Blakiston's Fish Owl
Encyclopedia
Blakiston's Fish Owl, Bubo blakistoni, is a fish owl, a sub-group of eagle owls who specialized in hunting riparian areas. This species is a part of the family
known as typical owl
s, Strigidae, which contains most species of owl. Blakiston's Fish Owl and three related species were previously placed in the genus Ketupa; mtDNA cytochrome b
sequence
data is equivocal on which genus name is applied for this species (Olsen et al. 2002).
Its habitat is riparian forest, with large, old trees for nest-sites, near lakes, rivers, springs and shoals which don't freeze in winter.
of 150–205 cm (60–81 in). Superficially, this owl looks like the Eurasian Eagle-Owl, but is paler, and has broad, ragged ear tufts. The upperparts are buff-brown and heavily streaked. The underparts are pale buffish-brown. The throat is white. The iris is yellow (whereas the Eurasian Eagle-Owl has an orange iris). Vocalizations differ among the recognized subspecies. In the island subspecies, the male calls twice and the female responds with one note, whereas the mainland subspecies has a somewhat more elaborate, 4-note duet:"HOO-hoo, HOOO-hoooo" (here, the male call is in capital letters (HOO) and the female call in lower case (hoo)). This duet is so synchronized that those unfamiliar with the call often think it is only one bird calling. When an individual bird calls, it sounds like hoo-hooo. Juveniles have a characteristic shriek.
B. b. blakistoni (Seebohm, 1884). Hokkaido
, N. Japan
and Kuriles. Lores of facial disc tawny-brown with narrow black shaft-stripes; above eyes, around bill base and on forehead a row small, stiff almost completely white feathers; chin largely white. Rest of head and underparts brown with blackish-brown shaft-stripes and buff feather tips; back is darker. The mantle is somewhat lighter and more rufous and with blackish-brown bars as well as dark brown shaft-streaks. Wings deep brown with numerous buffy-yellow bars. Tail dark brown with 7-8 cream-yellow bars. Underparts light buff-brown with blackish-brown shaft streaks and narrow light brown wavy cross-bars.
B. b. doerriesi (Seebohm, 1884). E. Siberia
south to Vladivostok
region and Korea
n border area. Larger than nominate with large white patch on top of the head; tail less marked and bars incomplete.
B. b. karafutonis (Kuroda, 1931). Sakhalin
. Smaller than nominate race and darker, especially on back and ear-coverts; tail with narrower dark brown bars and the light bars more numerous (8-9 against 7 in nominate).
B. b. piscivorus (Meise, 1933). W. Manchuria
. Paler overall than doerriesi, ground color of underparts grayish-white (not buff-brown); tail-bars not fully creamy-yellow, central rectrices having white inner webs almost to base; chin pure white.
, with common prey including pike
, catfish
, burbot
, trout
and salmon
. Some fish these owls catch are quite large, weighing at least as much as the owl. In Russia, amphibians are taken in great quantity in spring, especially Dybowski's frog
. The two most common hunting methods for Blakiston's Fish Owl are wading through river shallows, and perching on the river bank and waiting for movement in the water. A wide variety of mammal
ian prey are described from Japan, including rodent
s and marten
s. Fewer records are known of bird predation, but birds hunted are known to the size of hazel grouse
(Slaght and Surmach 2008). It also takes carrion, as evidenced by fish owls in Russia being trapped in snares set for furbearing mammals, which use raw meat as bait (Slaght and Surmach 2008).
These owls are primarily active at dusk and dawn. During the brood-rearing season, these owls are most often seen active during the day. For an owl, it spends unusual amounts of time on the ground. Early reports of concentrations of as many as 5-6 owls near rapids and non-freezing springs are dubious records, as these owls are highly territorial (Slaght and Surmach 2008).
nests (Takenaka 1998, Yamamoto 1999). Nest cavities have to be quite large in order to accommodate these birds. Clutch size is 1 to 3, usually 2 (Yamamoto 1999). In Russia, clutches are usually just one egg (Slaght and Surmach 2008). Eggs are 6.2 cm (2.5 in) long and 4.9 cm (1.9 in) wide. The males provide food for the incubating female and later the nestlings. The incubation period is about 35 days and young leave the nest within 35–40 days but are often fed and cared for by their parents for several more months. Juveniles linger on their parents' territory for up to two years before dispersing to find their own territory. Once full-sized, these owls have few natural predators. There is one record of an adult fish owl being stalked and killed by a Eurasian lynx
in Russia, while the owl hunted along a river bank (Yelsukov 2005, cited in Slaght and Surmach 2008).
The Blakiston's Fish Owl is endangered due to the widespread loss of riverine forest, increasing development along rivers and dam construction. The current population in Japan is approximately 100-150 birds (20 breeding pairs and unpaired individuals), whereas on mainland Asia the population is higher, variously estimated at several hundred or perhaps thousands of individuals (Slaght and Surmach 2008). In Russia, fish owls are killed by fur-trappers (see above), drown in nets set for salmon, and are shot by hunters (Slaght and Surmach 2008). In Japan, death by hunting is unlikely, but fish owls have been hit and killed by cars (Yanagawa 1993). Local conservation efforts in Japan have been undertaken including education and installation of large nest-boxes.
Henry Seebohm named this bird after the English naturalist Thomas Blakiston
, who collected the original specimen in Hakodate on Hokkaidō
, Japan in 1883.
peoples of Hokkaido, Japan as a Kamuy (divine being) called Kotan koru Kamuy (God that Protects the Village). In Russia, the species is currently considered a food source by the Evens
people in northern Siberia
and the northern Russian Far East
. Previously, fish owls were hunted as a food source by the Udege
peoples in Primorye
, but this practice has fallen out of favor in recent times (Slaght and Surmach 2008).
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
known as typical owl
Typical owl
True owl or Typical owl are one of the two generally accepted families of Owls, the other being the barn owls . The Sibley-Ahlquist taxonomy unites the Caprimulgiformes with the owl order; here, the typical owls are a subfamily Strigidae...
s, Strigidae, which contains most species of owl. Blakiston's Fish Owl and three related species were previously placed in the genus Ketupa; mtDNA cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...
sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data is equivocal on which genus name is applied for this species (Olsen et al. 2002).
Its habitat is riparian forest, with large, old trees for nest-sites, near lakes, rivers, springs and shoals which don't freeze in winter.
Description
Blakiston's Fish Owl is possibly the largest species of owl at 60–75 cm (24–30 in). A recent field study of the species showed males weighing from 3 to 3.75 kg (6.6-8.3 lbs), with the female, at up to 4.5 kg (10 lbs), about 25% larger. The reported wingspanWingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
of 150–205 cm (60–81 in). Superficially, this owl looks like the Eurasian Eagle-Owl, but is paler, and has broad, ragged ear tufts. The upperparts are buff-brown and heavily streaked. The underparts are pale buffish-brown. The throat is white. The iris is yellow (whereas the Eurasian Eagle-Owl has an orange iris). Vocalizations differ among the recognized subspecies. In the island subspecies, the male calls twice and the female responds with one note, whereas the mainland subspecies has a somewhat more elaborate, 4-note duet:"HOO-hoo, HOOO-hoooo" (here, the male call is in capital letters (HOO) and the female call in lower case (hoo)). This duet is so synchronized that those unfamiliar with the call often think it is only one bird calling. When an individual bird calls, it sounds like hoo-hooo. Juveniles have a characteristic shriek.
Subspecies
Of the following four subspecies described in the literature, only the first two (B. b. blakistoni & B. b. doerriesi) are accepted by science (Slaght and Surmach 2008). The other two (B. b. karafutonis and B. b. piscivorus) are now thought to be extinct and are present only for historical interest.B. b. blakistoni (Seebohm, 1884). Hokkaido
Hokkaido
, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island; it is also the largest and northernmost of Japan's 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaido from Honshu, although the two islands are connected by the underwater railway Seikan Tunnel...
, N. Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Kuriles. Lores of facial disc tawny-brown with narrow black shaft-stripes; above eyes, around bill base and on forehead a row small, stiff almost completely white feathers; chin largely white. Rest of head and underparts brown with blackish-brown shaft-stripes and buff feather tips; back is darker. The mantle is somewhat lighter and more rufous and with blackish-brown bars as well as dark brown shaft-streaks. Wings deep brown with numerous buffy-yellow bars. Tail dark brown with 7-8 cream-yellow bars. Underparts light buff-brown with blackish-brown shaft streaks and narrow light brown wavy cross-bars.
B. b. doerriesi (Seebohm, 1884). E. Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
south to Vladivostok
Vladivostok
The city is located in the southern extremity of Muravyov-Amursky Peninsula, which is about 30 km long and approximately 12 km wide.The highest point is Mount Kholodilnik, the height of which is 257 m...
region and Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
n border area. Larger than nominate with large white patch on top of the head; tail less marked and bars incomplete.
B. b. karafutonis (Kuroda, 1931). Sakhalin
Sakhalin
Sakhalin or Saghalien, is a large island in the North Pacific, lying between 45°50' and 54°24' N.It is part of Russia, and is Russia's largest island, and is administered as part of Sakhalin Oblast...
. Smaller than nominate race and darker, especially on back and ear-coverts; tail with narrower dark brown bars and the light bars more numerous (8-9 against 7 in nominate).
B. b. piscivorus (Meise, 1933). W. Manchuria
Manchuria
Manchuria is a historical name given to a large geographic region in northeast Asia. Depending on the definition of its extent, Manchuria usually falls entirely within the People's Republic of China, or is sometimes divided between China and Russia. The region is commonly referred to as Northeast...
. Paler overall than doerriesi, ground color of underparts grayish-white (not buff-brown); tail-bars not fully creamy-yellow, central rectrices having white inner webs almost to base; chin pure white.
Feeding and Behavior
It feeds on a variety of aquatic prey. The main prey is fishFish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, with common prey including pike
Pike
-Transit:*Pike or toll road, a course in which fees are collected. Sometimes a historical name of what once was a toll road.-Fish:*Esox, genus of pikes**Northern pike, common north hemisphere pike*Blue pike or blue walleye, an extinct freshwater fish...
, catfish
Catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
, burbot
Burbot
The burbot is the only gadiform fish inhabiting freshwaters. It is also known as mariah, the lawyer, and eelpout. It is closely related to the marine common ling and the cusk...
, trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
and salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
. Some fish these owls catch are quite large, weighing at least as much as the owl. In Russia, amphibians are taken in great quantity in spring, especially Dybowski's frog
Dybowski's frog
The Dybowski's frog, Rana dybowskii, is a species of true frog found in Northeast Asia. It is found in the Russian Far East, the Korean Peninsula, and the Japanese island of Tsushima...
. The two most common hunting methods for Blakiston's Fish Owl are wading through river shallows, and perching on the river bank and waiting for movement in the water. A wide variety of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian prey are described from Japan, including rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s and marten
Marten
The martens constitute the genus Martes within the subfamily Mustelinae, in family Mustelidae.-Description:Martens are slender, agile animals, adapted to living in taigas, and are found in coniferous and northern deciduous forests across the northern hemisphere. They have bushy tails, and large...
s. Fewer records are known of bird predation, but birds hunted are known to the size of hazel grouse
Hazel Grouse
The Hazel Grouse or Hazel Hen is one of the smaller members of the grouse family of birds. It is a sedentary species, breeding across northern Eurasia and central and eastern Europe in dense, damp, mixed coniferous woodland, preferably with some spruce.The nest is on the ground, and 3–6 eggs is...
(Slaght and Surmach 2008). It also takes carrion, as evidenced by fish owls in Russia being trapped in snares set for furbearing mammals, which use raw meat as bait (Slaght and Surmach 2008).
These owls are primarily active at dusk and dawn. During the brood-rearing season, these owls are most often seen active during the day. For an owl, it spends unusual amounts of time on the ground. Early reports of concentrations of as many as 5-6 owls near rapids and non-freezing springs are dubious records, as these owls are highly territorial (Slaght and Surmach 2008).
Breeding and Status
This bird does not breed every year due to fluctuations in food supply and conditions. Laying of eggs begins as early as mid-March, when ground and trees are still covered with snow. These owls prefer nesting in hollow tree cavities in Japan (Takenaka 1998) and Russia (Slaght and Sumrach 2008). Reports of nesting on fallen tree trunks and on the forest floor are very rare occurrences at best, but possibly untrue. Other than nest cavities, there are very isolated records of nesting on cliff shelves and in old black kiteBlack Kite
The Black Kite is a medium-sized bird of prey in the family Accipitridae, which also includes many other diurnal raptors. Unlike others of the group, they are opportunistic hunters and are more likely to scavenge. They spend a lot of time soaring and gliding in thermals in search of food. Their...
nests (Takenaka 1998, Yamamoto 1999). Nest cavities have to be quite large in order to accommodate these birds. Clutch size is 1 to 3, usually 2 (Yamamoto 1999). In Russia, clutches are usually just one egg (Slaght and Surmach 2008). Eggs are 6.2 cm (2.5 in) long and 4.9 cm (1.9 in) wide. The males provide food for the incubating female and later the nestlings. The incubation period is about 35 days and young leave the nest within 35–40 days but are often fed and cared for by their parents for several more months. Juveniles linger on their parents' territory for up to two years before dispersing to find their own territory. Once full-sized, these owls have few natural predators. There is one record of an adult fish owl being stalked and killed by a Eurasian lynx
Eurasian Lynx
The Eurasian lynx is a medium-sized cat native to European and Siberian forests, South Asia and East Asia. It is also known as the European lynx, common lynx, the northern lynx, and the Siberian or Russian lynx...
in Russia, while the owl hunted along a river bank (Yelsukov 2005, cited in Slaght and Surmach 2008).
The Blakiston's Fish Owl is endangered due to the widespread loss of riverine forest, increasing development along rivers and dam construction. The current population in Japan is approximately 100-150 birds (20 breeding pairs and unpaired individuals), whereas on mainland Asia the population is higher, variously estimated at several hundred or perhaps thousands of individuals (Slaght and Surmach 2008). In Russia, fish owls are killed by fur-trappers (see above), drown in nets set for salmon, and are shot by hunters (Slaght and Surmach 2008). In Japan, death by hunting is unlikely, but fish owls have been hit and killed by cars (Yanagawa 1993). Local conservation efforts in Japan have been undertaken including education and installation of large nest-boxes.
Henry Seebohm named this bird after the English naturalist Thomas Blakiston
Thomas Blakiston
Thomas Wright Blakiston was an English explorer and naturalist.Born in Lymington, Hampshire, England, Blakiston was the son of Major John Blakiston, second son of Sir Matthew Blakiston, 2nd Baronet...
, who collected the original specimen in Hakodate on Hokkaidō
Hokkaido
, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island; it is also the largest and northernmost of Japan's 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaido from Honshu, although the two islands are connected by the underwater railway Seikan Tunnel...
, Japan in 1883.
Importance in Indigenous Cultures
Blakiston's fish owl is revered by the AinuAinu people
The , also called Aynu, Aino , and in historical texts Ezo , are indigenous people or groups in Japan and Russia. Historically they spoke the Ainu language and related varieties and lived in Hokkaidō, the Kuril Islands, and much of Sakhalin...
peoples of Hokkaido, Japan as a Kamuy (divine being) called Kotan koru Kamuy (God that Protects the Village). In Russia, the species is currently considered a food source by the Evens
Evens
The Evens or Eveny are a people in Siberia and the Russian Far East. They live in some of the regions of the Magadan Oblast and Kamchatka Krai and northern parts of Sakha east of the Lena River. According to the 2002 census, there were 19,071 Evens in Russia...
people in northern Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
and the northern Russian Far East
Russian Far East
Russian Far East is a term that refers to the Russian part of the Far East, i.e., extreme east parts of Russia, between Lake Baikal in Eastern Siberia and the Pacific Ocean...
. Previously, fish owls were hunted as a food source by the Udege
Udege
Udege are a people who live in the Primorsky Krai and Khabarovsk Krai regions in Russia. They live along the tributaries of the Ussuri, Amur, Kungari and Anyuy Rivers. The Udege speak the Udege language, which belongs to the Tungusic language family...
peoples in Primorye
Primorye
Primorye is the name of several inhabited localities in Russia:*Primorye, Kaliningrad Oblast, an urban locality in Svetlogorsky District of Kaliningrad Oblast...
, but this practice has fallen out of favor in recent times (Slaght and Surmach 2008).