• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
This species is classified as Vulnerable since it has a very small range, confined to the top of an active volcano. The population is suspected to have declined since 1985 owing to a reduction in the Area of Occupancy as a result of volcanic activity, however the extent of habitat is expected to recover through natural regeneration so the species is not suspected to be undergoing a continuing decline. Nevertheless, the limited range and small population of this species render it extremely susceptible to future threats, most notably, a serious eruption. In such a case the species may warrant uplisting to Critically Endangered.

Population justification
The range estimate of 2,500-9,999 individuals is supported by recent surveys that estimated densities of 1,500 birds/km², suggesting the population size is towards the high end of this range (C. Marsh in litt. 2007). This estimate equates to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.

Trend justification
Surveys in 2005 indicated that densities had remained stable since 1985 (C. Marsh in litt. 2007). However, the population is suspected to have declined at an unknown rate since 1985 owing to a reduction in the extent of habitat as a result of volcanic activity. The extent of habitat is expected to recover through natural regeneration (C. Marsh in litt. 2007).

Zosterops mouroniensis is restricted to, although common in, the upper reaches of the actively volcanic Mt Karthala, Grand Comoro (= Ngazidja), Comoro Islands. In 1988, the population was estimated to be a few thousand birds at most (Louette et al. 1988). Surveys in 2005 indicated that densities had remained stable since 1985 (C. Marsh in litt. 2007). However, the population is suspected to have declined since 1985 owing to a reduction in the extent of habitat as a result of volcanic activity. The extent of habitat is expected to recover through natural regeneration (C. Marsh in litt. 2007, 2009).

It is confined to a single small area of Philippia heath woodland around the crater of Mt Karthala. During surveys in 2005 is was recorded at 1,870-2,180 m, with a few individuals encroaching into the upper limits of the forest (C. Marsh in litt. 2007). It can be seen in large groups foraging in bushes or flying just over vegetation, and has been observed in mixed species groups, including with Z. maderaspatanus (Louette et al. 1988, C. Marsh in litt. 2007, Safford 2013). It is a fruit- and insect-eating bird. One nest has been found 4 m above the ground, 1 m from the top of a Philippia bush (Safford 2013).

Large patches of heath near the summit of Mt Karthala were burnt in 1958, probably as a result of volcanic activity (Benson 1960). Following eruptions in 2005, a reduction in the area of Philippia habitat was observed, particularly within and just around the crater above 2,500 m (C. Marsh in litt. 2007). A future eruption could be catastrophic for the species. Tree-heath is threatened by browsing cattle and by fire used to stimulate growth of palatable shoots (Safford 2001). In 2005, cattle grazing was judged to be limited in extent (C. Marsh in litt. 2007). With this island's large, increasing human population (Louette et al. 1988), clearance of forest for agriculture is occurring on all but the poorest soils. Since 1983, intact forest may have declined by over 25% as agriculture has advanced steadily up the slopes of Mt Karthala towards the habitat of this species. Secondary forest in the agricultural belt is dominated by exotic plants, particularly strawberry guava Psidium cattleianum, which could spread into and degrade remaining native forest. If plans to build a road to Mt Karthala's crater are resurrected, exploitation and fragmentation of the forest, and the spread of exotic species, could be accelerated (Safford 2001). Introduced rats may act as nest predators or food competitors (Safford 2001). The lower boundary of Philippia, and thus the species's range, may be pushed upwards by an expansion of the forest owing to a future rise in global temperatures (C. Marsh in litt. 2007).

Conservation Actions Underway
A protected area (national park, biosphere reserve or resource management area) on Mt Karthala has been proposed, but has not yet materialised (Louette and Stevens 1992, Safford 2001, Safford 2013).

Conservation Actions Proposed
Carry out surveys to monitor population trends. Monitor rates of habitat clearance and degradation. Research the ecology of this species to aid conservation plans. Create a protected area on Mt Karthala to encompass the known range of this species, and develop a management strategy (Louette and Stevens 1992, Safford 2001). Develop an environmental education programme on the island (Louette and Stevens 1992). Encourage locally-organised ecotourism as an alternative source of income for inhabitants of the Mt Karthala area (Safford 2001).

13 cm. Medium-sized, warbler-like bird. Dull olive-brown upperparts with narrow white eye-ring. Yellowish-green underparts, brighter on throat and vent. Similar spp. Madagascar White-eye Z. maderaspatanus much brighter yellow below and greener above, but range rarely overlaps. Voice Noisy, with continual contact by typical buzzy white-eye calls and twitterings. Hints Gregarious, restless.

Text account compilers
Benstead, P., Ekstrom, J., Pilgrim, J., Shutes, S., Symes, A., Taylor, J., Warren, B. & Westrip, J.

Contributors
Marsh, C.

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Recommended citation
BirdLife International (2024) Species factsheet: Mount Karthala White-eye Zosterops mouroniensis. Downloaded from https://datazone.birdlife.org/species/factsheet/mount-karthala-white-eye-zosterops-mouroniensis on 26/12/2024.
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 26/12/2024.