Biak Leaf-warbler Phylloscopus misoriensis


Taxonomic note

Phylloscopus poliocephalus and P. makirensis (Sibley & Monroe [1990, 1993]) have been lumped and subsequently split into P. poliocephalus, P. misoriensis and P. maforensis following del Hoyo and Collar (2016).


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.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - -

Red List history
Year Category Criteria
2022 Near Threatened B1b(ii,iii); C2a(ii)
2016 Vulnerable C2a(ii)
Species attributes

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

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 3,600
Extent of Occurrence breeding/resident (km2) 3,000
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 2500-9999 poor suspected 2021
Population trend Decreasing suspected -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 5-10 - - -
Decline (10 years/3 generation past and future) 5-10 - - -
Number of subpopulations 1 - - -
Percentage in largest subpopulation 100 - - -

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.

Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Indonesia N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Forest Subtropical/Tropical Moist Lowland suitable resident
Forest Subtropical/Tropical Moist Montane major resident
Altitude 0 - 740 m Occasional altitudinal limits  

Threats & impact
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%) Slow, Significant Declines Low Impact: 5
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
Ecosystem degradation, Ecosystem conversion

Recommended citation
BirdLife International (2023) Species factsheet: Phylloscopus misoriensis. Downloaded from http://www.birdlife.org on 24/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/03/2023.