Bubo blakistoni

Geographic Range

Blakiston's fish owls occur only in select areas of northeast Asia. The enigmatic birds are found in eastern Siberia, northern China, North Korea, and northern Japan.

• Biogeographic Regions
• palearctic palearctic
  • native native

Habitat

Blakiston's fish owls require year-round open water to feed. They also need large trees for nesting cavities, and therefore are often found in riparian forests. Most of the surrounding woodlands are coniferous spruce and firs, or mixed deciduous forests with maple , ash and elm .

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

• Other Habitat Features
• riparian riparian

Physical Description

Bubo blakistonii looks much like brown fish owls ( Bubo zeylonensis ) of Asia. It is also one of the largest owl species in the world. 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.

The bill is long and curved and color ranges from grayish-blue to brown. The large claws are black and the tarsis are feathered in front. The iris is yellow. Bubo blakistoni is a large owl with a length of 60 to 71 cm and a wingspan of up to 2 m. Its weight ranges from 2.7 to 4 kg, and the males are smaller than the females.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Blakiston's fish owls tend to stay in pairs throughout the year. Male and female tend to be monogamous for many years.

• Mating System
• monogamous monogamous

Blakiston's fish owls do not breed every year; every two or three years is more typical. The young reach full size in 6 weeks and take up to 7 weeks to fledge. Fledgers still may remain in the area for up to a year and a half before they go off on their own. Once independent, the fish owl reaches sexual maturity at three years of age.

Blakiston's fish owls may select nest sites high up (2 to 18 m) in old-growth trees but have also been seen nesting on fallen trees on the forest floor. Laying begins in early spring and the pair typically has one to two eggs per two year interval. It takes about 35 days for eggs to hatch.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

In Blakiston's fish owls, females perform egg incubation while males hunt for food. After the chicks have hatched, the female begins to join the male in night foraging. Investment in the young is high for this species; parents care for offspring up to two months and even share territories with valuable river access with them for up to a year after they are independent. Harsh conditions of the habitat may be cause for such high attention to young.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• post-independence association with parents

Lifespan/Longevity

No numbers were found in the literature, however, lifespan is thought to be similar to other fish owls found in the wild in Asia, approximately eight to fifteen years.

Behavior

Blakiston's fish owls are excellent hunters of the fish in rivers and lakes. With extraordinary vision they primarily hunt at dusk and night, but it is not uncommon for them to hunt in the day as well. Sometimes they swoop down from a tree along the bank to snatch fish if the water is not iced over. Blakiston's fish owls are known to spend a good deal of time on the ground, and during winter, tread over snow to hunt ice pockets. Some birds have even been observed wading in shallow water to catch crayfish and amphibians.

• Key Behaviors
• flies
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

While research is being conducted to better understand the range distribution of this species, observation has shown that a pair of fish owls usually only occupies an area of about 2.6 square kilometers, so long as there is access to water. Due to harsh winter conditions, Blakiston's fish owls may seasonally relocate for a more suitable hunting environment.

Communication and Perception

Calls by adults are identified by a ‘boo-boo uoo’ or ‘foo-foroo’. Adults perform duets, where males and females call 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 occurs only when the pair is agitated.

Like all owls, Blakiston's fish owls rely heavily on visual and auditory stimuli, and feature unique physical adaptations. The facial disk feather arrangement serves to gather sounds and increase accuracy when detecting prey movement. Large, immobile eyes allow the owls to capture enough light to hunt prey at night.

• Communication Channels
• acoustic acoustic

• Other Communication Modes
• duets duets

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Bubo blakistonii mainly feeds on fish, and depends on open water or holes in the ice where it may fly down and make use of its powerful claws. It also hunts on the ground and in shallow water for crayfish and frogs. Mammals and waterfowl may occasionally be consumed in icy winters when water has frozen completely.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• birds
• mammals
• amphibians
• fish
• aquatic crustaceans

Predation

No known predators were found in the literature.

Ecosystem Roles

Blakiston's fish owls impact the populations of fish, small vertebrate, and other organisms they feed on.

Economic Importance for Humans: Positive

The regions where Blakiston's fish owls are found are largely unpopulated by humans and there are no direct links reported between this species and humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Blakiston's fish owls on humans.

Conservation Status

IUCN Red List recognizes this species as a rare and endangered bird. Despite not living among humans, this species occurs in timber rich areas that are valued for their natural resources, primarily in Japan and Russia. As such, habitat destruction by the logging industry is a concern for this species. Poachers have been known to kill Blakiston's fish owls. With an estimated 5,000 individuals remaining in the wild, saving every bit of forest and enforcing species management is of dire importance.

Additional Links

Encyclopedia of Life

Contributors

Erik Oien (author), Florida State University, Emily DuVal (editor), Florida State University.

References

Burton, P. 1973. Owls of the World: Their evolution, structure and ecology . New York: Dutton&Co.

Dinerstein, E. K. O. W. 1994. An Emergency Plan to Rescue Russia's Biological Diversity. Conservation Biology , Vol. 8 no. 4: 934-939.

Hayashi, Y. 1997. Home range, habitat use and natural dispersal of Blakiston fish owl. Raptor Research , Vol. 31: 283-285.

Konig, C., B. Weick. 1999. A Guide to the Owls of the World. . New Haven: Yale University Press.

Slaght, J., S. Surmach. 2008. Biology and Conservation of Blakiston's fish owls. Raptor Research , Vol. 40: 29-37.

Slaght, J. 2009. Chasing a Giant. Wildlife Conservation , March/April: 10-15.