The Lesser Sunda island of Sumba, like the Northern Nusa Tenggara EBA (EBA 162), is in Nusa Tenggara Timur province of Indonesia. It is a hilly island, with deeply dissected plateaus, but there is little land above 1,000 m and the highest peak only reaches 1,225 m. Sumba has a seasonal climate because it lies in the rain-shadow of the Australian continent and receives little rain in the south-east monsoon between April and November.

The major natural vegetation type is deciduous monsoon forest, but there are pockets of tropical semi-evergreen rain forest where the south-facing sides of the hills receive moderately high rainfall from onshore winds, some evergreen gallery forest in wet depressions and gullies, and montane forest above c.800 m (FAO 1982c, Whitmore 1984). Much of the island is now covered in dry grassland and savanna woodland as a result of forest clearance and the practice of burning in the dry season (FAO 1982c).

Turnix everetti is found in open grassland, but otherwise the restricted-range species are all birds of forest or woodland. Recent ornithological survey work on Sumba by Jones et al. (1995a) has greatly improved knowledge of the habitat requirements and conservation status of these species. Most of them were found in all forest types, in both primary and secondary forest, and were estimated to have large populations on the island. The exceptions are Ptilinopus dohertyi (a Sumba endemic) and Zoothera dohertyi, which are associated with primary forest in the higher parts of the island, and Aceros everetti (a Sumba endemic), which prefers primary and mature secondary semi-evergreen rain forest in the lowlands. Two further Sumba endemics, Turnix everetti and Ninox rudolfi, were not recorded frequently enough during the survey work to permit a full assessment of their habitat requirements and conservation status.

Two taxa which are confined to this EBA, Sumba Brown Flycatcher Muscicapa segregata and Sumba Myzomela Myzomela dammermani were treated as full species by Sibley and Monroe (1990, 1993) but are considered in this study to be forms of the more widespread Asian Brown Flycatcher M. dauurica and Red-headed Myzomela M. erythrocephala respectively, following Andrew (1992).

The area of forest on Sumba has declined significantly during the twentieth century, mainly through the clearance and repeated burning of vegetation to provide land for grazing and cultivation and because of unsustainable levels of utilization of fuelwood and other minor forest products. Closed-canopy forest now covers c.10% of the island and is mainly confined to relatively small and isolated pockets, although some more extensive areas remain along the south coast. Sumba has no logging industry, but some trees are removed for local use (Jones et al. 1995a, Jepson et al. 1996).

Four of Sumba's endemic restricted-range birds are classified as threatened: Ptilinopus dohertyi and Aceros everetti because their populations are each estimated to be below 10,000 individuals and their specialized habitat requirements make them vulnerable to further deforestation, and Turnix everetti and Ninox rudolfi because they appear to be scarce and they may also be vulnerable to loss of their habitat. However, the ecology of T. everetti remains very poorly understood, and this species may actually have benefited from the replacement of forest by open grassland.

A more widespread threatened species (found throughout much of Wallacea), Yellow-crested Cockatoo Cacatua sulphurea (classified as Endangered), is represented on Sumba by the endemic subspecies citrinocristata (which perhaps warrants full specific status: D. A. Holmes in litt. 1993); it is declining throughout its range because of a combination of habitat loss and unsustainable levels of trapping for the bird trade.

The only gazetted protected area on Sumba is Langgaliru Nature Reserve. The PHPA/BirdLife International Sumba Forest Conservation Project has proposed the gazetting of a network of seven key forest sites which include the largest remaining areas of forest on the island and would adequately cover all of the important habitats of the EBA: top priority are Wanggameti-Tabundung and Langgaliru-Manupeu (an extension to the existing protected area, to include the largest single population of Aceros everetti); high priority are Luku Melolo, Yawila and Poronumbu; and important additional areas are Lulundilu and Tanjung Ngunju (Jepson et al. 1996).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Sumba. Downloaded from https://datazone.birdlife.org/eba/factsheet/163 on 22/11/2024.