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

Taxonomic note

Zosterops poliogastrus, Z. kaffensis, Z. kulalensis, Z. kikuyuensis, Z. silvanus, Z. eurycricotus, Z. mbuluensis and Z. winifredae (del Hoyo and Collar 2016) were previously lumped as Z. poliogastrus following Dowsett & Forbes-Watson (1993) and Sibley & Monroe (1990, 1993).

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	C2a(i)

Red List history

Year	Category	Criteria
2022	Vulnerable	C2a(i)
2016	Endangered	B1ab(i,ii,iii,v)
2012	Not Recognised
2008	Not Recognised
2006	Not Recognised
2004	Endangered
2000	Endangered
1994	Critically Endangered
1988	Not Recognised

Migratory status	not a migrant	Forest dependency	medium
Land-mass type	continent	Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	870 km2	medium
Area of Occupancy (breeding/resident)	116 km2
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	1200-9000,1830-4700 mature individuals	poor	estimated	1999
Population trend	decreasing	-	inferred	-
Generation length	2.6 years	-	-	-
Number of subpopulations	3-10,3	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: Surveys in the late 1990s estimated a population of 7,123 (3,770-13,594) total individuals (Mulwa et al. 2007). This would roughly equate to 4,750 (2,500-9,100) mature individuals.

The species occurs in two of the three main blocks in the Taita Hills (the Dawida complex comprising eight occupied fragments and the Mbololo massif; no evidence of the species was found from the Sagala massif) and also on Mount Kasigau c. 50 km southeast (Mulwa et al. 2007). Mulwa et al. (2007) estimated numbers from within each block from fieldwork undertaken between November 1998 and September 1999; Dawida complex 878 individuals (95% confidence interval: 461-1,779), Mbololo 651 individuals (352-1,188) and Kasigau 5,594 individuals (2,957-10,627). These three areas are considered to represent three separate subpopulations, although there is the possibility that there may be further subdivision within the Dawida block.

Notably there is concern that the Kasigau population has since crashed (M. Adamjee in litt. 2022). The estimate was made at a time when the habitat was 'pristine' and the abundance of this species was exceptional, but the apparently insular nature of this population suggested fragility (Mulwa et al. 2007, R. Mulwa in litt. 2022). Subsequently the habitat has become at least partly degraded and in numerous recent visits abundance of Taita White-eye has been far lower, and a value of 1,000-1,500 individuals is considered a more accurate current range (M. Adamjee in litt. 2022). This revised value would suggest that no subpopulation is likely to hold more than 1,000 mature individuals, as well as indicating that at one site a rapid reduction is reported to have occurred. With degradation of the preferred montane forest habitat noted to be ongoing (Wakesa et al. 2020, R. Mulwa in litt. 2022) along with the noted reduction in abundance of the largest subpopulation, it is inferred that there is an ongoing decline in the number of mature individuals.

Trend justification: The population is inferred to be declining as a result of ongoing forest loss. Data from Global Forest Watch (2020) suggest that between 2009 and 2019, 1.2% of the forest in the species' range was lost. However, analysis by Wakesa et al. (2020) found that between 1973 and 2016, the larger forest blocks in the Taita Hills (Chawia, Fururu, Mbololo, Ngangao and Vuria) decreased by 23.2%. This roughly equates to a rate of 6% over 10 years. The direct rate of population decline is difficult to quantify as this species prefers edge habitats, however due to the restrictedness of the remaining habitat, the overall trend is declining.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Kenya	extant	native	yes

Country/Territory	IBA Name
Kenya	Taita Hills Forests

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	840 - 1725 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Causing/Could cause fluctuations		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Taita White-eye Zosterops silvanus. Downloaded from https://datazone.birdlife.org/species/factsheet/taita-white-eye-zosterops-silvanus on 23/12/2024.
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 23/12/2024.