Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population size has not been quantified, though national population estimates include: < c.50 individuals on migration in Korea;c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Japan and c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Russia (Brazil 2009).
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.
Text account compilers
Ekstrom, J., Butchart, S., Harding, M.
BirdLife International (2022) Species factsheet: Phylloscopus borealoides. Downloaded from http://www.birdlife.org on 02/12/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/12/2022.