This EBA includes mountains on the Indonesian island of Sumatra (in the provinces of Aceh, Sumatera Utara, Sumatera Barat, Jambi, Bengkulu, Sumatera Selatan and Lampung) and in Peninsular Malaysia. The Barisan range runs the entire length of western Sumatra, and has several peaks of over 3,000 m, the highest being Mt Kerinci at 3,805 m. These mountains were formed by uplift of sedimentary deposits, although they also include 15 or more volcanoes, of which at least nine are active (Whitten et al. 1987b, van Marle and Voous 1988). In Peninsular Malaysia, the restricted-range birds occur on the Main Range, which runs from north to south in the western part of the peninsula, and on the outlying Larat Hills, Mt Tahan and Mt Benom; these are all relatively low, reaching a maximum of 2,189 m at Mt Tahan.

The natural vegetation of Sumatra and Peninsular Malaysia is tropical rain forest, characterized by high temperatures and rainfall which vary little over the year. The restricted-range birds occur in montane forest, although many are also found in hill dipterocarp forest (see Whitmore 1984) down to c.500 m (this contour defines the lower altitudinal limit of the EBA), with a few in the alpine zone above the treeline. The transitions between these vegetation zones tend to occur at higher altitudes on Sumatra than in Peninsular Malaysia: on Sumatra, the transition between hill dipterocarp forest and lower montane forest is at c.1,000 m, and that from lower to upper montane forest is at c.2,000 m, but in Peninsular Malaysia these transitions occur at c.750 and 1,500 m respectively (and lower still on the outlying ranges) (Whitmore 1984, van Marle and Voous 1988).

The mountains of Sumatra and Peninsular Malaysia are defined as comprising a single EBA because they share more restricted-range species than are endemic to the mountains of Peninsular Malaysia alone. Of the 20 species confined to this EBA, 14 are endemic to Sumatra and two to Peninsular Malaysia, and four are shared, including the monotypic endemic genus Psilopogon. This EBA has affinities with the other Greater Sunda montane EBAs, sharing 12 restricted-range species with the Javan and Bali forests (EBA 160), and five with the Bornean mountains (EBA 157).

The mountains of Peninsular Malaysia are relatively well known ornithologically (e.g. Medway and Wells 1976, Yatim 1993), but those of Sumatra are less well studied (see van Marle and Voous 1988, Holmes 1996) and much remains to be learned about the habitat requirements and distributions of that island's restricted-range species. All are primarily forest birds, but there is some variation in their altitudinal distribution. Several species appear to be particularly associated with hill dipterocarp and lower montane forest, notably Rheinardia ocellata (restricted within this EBA to hill dipterocarp forest in Peninsular Malaysia), Treron oxyura, Carpococcyx viridis, Batrachostomus poliolophus, Pitta venusta, Pycnonotus leucogrammicus, P. tympanistrigus, P. nieuwenhuisii (considered to be a lowland-forest-slope specialist by Wells 1985), Chloropsis venusta, Garrulax lugubris, Napothera marmorata and Dicrurus sumatranus.

Several species appear to be localized in their distribution on Sumatra, including Lophura hoogerwerfi, which is known only from the northern Barisan range, and L. inornata and Carpococcyx viridis, which have only been recorded in the southern Barisan range.

Vanderbilt's Babbler Malacocincla vanderbilti, known by a single specimen from northern Sumatra was recognized as a full species by Sibley and Monroe (1990, 1993) but is judged by (Mees 1995) not to be one, and has not been included here.

The main threat to the birds of this EBA is deforestation. On Sumatra, at least a third of the natural area of montane forest on the island has been lost, and two-thirds to four-fifths of the lowland forest, and natural vegetation is probably being lost faster than in any other part of Indonesia. Agricultural encroachment by shifting cultivators is an important cause of deforestation, which is affecting large areas of hill dipterocarp and lower montane forest, even within gazetted protected areas (Whitten et al. 1987b, Collins et al. 1991, A. J. Whitten in litt. 1993; see Thorsell 1985). In Peninsular Malaysia, the montane forests remain relatively intact, although some logging of lower montane forest and the development of three hill stations has led to localized deforestation, but plans for a road linking these hill stations would pose severe environmental problems if implemented (Collins et al. 1991, Kiew 1994, McGowan and Garson 1995).

Seven of the restricted-range birds of this EBA are classified as threatened, including those species which are believed to be most vulnerable to habitat destruction because they have particularly small ranges or are confined to a narrow (and relatively low) altitudinal band. Carpococcyx viridis was classified as Vulnerable by Collar et al. (1994), who treated it as conspecific with C. radiatus, but needs to be re-evaluated (to ascertain whether it qualifies for a higher threatened category) now that it has been given full specific status. Three particularly poorly known species are listed as Data Deficient. Nineteen more widespread threatened species occur on Sumatra and in Peninsular Malaysia, but these are all birds of lowland forest or wetlands which are mainly found outside the EBA, although several of them overlap in distribution with the restricted-range species in hill dipterocarp forest.

There are over 20 protected areas in the Barisan range on Sumatra, and several in the mountains of Peninsular Malaysia, which cover well over 10% of the area of the EBA. Many of these contain large areas of montane and hill dipterocarp forest, and they are spread throughout the entire extent of the EBA and probably include populations of all of the restricted-range species. Important protected areas with large areas of montane forest include Taman Negara National Park (which includes Mt Tahan) and Cameron Highlands Wildlife Sanctuary in Peninsular Malaysia, and Gunung Leuser, Kerinci Seblat and Bukit Barisan Selatan National Parks on Sumatra.

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Sumatra and Peninsular Malaysia. Downloaded from https://datazone.birdlife.org/eba/factsheet/158 on 22/11/2024.