Blakiston's fish owl

Bubo blakistoni.jpg
Blakiston's fish owl (Bubo blakistoni), the largest living species of owl, is a fish owl, a sub-group of eagle owls which specialize in hunting in riparian areas. This species is a part of the family known as typical owls (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 of the two genus names is applied for this species. Its habitat is riparian forest, with large, old trees for nest-sites, near lakes, rivers, springs and shoals that don't freeze in winter. Henry Seebohm named this bird after the English naturalist Thomas Blakiston, who collected the original specimen in Hakodate on Hokkaidō, Japan in 1883.

It is more correct to call this species the Blakiston's eagle owl. This is because it is more closely related to the Eurasian eagle-owl by studies of the main subgenus of the species, B. b. dumeril, than to the subgenus of fish owls that it was believed to be more close to, i.e. Ketupu. This was proven by osteological (skeleton/bone-related) and DNA-based tests in 2003 by ornithologists/taxonomists Michael Wink and Claus König, author of Owls of the World. However, the other fish owls are not believed to be divergent enough to support a separate genus either and now all fish owls are generally also included in the Bubo genus. Given that it shares genetic material osteological characteristics with the eagle-owl and also seems to share some characteristics with the other three fish owls (especially the brown species), the place of the Blakiston's fish owls in this evolutionary chain is ambiguous. Some authors have wondered whether the Blakiston's represents an intermediate step between traditional eagle-owls and the other fish owls, despite the current gap in distribution between Blakiston's and other fish owls. Whether other Asian eagle-owls with sideways slanting ear-tufts, namely the spot-bellied (B. nipalensis), the barred (B. sumatranus) and especially the somewhat superficially fish owl-like dusky eagle-owl (B. coromandus) are closely related to the fish owls and/or the Blakiston's is also unclear. Despite a few authors also include them in Bubo, the fishing owls of Africa, generally classified in the genus Scotopelia, seem to be unrelated in every major way, based on external characteristics, oseology and preliminary genetic materials, to the fish owls and it is unclear how, and if, they are related to typical eagle-owls.

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 males and 3.25 kg (7.2 lb) in 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 the three major categories: weight, length, 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. 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.




This page was last edited on 17 February 2018, at 09:22.
Reference: under CC BY-SA license.

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