||Mauritius Olive White-eye
||Oiseau-lunettes de l'Ile Maurice
Zosterops chloronothos chloronothos Collar et al. (1994)
Zosterops chloronothos chloronothos Sibley and Monroe (1990, 1993)
Zosterops chloronothos chloronothos BirdLife International (2000)
||10 cm. Small, drab, warbler-like bird of forest. Dull olive-green above with paler underparts, tending towards cream on belly and yellow on vent. Similar spp. Confused only with Mauritius Grey White-eye Z. borbonicus mauritianus from which it differs by having dark, not grey rump, noticeable white eye-ring, and being overall olive, not grey. Also has longer, fine, decurved bill. Voice Metallic plik plik contact note and warbled song. Hints Not easy to find in the Black River Gorge area in south-west Mauritius.
|Red List Category & Criteria:
||Taylor, J. & Butchart, S.
||Cole, R., Jones, C., Nichols, R., Safford, R., Switzer, R. & Tatayah, V.
||Benstead, P., Bird, J., Calvert, R., Ekstrom, J., McClellan, R., Shutes, S., Symes, A., Warren, B.
This species is listed as Critically Endangered because it is estimated to have an extremely small population which is declining owing to predation by introduced mammals. In addition, it has a very small range, and its habitat is declining in quality and extent.
|Previously published Red List assessments:|
- 2009 – Critically Endangered (CR)
- 2008 – Critically Endangered (CR)
- 2004 – Critically Endangered (CR)
- 2000 – Endangered (EN)
- 1996 – Critically Endangered (CR)
- 1994 – Critically Endangered (CR)
- 1988 – Threatened (T)
|Range Description:||Zosterops chloronothus is endemic to Mauritius. It declined rapidly from 350 pairs in the mid-1970s, to c.275 pairs by the mid-1980s. Intensive fieldwork during 1990-1993 indicated a further reduction to an estimated 200 pairs (Safford 1997c), and fieldwork between 1998 and 2001 concluded that the global population size lay within the range 93-148 pairs (R. Switzer in litt. 2003, Nichols et al. 2004, Anon 2006) within an area of less than 25 km2 located in the southwest of the Black River Gorges National Park. It is widespread in upland native forest, but largely absent from the whole Macchabé-Brise Fer area and Fouge Range (Safford 1997c). The species's core distribution has contracted since 1975 - it has disappeared from three outlying sites (Tamarin Falls, Jouanis and Monvert) and the core area has decreased by 50% (Nichols et al. 2005). Its status in central Mauritius (Montagne Lagrave and the central plateau relics) remains uncertain (R. Switzer in litt. 2003, Nichols et al. 2004), although one was seen on Mt Lagrave in the breeding season in 2011/2012 (V. Tatayah in litt. 2012). Highest densities are between Montagne Cocotte and Combo Forest with up to 10 pairs/km2 (C. Jones in litt. 2000). Birds exploit isolated habitats over a wide area of the central plateau, including many relict patches of native vegetation (Safford 1997c). Following twenty years of conservation work on Ile aux Aigrettes, 16 white-eyes were released on the predator free island between December 2006 and March 2007 (Anon 2006). A further release of around 20 birds in December 2007 aimed to further the establishment of a small sub-population on Ile aux Aigrettes, and birds have since successfully fledged young there in the 2007/08, 2008/09 and 2010/11 seasons (nine pairs and a total of six fledged young) (Anon. 2011). In March 2011 the population on Ile aux Aigrettes stood at 25 (Anon. 2011), with 26 individuals in March 2012 (V. Tatayah in litt. 2012).|
|♦ Estimated area of occupancy (AOO) - km2:||32||♦ Continuing decline in area of occupancy (AOO):||Yes|
|♦ Extreme fluctuations in area of occupancy (AOO):||No||♦ Estimated extent of occurrence (EOO) - km2:||61|
|♦ Continuing decline in extent of occurrence (EOO):||Yes||♦ Extreme fluctuations in extent of occurrence (EOO):||No|
|♦ Number of Locations:||8||♦ Continuing decline in number of locations:||Yes|
|♦ Extreme fluctuations in the number of locations:||No||♦ Lower elevation limit (metres):||200|
|♦ Upper elevation limit (metres):||600|
|Range Map:||Click here to open the map viewer and explore range.|
Conservation Actions Underway
The species has long been protected by law. The Black River National Park partly covers the species's distribution. Habitat around Bassin Blanc may be bought by compulsory purchase in the future (Jones and Hartley 1995, R. Safford in litt. 1999). A species recovery programme was initiated by the Mauritian Wildlife Foundation in September 2005, in which territories identified in the most recent survey were revisited and the breeding behaviour of these birds was closely monitored (R. Cole in litt. 2007). Between 2005-2008 an intensive management plan was applied, involving wild population monitoring, predator control at nest sites, rescue/harvest of wild nests, artificial incubation and hand-rearing of offspring, and a trial release of birds to the predator-free, restored offshore islet Ile aux Aigrettes in December 2006 (R. Cole in litt. 2007). The aims of this programme are to increase knowledge of the species and its current threats, and investigate management techniques with a view to designing a long-term management strategy (R. Cole in litt. 2007). Rehabilitation of native vegetation in small plots has been initiated through exclusion of exotic plants and animals, and there is ongoing research to assess benefits to native birds (Safford and Jones 1998). A total of 38 individuals, all originating from wild nests, were released onto Ile aux Aigrettes between 2006 and 2008 (R. Cole in litt. 2007, G. Maggs in litt. 2010). The Ile aux Aigrettes sub-population is closely monitored and provided with supplementary food, and the first fledglings were produced in 2008 (G. Maggs in litt. 2010). In 2010, 14 fledglings were produced from five breeding pairs, and the total population currently stands at 25 individuals (G. Maggs in litt. 2010). Several individuals from rescued nests were hand-reared by a team from Chester Zoo, the Durrell Wildlife Conservation Trust and the Mauritian Wildlife Foundation (Sørensen 2005), but it is now thought that releases to predator-free islets and effective management of upland habitat are more viable options for conserving the Mauritius Olive White-eye (R. Cole in litt. 2007). Releases and nest rescues are now set to cease, and intensive research regarding habitat use, feeding ecology and nesting success will be carried out to highlight major limiting factors for the species and refine management techniques (G. Maggs in litt. 2010). Conservation Actions Proposed
Continue population monitoring and ringing. Continue rehabilitation of native forest in appropriate areas to improve food sources for the species. Continue monitoring of accessible nests at Combo and Ile aux Aigrettes (Anon 2011). Develop Conservation Management Areas (CMAs) within the species's current range which have high densities of important nectar-producing plants and where predators are strictly controlled (Nichols et al. 2005). Initiate studies to investigate habitat requirements with view to developing habitat enrichment programmes and future species management techniques. Continue to search the Black River National Park and other suspected areas in Mauritius to identify new sub-populations (Anon 2011). Continue and extend the use of poison grids around nest sites to reduce rat predation (Anon 2011).