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).
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
Red List history
IUCN Red List criteria met and history
||not a migrant
Land-mass type - continent
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.
Important Bird and Biodiversity Areas (IBA)
BirdLife International (2023) Species factsheet: Zosterops silvanus. Downloaded from
http://datazone.birdlife.org/species/factsheet/taita-white-eye-zosterops-silvanus on 04/10/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from
http://datazone.birdlife.org on 04/10/2023.