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.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. 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 (Strix 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). Confusion with similar owl species The Ural owl is a fairly distinctive looking bird but can be confused for other owls, especially with others in the Strix genus.Wardhaugh, A. A. (1983). Owls of Britain and Europe. Blanford. The tawny owl is much smaller with a conspicuously shorter tail and a relatively larger head. The tawny species, which occurs variously in grey, brown and red morphs, has underparts with dark shaft-streaks and crossbars, as opposed to the heavy but straight streaking of the Ural owl. The great grey owl is larger than the Ural owl with a huge head and relatively even smaller yellow eyes while their facial disc has strong concentric lines. In colour, the great grey is distinctly more solidly uniform and somewhat dark greyish than the Ural owl. An unlikely species to mistake a Ural owl is the Eurasian eagle-owl (Bubo bubo) which is much larger (by a considerable margin the heaviest and longest winged owl in Europe) with prominent ear tufts, a squarish (not rounded) head shape and orange eyes as well as with distinctly different markings. Long-eared owls (Asio otus) are