6 thoughts on “Blakiston’s Eagle-owl (Bubo blakistoni)”
After conferring with Sergey Surmach (Senior Scientist, Russian Academy of Sciences Far Eastern Branch and Director, ANO WCS), we have the following comments:
Population Size: Since the publication of Slaght et al (2018) we believe that it was improper to extrapolate the Primorye portion of the fish owl population across its entire range in mainland Asia to obtain a global population estimate. Conditions for fish owls (especially unfrozen rivers in winter) seem to be most suitable for fish owls in Primorye, at the southern extent of their range, and degrade as latitude increases. For example, a more recent analysis of one large river drainage north of Primorye (Maya) found no open water at all in winter, precluding use by fish owls, whereas we had thought fish owls might occur there (with an expected number of up to 25 pairs). Consequently, we now lean toward the lower bound of our range for the mainland population (750) than the higher end (1500), and we suggest that this is reflected in the assessment.
Population Trajectory: We have monitored fish owl populations in Primorye for nearly 30 years and have noted steep population declines even here, where the habitat should be most suitable for them. In six river drainages where we monitor fish owls, the population has remained stable along only one (the most remote). In Olga County we began with four pairs and now only one remains. In another population cluster further north (in Terney County), we again monitor only one pair now whereas ten years ago there were four. In the upper Iman River basin we have not detected a fish owl in six years. While the full reasons for these declines are uncertain, climate change is a clear factor as atypically frequent and strong typhoons have resulted in destruction of nest trees and other degradation of habitat.
Subpopulation Structure: We believe that the mainland and island subspecies should be split into two species, following evidence provided by Movin et al (2022), and that the island species retain its status as Endangered.
Range: We believe that Sakhalin Island should be changed from Possibly Extinct to Extinct. From May-July 2023 we conducted a survey for fish owls on Sakhalin Island and found no evidence they persist there. We used a combination of high-quality satellite imagery and field verification methods to identify stretches of open water in the winter months (prey access essential for fish owl occupancy). These sites were also assessed for the presence of sufficiently large trees to support fish owl nests. Due to limited remaining natural resources, we consider Sakhalin Island to have low recovery potential for the species; any efforts would require management interventions such as food supplementation and nest boxes.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments until 25 April 2025. We will now analyse and interpret the information, and we will post a preliminary decision on this species’ Red List category on this page on 25 April 2025, when discussions will re-open.
We thank J. Slaght for his helpful comment above. Based on this, we have revised the number in the largest subpopulation to be 750-1,000. However, since this still exceeds the threshold for Endangered C2a(i), this does not change the proposal to list the species as Vulnerable. We will also change Sakhalin Island to be mapped as extinct.
Regarding the species’ taxonomy, BirdLife is currently committed to aligning its checklist to AviList to ensure congruence with other global taxonomic checklists (see: https://datazone.birdlife.org/about-our-science/taxonomy). Since this list presently treats Blakiston’s Eagle-owl as only one species, we are currently required to assess this species according to the present taxonomy (i.e. one species).
Based on available information, our preliminary proposal for the 2025 Red List would be to adopt the proposed classification outlined in the initial forum discussion.
There is now a period for further comments until the final deadline on 4 May 2025, after which the recommended categorisations will be put forward to IUCN.
The final 2025 Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.
Species distribution probably extends further west that typically shown in range maps although more field evidence is needed, to as far east as the west as the foothills of the Greater Khinggan. Local people in Orqohan has highlighted sight records of the species along several rivers alongside mixed broadleaved forests.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will analyse and interpret the information, and a final decision on this species’ Red List category will be posted on this page on 12 May 2025.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Blakiston’s Eagle-owl is recommended to be listed as Vulnerable under Criteria C2a(i);D1.
Many thanks for everyone who contributed to the 2025.2 GTB Forum process. The final Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.
After conferring with Sergey Surmach (Senior Scientist, Russian Academy of Sciences Far Eastern Branch and Director, ANO WCS), we have the following comments:
Population Size: Since the publication of Slaght et al (2018) we believe that it was improper to extrapolate the Primorye portion of the fish owl population across its entire range in mainland Asia to obtain a global population estimate. Conditions for fish owls (especially unfrozen rivers in winter) seem to be most suitable for fish owls in Primorye, at the southern extent of their range, and degrade as latitude increases. For example, a more recent analysis of one large river drainage north of Primorye (Maya) found no open water at all in winter, precluding use by fish owls, whereas we had thought fish owls might occur there (with an expected number of up to 25 pairs). Consequently, we now lean toward the lower bound of our range for the mainland population (750) than the higher end (1500), and we suggest that this is reflected in the assessment.
Population Trajectory: We have monitored fish owl populations in Primorye for nearly 30 years and have noted steep population declines even here, where the habitat should be most suitable for them. In six river drainages where we monitor fish owls, the population has remained stable along only one (the most remote). In Olga County we began with four pairs and now only one remains. In another population cluster further north (in Terney County), we again monitor only one pair now whereas ten years ago there were four. In the upper Iman River basin we have not detected a fish owl in six years. While the full reasons for these declines are uncertain, climate change is a clear factor as atypically frequent and strong typhoons have resulted in destruction of nest trees and other degradation of habitat.
Subpopulation Structure: We believe that the mainland and island subspecies should be split into two species, following evidence provided by Movin et al (2022), and that the island species retain its status as Endangered.
Range: We believe that Sakhalin Island should be changed from Possibly Extinct to Extinct. From May-July 2023 we conducted a survey for fish owls on Sakhalin Island and found no evidence they persist there. We used a combination of high-quality satellite imagery and field verification methods to identify stretches of open water in the winter months (prey access essential for fish owl occupancy). These sites were also assessed for the presence of sufficiently large trees to support fish owl nests. Due to limited remaining natural resources, we consider Sakhalin Island to have low recovery potential for the species; any efforts would require management interventions such as food supplementation and nest boxes.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments until 25 April 2025. We will now analyse and interpret the information, and we will post a preliminary decision on this species’ Red List category on this page on 25 April 2025, when discussions will re-open.
Preliminary proposal
We thank J. Slaght for his helpful comment above. Based on this, we have revised the number in the largest subpopulation to be 750-1,000. However, since this still exceeds the threshold for Endangered C2a(i), this does not change the proposal to list the species as Vulnerable. We will also change Sakhalin Island to be mapped as extinct.
Regarding the species’ taxonomy, BirdLife is currently committed to aligning its checklist to AviList to ensure congruence with other global taxonomic checklists (see: https://datazone.birdlife.org/about-our-science/taxonomy). Since this list presently treats Blakiston’s Eagle-owl as only one species, we are currently required to assess this species according to the present taxonomy (i.e. one species).
Based on available information, our preliminary proposal for the 2025 Red List would be to adopt the proposed classification outlined in the initial forum discussion.
There is now a period for further comments until the final deadline on 4 May 2025, after which the recommended categorisations will be put forward to IUCN.
The final 2025 Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.
Species distribution probably extends further west that typically shown in range maps although more field evidence is needed, to as far east as the west as the foothills of the Greater Khinggan. Local people in Orqohan has highlighted sight records of the species along several rivers alongside mixed broadleaved forests.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will analyse and interpret the information, and a final decision on this species’ Red List category will be posted on this page on 12 May 2025.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Blakiston’s Eagle-owl is recommended to be listed as Vulnerable under Criteria C2a(i);D1.
Many thanks for everyone who contributed to the 2025.2 GTB Forum process. The final Red List categories will be published on the BirdLife and IUCN websites in October 2025, following further checking of information relevant to the assessments by both BirdLife and IUCN.