Biak Leaf-warbler Phylloscopus misoriensis


Justification of Red List Category
This species is suspected to have a small population (comprising a single subpopulation) that is declining and also has a small range, confined to the island of Biak. It is therefore listed as Near Threatened.

Population justification
The species has been described as uncommon and possibly an order of magnitude lower than congeners (G. Dutson in litt. 2016); for example, two three-day visits to the island's forests in 2019 recorded the species only once (J. Bergmark in litt. 2021), and eBird (2021) data indicate that it is among the hardest of the island's endemics to see. Therefore, based on descriptions of abundance, population density estimates of congeners, and assuming only a proportion of habitat is occupied, the population size may fall below 10,000 mature individuals, and so is provisionally suspected to number 2,500-9,999 mature individuals until more robust, species-specific data are available. Given descriptions of this species' rarity, generating a robust population estimate should be considered a research priority.

Trend justification
Global Forest Watch (2021), using data from Hansen et al. (2013) and methods disclosed therein, indicate that between 2010 and 2020 this species lost 6-8% of forest cover (>30% canopy cover) in its range. As a forest dependent species, it is suspected to have declined at a similar rate. Forest loss in 2016-2020 occurred at the same rate, such that these declines are expected to continue in the future.

Distribution and population

Phylloscopus misoriensis is only found on the island of Biak, in Geelvink Bay, Indonesia.


This species inhabits primary and secondary forest at all elevations of Biak (Pratt and Beehler 2015, J. Bergmark in litt. 2021).


The principal threat to this species is ongoing forest clearance (Bishop 1982, Hansen et al. 2013, Global Forest Watch 2021).

Conservation actions

Conservation Actions Underway
This species occurs in the Biak-Utara protected area.

Conservation Actions Proposed
Conduct regular surveys to monitor populations. In particular, conduct surveys to calculate densities and an accurate global population size. Use remote sensing data to monitor habitat trends. Effectively protect the the Biak-Utara protected area.


Text account compilers
Berryman, A.

Bergmark, J., Butchart, S., Dutson, G., Ekstrom, J. & Westrip, J.R.S.

Recommended citation
BirdLife International (2023) Species factsheet: Phylloscopus misoriensis. Downloaded from http://www.birdlife.org on 01/04/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 01/04/2023.