Blakiston's Fish Owl
A species of Horned Owls Scientific name : Bubo blakistoni Genus : Horned Owls
Blakiston's Fish Owl, A species of Horned Owls
Botanical name: Bubo blakistoni
Genus: Horned Owls
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Description General Info
Photo By Ayuwat Jearwattanakanok
Description
Blakiston's fish owl is the largest living species of owl. A pair field study of the species showed males weighing from 2.95 to 3.6 kg (6.5 to 7.9 lb), while the female, at up to 2.95 to 4.6 kg (6.5 to 10.1 lb), is about 25% larger. Around February, the average weight of Russian fish owls was 3.1 kg (6.8 lb) in seven males and 3.25 kg (7.2 lb) in five females, typically when their body mass at its lowest throughout the year. Blakiston's fish owl measures 60 to 72 cm (24 to 28 in) in total length, and thus measures slightly less at average and maximum length than the great gray owl (Strix nebulosa), a species which has a significantly lower body mass. The Eurasian eagle-owl (B. bubo) is sometimes considered the largest overall living owl species. The three largest races of eagle-owl, all found in Siberia and the Russian Far East, are close in size to the Blakiston's fish owl. According to Heimo Mikkola, the very largest specimen of eagle-owl was 30 mm (1.2 in) longer in bill-to-tail length than the longest Blakiston's fish owl, while the top weight of the two species is exactly the same. The longest great gray owl was 120 mm (4.7 in) longer than the biggest Blakiston's fish owl but would be about 2.5 times lighter than the weight of the largest female Blakiston's. However, the average measurements of Blakiston's fish owl surpass the average measurements of the Eurasian eagle-owl in at least two of the major categories: weight and wingspan, making Blakiston's the overall largest species of owl. Even the large Siberian races of eagle-owl are slightly smaller on average than the Blakiston's, at least in terms of body mass and wing size. In the largest known body mass cited for a Eurasian eagle-owl population, the weights cited, for instance, were a mean 2.42 kg (5.3 lb) for the males and a mean of 3.164 kg (6.98 lb). The maximum wingspan of the Blakiston's fish owl is also greater than any known eagle-owl. The wingspan range known for Blakiston's fish owls is 178 to 190 cm (5 ft 10 in to 6 ft 3 in). It is possible the largest specimens can attain a wingspan of approximately 200 cm (6 ft 7 in). The Blakiston's is noticeably larger than the other three extant species of fish owl. In terms of structure, the Blakiston's fish owl is more similar to eagle-owls than it is to other fish owls but it shares a few characteristics with both types of owl. Like all fish owls, its bill is relatively long, the body relatively husky and wings are relatively long compared to eagle-owls. It also shares with other fish owls a comparatively long tarsi, although relative to their size the three smaller fish owl have a proportionately longer tarsus. Other than these few characteristics, a Blakiston's fish owl skull and skeleton is practically the same as that of a Eurasian eagle-owl. The talons of the Blakiston's fish owl are similar in shape and size to those of the Eurasian eagle-owls. It has been stated that the combination of wavy cross patterns on the underside of the Blakiston's plumage and its huge talons make it look strikingly like an outsized great horned owl (B. virginianus) from below. Two external characteristics that Blakiston's share with eagle-owls, but not with the other fish owls, is that its tarsi are totally feathered and that its wing beats are silent, although apparently the Blakiston's has relatively fewer sound-blocking combs on its wing primaries than the a comparable eagle-owl would. Among standard measurements, which at average and maximum are greater than any other living owl other than tail length, the wing chord measures 447–560 mm (17.6–22.0 in), the tail measures 243–305 mm (9.6–12.0 in), the tarsus is 73–102 mm (2.9–4.0 in) and the culmen is around 55 to 71 mm (2.2 to 2.8 in). Superficially, this owl somewhat resembles the Eurasian eagle-owl but is paler and has relatively broad and ragged ear tufts which hang slightly to the side. The upperparts are buff-brown and heavily streaked with darker brown coloration. The underparts are a paler buffish brown and less heavily streaked. The throat is white. The iris is yellow (whereas the Eurasian eagle-owl typically has an orange iris). The Eurasian eagle-owl and Blakiston's fish owl both occur in the Russian Far East and are potentially could compete for resources, although no scientifically observed interactions of any kind have been reported between these two largest owl species. It is likely, given the sizeable gap between the dietary preferences of the species (mainly aquatic animals in the Blakiston's, mainly upland, terrestrial species in the eagle-owl) that competition for food is not normally a serious problem. Identification of the Blakiston's from other fish owls is not an issue as there is a gap of distribution of approximately 800 km (500 mi) between the ranges of the Blakiston's and the tawny fish owl (B. flavipes) and about 2,000 km (1,200 mi) separates the range of the Blakiston's and the brown fish owl (B. zeylonensis). Improbably, early naturalist thought that the Blakiston's and brown fish owls belonged to the same species. The streaking on the underside of the Brown and Blakiston's are similar and their songs sound more similar to each other than they do with the two songs of the other two species of fish owl. Vocalizations differ among the recognized subspecies. In the nominate subspecies from Japan, the male calls twice and the female responds with one note, whereas the mainland subspecies has a somewhat more elaborate, four-note duet: HOO-hoo, HOOO-hoooo (here, the male call is in capital letters (HOO) and the female call in lower case (hoo)). The transliterations of the calls of owls from Russia, representative of the owl's vocal variations, are SHOO-boo and FOO-foo-foo. The territorial song or call in Russia in particular has been described as somewhat like a short, deep eagle-owl's call. Despite its slightly larger size, the Blakiston's fish owls voice is not as sonorous or as far-carrying as is the Eurasian eagle-owl's voice is. The fish owl's voice is rather deeper, however. As in most owls, vocal activity tends to peak directly before nesting activity begins, so peaks around February in this species. This duet of pairs of Blakiston's fish owl in the period leading up the breeding season is so synchronized that those unfamiliar with the call often think it is only one bird calling. When an individual bird calls, it may sound like hoo-hooo. Juveniles have a characteristic shriek, typically a startling and slurred phee-phee-phee.
Size
72 cm
Feeding Habits
Blakiston's Fish Owl primarily consumes various aquatic prey, including fish like pike, catfish, and salmon. They exhibit sexual dimorphism in prey selection – males often catch frogs and smaller fish, while females target larger fish. Blakiston's Fish Owl hunt by wading in shallows or perching by rivers, snatching prey with their feet. They are active at dawn and dusk and may hunt or brood during daylight in the breeding season. Blakiston's Fish Owl also feed on mammals, large birds, and occasional carrion.
Habitat
Blakiston's Fish Owl is typically found in dense old-growth forests, mainly near rivers or coastlines that offer open water during frigid northern winters. These birds inhabit regions with broadleaf or mixed forests alongside clear rivers or taiga rivers that don't fully freeze. They have a proclivity for tributary confluences with slow-flowing channels and steep-sided wooded valleys near swift rivers. Habitats with large trees and riparian old-growth are preferred for nesting and foraging, as these environments support an abundance of salmonid prey required for their sustenance.
Dite type
Carnivorous
General Info
Species Status
Blakiston's fish owl is classified as an Endangered Species by the IUCN. It is endangered due to the widespread loss of riverine forest, increasing land development along rivers and dam construction. The current population in Japan has been estimated at approximately 100-150 birds (20 breeding pairs and unpaired individuals), whereas on mainland Asia the population is higher, at times variously estimated at several hundred or perhaps up to thousands of individuals. Globally and included more recent detailed analysis from Russia, it is estimated that the population consists in total consists of about 1,000-1,500 individuals, or about 500-850 pairs. In the Primorye, it is estimated that 200 to 400 individuals remain. In Russia, fish owls are killed by fur-trappers (see above), drown in nets set for salmon, and are shot by hunters. In Japan, death by hunting is unlikely, but fish owls have been hit by cars and killed by power lines. Additionally, cases of 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. Given their very small global population, ongoing deaths are unlikely to be sustainable. Local conservation efforts in Japan have been undertaken including education, installation of large nest-boxes and supplemental feeding. Biologists have found the presence of Blakiston's fish owls as good indicators of the health and disturbance level of a forest and of fish populations. An additional concern was a clear lack of genetic diversity found in Russia's fish owls upon the testing of their genome, with similar concerns expressed in Japan as well as evidence of inbreeding. Evidence has been found of a gradual recovery of the Blakiston's fish owl population in Hokkaido but Japanese conservationists are vexed by the lack of suitable habitat and recommend land use changes to encourage the growth of the population.
Photo By Ayuwat Jearwattanakanok
Scientific Classification
Phylum
Chordates Class
Birds Order
Owls Family
True owls Genus
Horned Owls Species
Blakiston's Fish Owl