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 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.
Ferguson-Lees and Christie (2001) estimate the population at 20,000-30,000 pairs which equates to 40,000 to 60,000 mature individuals. The species is described as generally rare in Russia and uncommon in northern Japan (del Hoyo et al. 1992).
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.
Degradation of wetland habitat across the species's range (Orta et al. 2014). In Japan, lead shot in prey items has been identified as a potential threat (Hirano et al. 2004); this threat could be more widespread across the species's range.
Text account compilers
Butchart, S., Ekstrom, J., Symes, A., Taylor, J. & Ashpole, J
BirdLife International (2020) Species factsheet: Circus spilonotus. Downloaded from http://www.birdlife.org on 10/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 10/08/2020.