.birdlife.org/eba/factsheet/129 on 22/11/2024.