Data Zone
Justification of Red List category
This species qualifies as Critically Endangered because it appears to survive in tiny numbers at only one locality, where its habitat continues to be destroyed and degraded, such that its overall range and population are likely to be declining.
Population justification
The population is estimated to number fewer than 50 individuals and mature individuals. This estimate was derived from analyses of recent records and area of remaining habitat (BirdLife International 2001).
Trend justification
Forest loss and degradation continues within the montane forest around the Sahendaruman crater, including small gaps that have been opened up for trapping bats (R. Martin in litt. 2016), and as a result this species is suspected to be in a decline, although the likely rate of decline cannot be estimated due to the alarming paucity of recent records.
This species is restricted to Sangihe, Indonesia, where, until 1996, it was known from only a single historical specimen and was thus quite possibly already rare by the 19th century. It was seen twice in 1996 and sound-recorded once out of 148 point counts in 1999 from Gunung Sahendaruman and adjacent Sahengbalira (Riley 2002). Another single sighting was recorded amongst 499 point counts in 2009 (Burung Indonesia 2009), and a single observation of three Zosterops spp. in flight was the only potential sighting from 171 point counts and 22 days within the elevational range in 2015 (Martin 2018, R. Martin in litt. 2018). It is regarded as extremely rare and infrequently encountered in the remaining 8 km2 of appropriate habitat, and documented records since 2000 have all been in an even more restricted area along the eastern part of the ridgeline. While there has been no population estimate, it is likely that fewer than 50 mature individuals survive.
It frequents the mid-storey to upper canopy of primary broadleaved ridgetop forest, often with a high density of Pandanus spp., where it gleans insects from leaves and presumably also forages on fruit. It appears to be strictly confined to altitudes between 750 m and the highest point along the crater (c. 1,040 m).
Virtually the entire island of Sangihe has been deforested and converted to agriculture. The very small population of this species in the area of habitat remaining suggests that it is constrained by some unknown specialism or threat, potentially the requirement for large ranges in which to search for fruit, or the loss of habitat on the higher elevation Gunung Awu (which rises to over 1,300 m) following a very large eruption in 1966, leaving only a remnant population just within the natural elevation range on Sahendaruman (which only just exceeds 1,000 m). Whatever the reason, the clear indication is that it is extremely vulnerable to continuing habitat loss within the remaining forest. Small areas are continuing to be lost to individuals clearing small patches for crops and clearing gaps along the ridgeline in order to set mistnets to catch bats for food (R, Martin in litt. 2016). Government initiatives to plant exotic tree species, initially at lower altitudes, are now reportedly taking place at 700-900 m, further threatening the tiny remaining area of native forest (Sykes 2009).
Conservation and Research Actions Underway
The Gunung Sahendaruman Protection Forest encloses an area of 3,500 hectares, but forest of good condition is only found within an area of 1,300 hectares (Martin 2018). Within this, only a proportion is suitable for the species (Martin 2018). The Protection Forest is largely mixed agriculture and spice tree plantations, which does not satisfy the designated role of the area to maintain environmental services (water, land stability). Some forest is additionally protected as watershed for a hydroelectric scheme in the Kentuhang valley, though this is within the Protection Forest boundary. Since 2014, the day to day management of the Protection Forest is under the jurisdiction of the provincial government, and a Forest Management Unit was established in 2017 to undertake this duty.
Burung Indonesia have been conducting periodic monitoring of the Critically Endangered species around the Sahendaruman crater with support from Vogelbescherming (Burung Indonesia 2009, Fauzan and Bashari 2016).
An MPhil. project conducted fieldwork on Sangihe in 2015 (Martin 2018) investigated habitat associations of the critically endangered species to model the current extent of suitable habitat and evaluate the potential for habitat restoration in different locations on the island. Burung Indonesia developed a series of community-based Village Resource Management Agreements (VRMAs) at key villages around the crater during the Global Environment Fund-supported conservation project between 2002 and 2006, which successfully slowed rates of forest clearance (BirdLife Indonesia 2007). Between 1995 and 2005 the 'Action Sampiri' project worked for biodiversity conservation in Sangihe and Talaud, conducting fieldwork, establishing conservation awareness programmes (including village and school meetings, distribution of leaflets etc.) and developing ideas for future land-use through agreements between interested parties (local people, local government, forestry officials and timber companies). Sangihe is a priority site for the Critical Ecosystem Partnership Fund, and Burung Indonesia are the Regional Implementation Team for the Wallacea Hotspot. A project conducting a forest cover survey through ground-truthing remote sensed forest cover maps began in 2017, and an extension of the VRMA programme is planned.
There have been proposals to change the designation of the Protection Forest around the Sahendaruman crater to the more strictly controlled wildlife reserve; however, this is considered to have the potential to greatly deteriorate community attitudes to the site, with potentially severely damaging results (Fauzen and Bashari 2016). The Wildlife Conservation Society has also worked on the island since 2007, trying to promote sympathetic land use and development by villages surrounding the crater (N. Brickle in litt. 2010). A local resident and former bird guide is monitoring the loss of native forest for plantations of exotic tree species and trying to raise awareness of the threat this poses to the species (Sykes 2009, W. Pangimangan in litt. 2015).
12 cm. Small, arboreal, warbler-like bird. Rich olive-green upperparts with striking yellow-green rump and darker green-black tail. Black forehead, broad white eye-rings. Bright yellow chin, throat and undertail-coverts, rest of underparts pearly-white with grey flanks. Pale orange bill and legs. Voice Contact call apparently thinner and higher-pitched than Z. atrifrons. Similar spp. The related Black-fronted White-eye (Z. atrifrons) is slightly smaller, duller and has darker bare parts.
Text account compilers
Symes, A., Benstead, P., Bird, J., Taylor, J., Calvert, R., Tobias, J., Wright, L, Martin, R.
Contributors
Pangimangen, W., Martin, R., Brickle, N.
Recommended citation
BirdLife International (2024) Species factsheet: Sangihe White-eye Zosterops nehrkorni. Downloaded from
https://datazone.birdlife.org/species/factsheet/sangihe-white-eye-zosterops-nehrkorni on 24/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 24/12/2024.