Justification of Red List Category
This species has an extremely 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 is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds 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 is unknown given recent taxonomic splits. No population information is available for the nominate race, however the oshiroi and toyoshimai races are thought to be rare (del Hoyo et al. 2015).
The population trend is difficult to determine because of uncertainty over the impacts of habitat modification on population sizes.
On the Ogasawara (Bonin) Islands, Japan, intraspecific competition and human disturbance are thought to be factors contributing to low breeding productivity (Chiba and Suzuki 2011).
Text account compilers
Calvert, R., Khwaja, N., Taylor, J., Symes, A. & Ashpole, J
BirdLife International (2020) Species factsheet: Buteo japonicus. Downloaded from http://www.birdlife.org on 20/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/02/2020.