Blakiston's Fish-Owl Ketupa blakistoni Scientific name definitions

60–71 cm (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ); nominate: male 3150–3450 g (n = 3), female 3360–4600 g (n = 4) (2 Hayashi, Y. (2010). Blakiston’s Fish Owl. Bird Research News 7(2): 4-5. Close ); race doerriesi: male 3100 g (mean of 7), female 3250 (mean of 5) (3 Slaght, J.C. (2011). Management and Conservation Implications of Blakiston's Fish Owl (Ketupa blakistoni) Resource Selection in Primorye, Russia. PhD dissertation, University of Minnesota, Minneapolis. Close ); wingspan 178–190 cm (4 Mikkola, H. (2014). Owls of the World. A Photographic Guide. 2nd edition. Firefly Books, Buffalo, NY, USA. Close ). After Bubo bubo, the largest of all owls (5 Mikkola, H. (2017). The Eurasian Eagle Owl is the largest living owl species! Tyto. 12(1): 15-18. Close ); ear tufts broad, long, typically held horizontal. Facial disc pale grey-brown; upperparts buff-brown, broadly streaked, wings barred buff and dark brown; tail almost white, barred dark; white throat; below, pale buffish-brown with long, thin streaks; tarsi feathered almost to base of toes; irides yellow; cere and bill pale grey-horn, latter yellowish at tip; toes lead-grey (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Juvenile with spots and whitish feather edgings above; bill and toes bluish (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Race doerriesi larger (wing length 510–560 mm versus 498–534 mm in nominate (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ) ), with white crown patch.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Dense, old-growth broadleaf or mixed broadleaf/coniferous forest along clear rivers, favouring tributary confluences where some slow-flowing channels; steep-sided wooded valleys near fast-flowing rivers; also taiga rivers which do not freeze in winter; in Kurils, dense conifer forest adjacent to water, including sea coast. Also forages on rocky coasts. Lowlands. Extensive study in Primorye, Russia, revealed preference for home ranges within valleys that were close to water and had more river channels than available sites; large trees and riparian old-growth forest distinguished nest sites and foraging sites from surrounding areas; old forests had numerous large trees that provided large woody debris in rivers, which improved habitat for salmonid prey (3 Slaght, J.C. (2011). Management and Conservation Implications of Blakiston's Fish Owl (Ketupa blakistoni) Resource Selection in Primorye, Russia. PhD dissertation, University of Minnesota, Minneapolis. Close ).

Generally considered resident, but seasonal movements poorly understood (6 Slaght, J.C. and Surmach, S.G. (2008). Biology and conservation of Blakiston's Fish-Owls (Ketupa blakistoni) in Russia: a review of the primary literature and an assessment of the secondary literature. Journal of Raptor Research. 42(1): 29-37. Close ). Young birds may wander widely before settling on a nesting territory (7 Hayashi, Y. (1997). Home range, habitat use and natal dispersal of Blakiston’s Fish-Owls. Journal of Raptor Research. 31(3): 283-285. Close ). In Russia, mean annual home range size for seven adults was 15.0 ± 3.7 km² using the synoptic model and 38.8 ± 15.4 km² using kernel-density estimator (3 Slaght, J.C. (2011). Management and Conservation Implications of Blakiston's Fish Owl (Ketupa blakistoni) Resource Selection in Primorye, Russia. PhD dissertation, University of Minnesota, Minneapolis. Close ).

Primarily fish , including large ones; also crabs, crayfish, frogs (especially in spring (6 Slaght, J.C. and Surmach, S.G. (2008). Biology and conservation of Blakiston's Fish-Owls (Ketupa blakistoni) in Russia: a review of the primary literature and an assessment of the secondary literature. Journal of Raptor Research. 42(1): 29-37. Close ) ), and birds up to size of grouse (Tetraonidae); occasionally bats in flight. In autumn and winter, diet includes crayfish and other crustaceans as well as small mammals; sometimes cats and small dogs. Forages mainly at night (fish) or dusk (frogs); also by day. Hunts from low branch, log or bank overlooking river shallows; often walks about on ground, occasionally wades in shallow water (6 Slaght, J.C. and Surmach, S.G. (2008). Biology and conservation of Blakiston's Fish-Owls (Ketupa blakistoni) in Russia: a review of the primary literature and an assessment of the secondary literature. Journal of Raptor Research. 42(1): 29-37. Close ); jumps on prey and kills with talons ; sometimes swoops to catch fish near surface, or dives feet first into deep water. In winter , will wait by holes in ice or snow; sometimes up to 5–6 individuals together.

Territorial call short, deep “boo-boo-voo”  or “shoo-hoo”; elaborate duets; begging call of young a long, slurred “peer-peer-peer” (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

Lays late Feb-mid Mar, when snow cover still deep. Probably pairs for life. Nest a spacious hole up to 18 m above ground in large hollow tree, or in nest box, or in fallen tree; 15 nests in Primorye ranged from 4–16·8 m above ground (3 Slaght, J.C. (2011). Management and Conservation Implications of Blakiston's Fish Owl (Ketupa blakistoni) Resource Selection in Primorye, Russia. PhD dissertation, University of Minnesota, Minneapolis. Close ). Highly territorial, in Siberia territory covering 6–12 km of river valley, but density much higher in Primorye with 1 pair / per 3·8 km of river (6 Slaght, J.C. and Surmach, S.G. (2008). Biology and conservation of Blakiston's Fish-Owls (Ketupa blakistoni) in Russia: a review of the primary literature and an assessment of the secondary literature. Journal of Raptor Research. 42(1): 29-37. Close ). Courtship feeding begins 4 days before first copulation; most copulations around sunset. Clutch size usually 2 eggs (1–3); egg size 55·9–69·4 mm × 49·0–52·8mm (2 Hayashi, Y. (2010). Blakiston’s Fish Owl. Bird Research News 7(2): 4-5. Close ); incubation 35–37 days, by female, fed on nest 3–5 times nightly by male; female leaves only to defecate and preen, travelling no more than 100 m from nest; chick with white down; young leave nest at 35–40 days, remain with parents for several months; juveniles sometimes dependent on adults for up to 1 year, especially during harsh winters. Apparently breeds only in alternate years. Lifespan probably 20 years or more. Sex ratio of fledglings male-biased, with 81 males and 56 females in sample of 137 young from 91 broods (8 Hayashi, Y. and Nishida-Umehara, C. (2000). Sex ratio among fledglings of Blakiston’s Fish Owls. Japanese Journal of Ornithology. 49(3): 119-129. Close ). Several records of close inbreeding on Hokkaido, including pairings by a father and daughter, grandmother and grandson, and full siblings (albeit hatched in different years) (9 Hayashi, Y. (2009). Close inbreeding in Blakiston’s Fish-Owl (Ketupa blakistoni). Journal of Raptor Research. 43(2): 145-148. Close ).

ENDANGERED. CITES II. One of world’s rarest, and until fairly recently most poorly known owls. Numbers in Russia, including Sakhalin and S Kuril Is, estimated at 300–400 pairs in 1984, but 250–400 birds subsequently found in Primorye alone BirdLife International (2016) Species factsheet: Bubo blakistoni. Downloaded from http://www.birdlife.org on 22/07/2016. ; formerly present throughout Hokkaido (Japan), but now confined to E & C parts, where 140 individuals occur (an increase on the 80–100 birds estimated in late 1980s attributed to provision of articifial nest sites and feeding) (10 Omote, K., Nishida, C., Takenaka, T., Saito, K., Shimura, R., Fujimoto, S., Sato, T. and Masuda, R. (2015). Recent fragmentation of the endangered Blakiston’s Fish Owl (Bubo blakistoni) population on Hokkaido Island, northern Japan, revealed by mitochondrial DNA and microsatellite analyses. Zoological Letters 1:16. Close ), with only c. 20 pairs breeding in any year; in NE China extremely rare and local, possibly now extinct. Global population may be "a few thousand birds", and conservatively put at fewer than 2500 mature individuals BirdLife International (2016) Species factsheet: Bubo blakistoni. Downloaded from http://www.birdlife.org on 22/07/2016. . Has declined massively over entire range, especially since 1950s; on R Bikin, in Ussuriland, decrease from estimated 70 birds (26 pairs) in mid 1970s to current total of 15 pairs or fewer. Range and population now fragmented. Main threats are development of riverside habitats and deforestation, especially destruction of taiga forest in Far East and Japan; on lower R Bikin, human population pressure forcing it to move to less productive rivers. In a Russian study, 43% of optimal fish-owl habitat was within current logging leases, while protected areas included only 19% (11 Slaght, J.C. and Surmach, S.G. (2016). Blakiston’s Fish-owl Bubo blakistoni and logging: Applying resource selection information to endangered species conservation in Russia. Bird Conservation International. 26(2): 214-224. Close ). Depletion of fish stocks through overfishing also an adverse factor, and water pollution is a further threat. Direct mortality often human-induced (6 Slaght, J.C. and Surmach, S.G. (2008). Biology and conservation of Blakiston's Fish-Owls (Ketupa blakistoni) in Russia: a review of the primary literature and an assessment of the secondary literature. Journal of Raptor Research. 42(1): 29-37. Close ). This species’ habit of concentrating around fishing holes in Siberia renders it vulnerable to hunters and fishermen; also persecuted by fur-trappers, and sometimes dies in traps set for mink; hunted for food locally in Siberia. On Hokkaido, mortality has been caused by collision with powerlines and traffic as well as by drowning in nets employed on fish farms BirdLife International (2016) Species factsheet: Bubo blakistoni. Downloaded from http://www.birdlife.org on 22/07/2016. . Hokkaido population shows low genetic diversity, indicating a recent population bottleneck and fragmentation (10 Omote, K., Nishida, C., Takenaka, T., Saito, K., Shimura, R., Fujimoto, S., Sato, T. and Masuda, R. (2015). Recent fragmentation of the endangered Blakiston’s Fish Owl (Bubo blakistoni) population on Hokkaido Island, northern Japan, revealed by mitochondrial DNA and microsatellite analyses. Zoological Letters 1:16. Close ). Provision of nest boxes has achieved some success on Kunashiri I and Hokkaido, where pairs have bred in these artificial nests annually since 1983. Attempts at captive-breeding unsuccessful. Legally protected throughout its range BirdLife International (2016) Species factsheet: Bubo blakistoni. Downloaded from http://www.birdlife.org on 22/07/2016. . On the basis of recent research in Russia (3 Slaght, J.C. (2011). Management and Conservation Implications of Blakiston's Fish Owl (Ketupa blakistoni) Resource Selection in Primorye, Russia. PhD dissertation, University of Minnesota, Minneapolis. Close ), management recommendations include protecting specific locations within potential territories, maintaining integrity of riparian areas, modifying road construction techniques, and closing old logging roads to reduce human access; these actions would benefit the owls as well as many other species, because the owl is an “umbrella species” for riparian ecosystems within the region (3 Slaght, J.C. (2011). Management and Conservation Implications of Blakiston's Fish Owl (Ketupa blakistoni) Resource Selection in Primorye, Russia. PhD dissertation, University of Minnesota, Minneapolis. Close , 12 Higa, M., Yamaura, Y., Senzaki, M., Koizumi, I., Takenaka, T., Masatomi, Y. and Momose, K. (2016). Scale dependency of two endangered charismatic species as biodiversity surrogates. Biodiversity and Conservation. 25(10): 1829-1841. Close ).