Data Zone
Justification of Red List category
This species is restricted to the twin islands of Biak-Supiori but despite the very small distribution the population size is not suspected to approach thresholds for listing as threatened under Criterion C. The population is suspected to be declining due to an ongoing slow rate of forest cover loss. The extent of occurrence, only 3,600 km2, indicates that the species may be at risk, although the population is not severely fragmented and there are parts of the range where the main threat is not believed to apply. Forest loss is ongoing however, hence a continuing decline in the area, extent or quality of habitat is estimated. In conjunction with the very small extent of occurrence, the species is considered to approach the thresholds for listing as threatened, meeting Criterion B1b(iii) but not a second subcriterion. Accordingly, Biak White-eye is assessed as Near Threatened.
Population justification
This is a poorly known species and no population estimates are available. It is described as 'uncommon' by Beehler and Pratt (2016) but appears to be widespread and readily observed in small flocks (eBird 2022). The population size is not thought to be below 10,000 mature individuals (the threshold for listing as Threatened under Criterion C).
Trend justification
No direct assessment of rate of population change has been made for the species. It is considered to be relatively forest dependent (although it is somewhat tolerant of degraded habitat) and there has been a slow rate of forest cover loss, up to 4% in the ten years to 2022 (data from Global Forest Watch 2022, using Hansen et al. [2013] data and methods disclosed therein) and this is suspected to be causing broadly equivalent reductions in population size of this species. These rates are suspected to occur in the future. An accelerated rate of decline is considered unlikely given the impenetrability of Supiori's forests.
This species is endemic to the twin-islands of Biak-Supiori in Geelvink Bay, West Papua, Indonesia.
This species occurs in forest up to 675 m, including forest edge, secondary forest, and even low secondary growth (Beehler and Pratt 2016).
Forest on Biak has come under heavy pressure from logging and subsistence farming, though large-scale logging has not been economically feasible for some time (Wikramanayake et al. 2002). The rate of forest cover loss recorded through satellite monitoring has been slow in the past two decades, and in the three generations to 2022, the maximum rate is estimated at 4.0% (Global Forest Watch 2022, using Hansen et al. [2013] data and methods disclosed therein). Much of Supiori comprises virtually impenetrable, forested limestone mountains, which are likely to be safe from habitat degradation.
Conservation Actions Underway
The species is assumed to be present in the 110 km2 Biak-Utara protected area and throughout the 420 km2 Pulau Supiori Nature Reserve (UNEP-WCMC 2021a,b), both of which comprise virtually impenetrable limestone areas (Wikramanayake et al. 2002).
Conservation Actions Proposed
Conduct surveys on both islands to establish its current distribution, population status and assess its habitat requirements. Afford formal protection to further key sites where appropriate.
Text account compilers
Berryman, A.
Contributors
Mahood, S., Benstead, P., Khwaja, N. & Gilroy, J.
Recommended citation
BirdLife International (2024) Species factsheet: Biak White-eye Zosterops mysorensis. Downloaded from
https://datazone.birdlife.org/species/factsheet/biak-white-eye-zosterops-mysorensis on 22/11/2024.
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 22/11/2024.