The Ural owl (Strix uralensis) is a large nocturnal owl. It is a member of the true owl family, Strigidae. The Ural owl is a member of the genus Strix, that is also the origin of the family's name under Linnaean taxonomy.Sclater, P. L. (1879). Remarks on the Nomenclature of the British Owls, and on the Arrangement of the Order Striges. Ibis, 21(3), 346-352. Both its common name and scientific name refer to the Ural Mountains of Russia where the type specimen was collected. However, this species has an extremely broad distribution that extends as far west as much of Scandinavia, montane eastern Europe, and, sporadically, central Europe, thence sweeping across the Palearctic broadly through Russia to as far east as Sakhalin and throughout Japan.Voous, K.H. (1988). Owls of the Northern Hemisphere. The MIT Press, . The Ural owl may include up to 15 subspecies, but most likely the number may be slightly fewer if accounting for clinal variations.
This forest owl is typical associated with the vast taiga forest in Eurosiberia, although it ranges to other forest types, including mixed forests and temperate deciduous forest.Tutiš, V., Radović, D., Ćiković, D., Barišić, S., & Kralj, J. (2009). Distribution, density and habitat relationships of the Ural owl Strix uralensis macroura in Croatia. Ardea, 97(4), 563-571. The Ural owl is something of a dietary generalist like many members of the Strix genus, but it is usually locally reliant on small mammals, especially small rodents such as voles.Obuch, J., Danko, Š., Mihók, J., Karaska, D., & Šimák, L. (2014). Diet of the Ural owl (Strix uralensis) in Slovakia. Slovak Raptor Journal, 7, 59-71. In terms of its reproductive habits, Ural owls tend to vigorously protect a set territory on which they have historically nested on a variety of natural nest sites, including tree cavities and stumps and nests originally built by other birds but now, in many parts of the range are adapted to nest boxes made by biologists and conservationists.Hume, R. (1991). Owls of the world. Running Press, Philadelphia.Vazhov S.V., Bakhtin R.F. & Vazhov V.M. (2016). On the Use of Nest Boxes for Study the Ecology of Strix uralensis. International Journal of Applied and Basic Research, 333: 498-498 Breeding success is often strongly correlated with prey populations.Brommer, J. E., Pietiäinen, H., & Kolunen, H. (2002). Reproduction and survival in a variable environment: Ural owls (Strix uralensis) and the three-year vole cycle. The Auk, 119(2), 544-550. The Ural owl is considered to be a stable bird species overall, with a conservation status per the IUCN as a least concern species. Despite some local decreases and extinctions, the Ural owl has been aided in central Europe by reintroductions.Scherzinger, W. (2006). Die Wiederbegründung des Habichtskauz-Vorkommens Strix uralensis im Böhmerwald. Zeitschrift bayerischer und baden-württembergischer Ornithologen, 45(2/3).
Description
Like most Strix species, it has a broad, rounded head with a correspondingly round facial disc, barring a tiny V-shaped indentation. The Ural owl has, for an owl, an exceptionally long tail that bears a wedge-shaped tip. In colour, it tends to be a plain pale greyish-brown to whitish overall (with more detailed description of their variation under subspecies), with a slightly darker grey-brown to brown back and mantle with contrasting whitish markings. The underparts are pale cream-ochre to grey-brown and are boldly (though sometimes more subtly) overlaid with dark brown streaking, without crossbars. Many variations are known in overall plumage colour both at the subspecies level and the individual level. However, the Ural owl usually appears as a rather pale grey-brown owl, usually lacking in the warmer, richer colour tones of many other Strix owls, with distinct streaking below. In flight, a Ural owl shows a largely buffish-white underwing marked with heavy dark bars around the trailing edge and tip, while the long white tipped tail often appears slung downwards. Their flight style is reminiscent of a buzzard, but with deeper, more relaxed wing beats, with their style of flight often giving the appearance of quite a large bird. The eyes are dark brown, being relatively small and closely set to each other, which is opined to give them a less "fierce" countenance than that of a great grey owl (Strix nebulosa). The eyes are reminiscent of an almond in both shape and colour. The bill is yellowish, with a dirty yellow cere. Meanwhile, the tarsi and toes are covered in greyish feathering and the talons are yellowish brown with darker tips.
The Ural owl is a rather large species. Full-grown specimens range in total length from , which may render them as roughly the eight longest owl species in the world (though many owls are heavier on average).Brazil, M. (2018). Birds of Japan. Bloomsbury Publishing.Owls of the World: A Photographic Guide by Mikkola, H. Firefly Books (2012), Sylvén, A. (1907). Jakten i vårt land. P.A. Norstedt & söners förlag. Wingspan can vary in the species from . Like most birds of prey, the Ural owl displays reverse sexual dimorphism in size, with the female averaging slightly larger than the male. Reportedly talon size and body mass is the best way to distinguish the two sexes of Ural owl other than behavioral dichotomy based on observations in Finland.Kivelä, J. (2011). Studying and Trapping the Breeding Ural Owls in the Western Part of Finland. Raptors Conservation, (21). Weight is variable through the European part of the range. Males have been known to weigh from and females have been known to weigh from .CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), . Voous estimated the typical weight of males and females at and , respectively. It is one of the larger species in the Strix genus, being about 25% smaller overall than the great grey owl, the latter certainly being the largest of extant Strix species in every method of measurement. Body masses reported for some of the more southerly Asian species such as brown wood owl (S. leptogrammica) and spotted wood owl (S. seloputo) (as well as the similarly sized but unweighed mottled wood owl (S. ocellata)) show that they broadly overlap in body mass with the Ural owl or are even somewhat heavier typically despite being somewhat smaller in length, being somewhat stockier in build yet shorter tailed than the Ural owl.Holt, D.W., Berkley, R., Deppe, C., Enríquez Rocha, P., Petersen, J.L., Rangel Salazar, J.L., Segars, K.P., Wood, K.L. & Marks, J.S. (2019). Typical Owls. In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. Despite having no published weights for adults, Père David's owl (S. davidi) seems to also be of a similar size to the Ural owl as well.Scherzinger, W., Fang, Y., Sun, Y. H., & Klaus, S. (2014). Revised description of Pere David's Owl Strix davidi based on field observations in Central China. Ornithol. Anz., 53: 54–93. Among standard measurements, in both sexes, wing chord can measure from across the range and tail length can from . Among extant owls, only the great grey owl is certain to have a longer tail. Though less frequently measured, the tarsus may range from and, in northern Europe, the total bill length measured from .Momiyama, T. T. (1928). New and known forms of the Ural Owl (Strix uralensis) from southeastern Siberia, Manchuria, Korea, Sakhalin and Japan. The Auk, 177-185.Buturlin, S.A. (1907). Die paläarktischen Formen vor Syrnium Savign. Journal für Ornithologie, 55: 332-336. The foot span can regularly reach around in full-grown owls.
Vocalizations and ear morphology
The song of the male is a deep rhythmic series of notes with a short pause after the first two notes, variously transcribed as wohu... huw-huhuwo or huow-huow-huow. The phrase repeats at intervals of several seconds. The male's song may carry up to to human perception but usually is considered not quite that far-carrying.Lundberg, A. (1980). Vocalizations and courtship feeding of the Ural Owl Strix uralensis. Ornis Scandinavica, 65-70. Peak singing times in Finland during springtime are 10 pm-12 am and more intensely at 1-3 am, which differed from the peak times for nest visits.Korpimäki, E., & Huhtala, K. (1986). Nest visit frequencies and activity patterns of Ural Owls Strix uralensis. Ornis Fennica, 63(2), 42-46. The female has a similar but hoarser and slightly higher pitched song, giving it a more "barking" quality. Not infrequently, Ural owls will duet during courtship. In addition, a deep, hoarse heron-like kuwat or korrwick is probably used as a contact call. These are more elongated and harsher than the kewick note made by tawny owls (S. aluco). Young beg with hoarse chrrreh calls, again similar to the ones by young tawny owls but deeper. Vocal behavior tends to peak in early spring until the young leave the nest, most often during incubation and nesting in the form of prey delivery countercalling. The alarm call, which is typically delivered during territorial rounds, of the male is coincidentally analogous to the territorial song of the short-eared owl (Asio flammeus), which is considered a somewhat hollow sounding hoot. The alarm call is audible at up to away. The Ural owl also has a particularly menacing bill-snapping display.Otto-Sprunck, A. (1967). Übersprungsschaffen beim Habichtskauz (Strix uralensis). Ornis Fenn. 44: 78. In total, Swedish biologist reported that about nine different calls were uttered by Ural owls.Lindblad, J. (1967). I ugglemarker. Stockholm.Holmberg, T. (1974). En studie av slagugglans Strix uralensis liten. Vr Fdgelv, 33, 140-146.Scherzinger, W. (1980). Zur Ethologie der Fortpflanzung und Jugendentwicklung des Habichtkauzes (Strix uralensis) mit Vergleichen zum Waldkauz (Strix aluco). Bonn. Zool. Mongr, 15. Despite the range of calls, the species is generally very quiet for a large owl and may not vocalize even at peak times for perhaps up to nearly 2 days.
The ears of the Ural owl are quite large, averaging about on the left and on the right with the pre-aural dermal flap measuring about . In fact their ears are amongst the largest recorded in owls.Kelso, L. (1940). Variation of the external ear-opening in the Strigidae. The Wilson Bulletin, 24-29.Voous, K. H. (1964). Wood owls of the genera Strix and Ciccaba. Zoologische Mededelingen, 39(46), 471-478. In combination with their large ears, the well-developed facial disc shows the importance of sound to hunting to this and other owl who hunt in boreal zones. While the Ural owl was found to be aurally overdeveloped compared to other Strix such as the barred owl (S. varia) it was found to be underdeveloped in comparison to owls more confined to true boreal type habitats, like the great grey owl and the boreal owl (Aegolius funereus).Mikkola, H. (1983). Owls of Europe. T. & AD Poyser.
Confusion with similar owl species