BLACKISTON’S FISH OWLS: CHARACTERISTICS, BEHAVIOR, CONSERVATION

BLACKISTON’S FISH OWLS

Blakiston's fish owl

Blakiston's fish owls (Bubo blakistoni) are the world's largest owls. Found in Hokkaido, the Russian Far East (eastern Siberia), northern China, North Korea, and the Russian islands of Sakhalin, Kunashiri and Etorofu, they have a wing span of 1.8 meters (six feet) and head and body length of 70 centimeters (2.3 feet) and weighs four kilograms (8.8 pound). The Ainu people of northern Japan gave these birds many names and revered them as guardians of villages and gods that cry at night and protects the country. The Japanese have traditionally associated owls with happiness and good luck and are fond of buying owl ornaments.

Blakiston's fish owls They live in cold, temperate areas with a climate similar to those of the northern U.S., Canada and Europe. They require year-round open water to feed. They also need large trees for nesting cavities, and therefore are often found in riparian forests adjacent to rivers, welands, estuaries or the sea. The woodlands they live in tend to be forests made up of coniferous spruce and firs, or mixed deciduous trees with beech, maple, ash and elm.[Source: Erik Oien, Animal Diversity Web (ADW) /=]

Blakiston's fish owls are also known as Blakiston's eagle owls. They are named after Thomas Wright Blakiston, a British businessman and amateur naturalist who lived in Hokkaido in the late 1800s, and ironically has as much to do with the bird’s demise as anyone. After bringing lumber equipment half way around the world to harvest timber in eastern Siberia he was denied permission to take the trees there in 1861 and instead came to Hokkaido where he hauled away timber from the island’s rich old-growth forests.

Bird Guidebooks “Guide to the Birds of China” by John MacKinnon (Oxford University Press), “A field Guide to the Birds of Russia and Adjacent Territories” by V.E. Flint (Princeton University Press)and a “Birdwatchers's Guide to Japan” by Mark Brazil (Kodansha). Birding Websites: Birds of Japan Gallery by Monte Taylor Birds of Japan ; Birding Hotspots JapanBirding Hotspots Birdwatching in Japan Birding Pal; Bird Life International birdlife.org Blakiston's Fish Owl Blakiston's Fish Owl Project fishowls.com ;

Blakiston’s Fish Owl Characteristics and Diet

Blakiston’s fish owls range in weight from 2.7 to four kilograms (5.95 to 8.81 pounds) and have a head and body length that ranges from 60 to 71 centimeters (23.6 to 27.9 inches). Their wingspan ranges reaches two meters (6.56 feet). They are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them) and warm-blooded (homoiothermic, have a constant body temperature, usually higher than the temperature of their surroundings). Sexual Dimorphism (differences between males and females) is present: Females are larger than males. [Source: Erik Oien, Animal Diversity Web (ADW) /=]

Blakiston's fish owl range

Blakiston’s fish owls are the largest owl species in the world as we said before. They look a lot like brown fish owls (Bubo zeylonensis) of Asia but are bigger. Blakiston's fish owls have partially flattened feathers surrounding their faces (a feature of all owls) also known as 'facial disks' that give them a flat-faced appearance. They also have large, full-feathered ear tufts. Facial plumage is tan with black stripes and the brow of the eye has a thin row of white feathers. The wings and tail are a dark brown with yellowish stripes and the underside plumage is light brown with thin vertical black stripes. Their bill is long and curved and the color ranges from grayish-blue to brown. The large claws are black and the tarsis are feathered in front. The iris is yellow.

Blakiston’s fish owls are primarily carnivores (eat meat or animal parts) and also recognized as piscivores (eat fish). They feed primarily on fish. In Japan they primarily eat freshwater fish such as “ayu” (sweetfish), salmon and trout as well as the occasional rodent. They tend to catch prey on open water or holes in the ice and often swoop down and make use of their powerful claws to grab prey. They also hunt crayfish and frogs taken off the ground and in shallow water. . Mammals and waterfowl are most likely to be hunted during the icy winters when water has frozen completely.

Blakiston’s Fish Owl Behavior

Blakiston's fish owls like most owls are solitary, nocturnal (active at night) and good fliers. They are motile (move around as opposed to being stationary), sedentary (remain in the same area), territorial (defend an area within the home range). [Source: Erik Oien, Animal Diversity Web (ADW) /=]

The average territory of a Blakiston's fish owl pair is around 2.6 square kilometers (one square mile). Observations have shown that a pair of fish owls usually only stays within their home range as long as there is access to water and enough food. During the harsh winter, they may relocate to a different place with more available food.

Blakiston's fish owls are superb hunters of fish in rivers and lakes. Utilizing their acute night vision, they primarily hunt at dusk and night, but it is not unusual to them hunting in the day as well. Sometimes they swoop down from a tree along a river or lake to snatch fish if the water is not frozen. Blakiston's fish owls are known to spend a lot of time on the ground. During the winter, tread over snow seeking out air pockets where prey might be. Some birds have been observed wading in shallow water to catch crayfish and amphibians.

Blakiston’s Fish Owl Senses and Communication

Blakiston's fish owl hunting for fish

Blakiston's fish owls sense using vision, touch, sound and chemicals usually detected with smell. They communicate with sound and employ duets (joint displays, usually between mates, and usually with highly-coordinated sounds) to communicate. Male and females call each other with a closely synchronized “ bo-bohhh”, “ bo-bohhh” that sounds likes they are coming from a single bird.

Calls by adults are identified by a ‘boo-boo uoo’ or ‘foo-foroo’. During the duets performed by adults, males and females call each other in quick succession. The pattern changes across populations but for those on the mainland, males contribute the first and third notes and females contribute the second and fourth. Occasionally the order is reversed with the female initiating the duet, but this mainly occurs only when the pair is agitated.

Like all owls, Blakiston's fish owls rely heavily on vision and sound to hunt, sense and communicate and have physical adaptations to enhance these senses. The facial disk feather arrangement acts like a satellite disc, gathering and focusing sounds to the enhance the owl’s ability to detect prey movement. Large, immobile eyes allow the owls to capture minute amounts light to hunt prey in darkness.

Blakiston’s Fish Owl Mating, Reproduction and Offspring

Blakiston's fish owls are monogamous (having one mate at a time) and tend to stay in pairs throughout the year and often many years. They engage in seasonal breeding. On average, Blakiston's fish owls breed once every two or three years from early spring to summer. The number of eggs laid each season ranges from one to three. The average time to hatching is 35 days. The average fledging age is seven weeks and the average time to independence is 1.5 years. Females and males reach sexual or reproductive maturity at two to three. [Source: Erik Oien, Animal Diversity Web (ADW) /=]

Blakiston's fish owls prefer nest sites two to 18 meters high in old-growth trees but have also been observed nesting in fallen trees on the forest floor. Young are are altricial, meaning that they are born relatively underdeveloped and are unable to feed or care for themselves or move independently for a period of time after birth. Parental care is provided by both females and males. During the pre-birth, pre-weaning and pre-independence stages of young provisioning and protecting are done by males and females. The post-independence period is characterized by the association of offspring with their parents.

Among Blakiston's fish owls, females perform egg incubation while males hunt for food. After the chicks have hatched, the female to joins the male during their nightly searches for food. Investment in young is high for this species. Parents spend a lot of time caring for offspring, don’t breed every year and share valuable territories with water access with them for up to a year after they are independent. Harsh winter conditions may one reason for this. Young reach full size in six weeks and fledge at seven weeks. /=\

Endangered Blackiston’s Fish Owls, Humans and Conservation

On the International Union for Conservation of Nature (IUCN) Red List,Blakiston's fish owls are listed as Endangered. There are about 130 birds living in Hokkaido. This is better than 1984, when there were 30 or 40. Naturalists hope the number will increase to 200 in the not too distant future. To help them conservationists have built over 100 government-funded nesting boxes and handful of winter feeding stations, where naturalists leave out fish because the owls can not catch fish in frozen rivers. There are plans to make tree corridors to link forested areas together.

On mainland Asia the population of Blakiston's fish owls is estimated at several hundred or perhaps up to thousands of individuals. Globally, there are estimated to be 1,000 to 1,500 individuals, or about 500 to 850 pairs. In the Primorye region of the Russian Far East an estimated that 200 to 400 individuals remain. A 2016-2019 survey on Kunashir Island found 28 pairs. [Source: Wikipedia]

The regions where Blakiston's fish owls are found are largely unpopulated by humans but they rich in timber and fish. Reasons for the Blakiston's fish owl's decline include overfishing, cars, power lines, the loss of habitat through deforestation — particularly in old growth forests where the owls do best — and development — particularly the damming and draining rivers. The owls used to be found all over Hokkaido but their numbers began to fall in the late 19th and early 20th century when the old growth forests were cut down and the damming and channeling of rivers eliminated most of the large fish runs. In Russia, fish owls have been killed by fur-trappers, drown in nets set for salmon, and are shot by hunters. Exposure to lead or lead poisoning, possibly from bioaccumulation but also perhaps lead bullets in carrion, have been reported in these owls in at least Japan.

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, BBC, CNN, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated March 2025