Tawny owls are monogamous and territorial year around. Young birds select territories and look for mates in autumn and tend to be very vocal, especially males. Due to their highly territorial behaviour, young birds frequently struggle to establish a territory unless a nearby adult dies. Males routinely engage in territorial fights.Hume, R. (1991). Owls of the world. Running Press, Philadelphia. Territories have been known to have been maintained by single tawnys for up to 10 years in Russia and 13 years in Berlin.Dementiev, G. P., Gladkov, N. A., Ptushenko, E. S., Spangenberg, E. P., & Sudilovskaya, A. M. (1966). Birds of the Soviet Union, vol. 1. Israel Program for Scientific Translations, Jerusalem.Wendland, V. (1963). Fünfjährige Beobachtungen an einer Population des Waldkauzes (Strix aluco) im Berliner Grunewald. Journal für Ornithologie, 104(1), 23–57. Of 34 males in Wytham, only one male moved off of territory, due to being disturbed by humans.Hirons, G.J.R. (1976). A population study of the Tawny Owl Strix aluco) and its main prey species in woodland. D. Phil Thesis, University of Oxford. It appears to be largely up to the male to select territorial boundaries. Despite the aforementioned territorial behaviour, active nests of two separate pairs at as close as , in the Tegel forest, have been reported. This species shows very little extrapair parentage.Saurola, P. (1987). Mate and nest-site fidelity in Ural and Tawny owls. Biology and conservation of northern forest owls, 81–86. In Switzerland for example, a study of 137 nestings found that only one, or 0.7%, were from a different father than the mate, females cannot generally raise young without male contribution so the pair structure of these highly residential owls insures little instance of cuckoldry.Saladin, V., Ritschard, M., Roulin, A., Bize, P., & Richner, H. (2007). Analysis of genetic parentage in the tawny owl (Strix aluco) reveals extra-pair paternity is low. Journal of Ornithology, 148(1), 113–116. Cases of bigamy were reported at Wytham in 6 of 34 males, in situations where apparently a neighboring male died and was suffixed subsequently, however, one or the other nesting attempts would completely fail each time.Hirons, G. J. M. (1985). The effects of territorial behaviour on the stability and dispersion of tawny owl (Strix aluco) populations. Journal of Zoology, 1(1), 21–48. In Pavia, 3 of 22 territories included two mature females.Galeotti, P. (1998). Correlates of hoot rate and structure in male Tawny Owls Strix aluco: implications for male rivalry and female mate choice. Journal of Avian Biology, 29, 25–32.
Nests The male advertises several potential nest sites to his mate by singing at the entrance, slipping inside and so on, with the female finally selecting one. The typical nest site of a tawny owl is a tree hollow, wherein the owls will nest directly on the interior hole's surface. Tree hollows used may be as much as above the ground, but are usually within about of the ground.Galeotti, P. (2001). Strix aluco Tawny Owl. Birds of Western Palearctic. Update, 3(1), 43–77. Virtually any species of deciduous tree may be used provided holes are available. These tree cavities may be of any origin, with trees that grow large such as oak, beech, poplar, maple, lime, hornbeam and alder often regularly utilized.Wiącek, J., Polak, M., & Grzywaczewski, G. (2010). The role of forest age, habitat quality, food resources and weather conditions for Tawny Owl Strix aluco populations. Polish Journal of Environmental Studies, 19(5), 1039–1043.Camprodon, J., Salvanyà, J., & Soler-Zurita, J. (2008). The abundance and suitability of tree cavities and their impact on hole-nesting bird populations in beech forests of NE Iberian Peninsula. Acta Ornithologica, 43(1), 17–31.Salvati, L., Manganaro, A., & Ranazzi, L. (2002). Wood quality and the Tawny Owl Strix aluco in different forest types of central Italy. Ornis Svecica, 12, 47–51.Jedrzejewski, W., Jedrzejewska, B., Szymura, A., & Zub, K. (1996). Tawny owl (Strix aluco) predation in a pristine deciduous forest (Bialowieza National Park, Poland). Journal of animal ecology, 105–120. Female may scratch out a shallow base in soil if present and sometimes seen to reportedly tear eggs into pieces as a cushion from their broods. Other tree nest locations have included those on top of a Witch's broom and on top of the tree canopy.Mebs, T. (1980). Eulen und Käuze. Stuggart. Natural holes in trees are often the most frequently used nesting site, followed closely in recent decades many artificial nest boxes, preferably those with a entrance or larger.Gryz, J., & Krauze-Gryz, D. (2011). Wykorzystanie skrzynek lęgowych przez puszczyki Strix aluco w środkowej Polsce. Studia i Materiały Centrum Edukacji Przyrodniczo-Leśnej, 13(2 ). Of the nest boxes erected in different parts from Kielder forest and the Glenbranter forest of Argyll, 592 nest boxes were placed at high along the side of trees and 17.4% of which were used by tawnys (in latter 2 years of study up to 24.1%).Petty, S. J. (1987). The design and use of a nestbox for Tawny Owls Strix aluco in upland forests. Quarterly Journal of Forestry, 81, 103–109. In southeastern Scotland, all nest boxes erected in habitat were eventually utilized by tawny owls.Petty, S. J., Shaw, G., & Anderson, D. I. K. (1994). Value of nest boxes for population studies and conservation of owls in coniferous forests in Britain. Journal of Raptor Research, 28(3), 134–142. Many nest boxes were recorded to be used as roost sites in the Milan, with only 12.3% of the 44% of nest boxes actually used by owls for breeding, usually with the owls utilizing boxes that were at least above the ground.Sacchi, R., Galeotti, P., Boccola, S., & Baccalini, F. (2004). Occupancy rate and habitat variables influencing nest-box use by tawny owls Strix aluco. AVOCETTA-PARMA-, 28(1), 25–30. Nest boxes are most successful wherever natural tree cavities are scarce or absent, such as conifer forests, young successional woods and farmlands.Petty, S. J. (1992). Ecology of the tawny owl Strix aluco in the spruce forests of Northumberland and Argyll (Doctoral dissertation, The Open University).Saurola>Saurola, P. (1987). Mate and nest-site fidelity in Ural and Tawny owls. Biology and conservation of northern forest owls, 81–86.Plesnik, J., & Dusik, M. (1994). Reproductive output of the Tawny Owl Strix aluco in relation to small mammal dynamics in intensively cultivated farmland. Meyburg B.-U. & RD Chancellor (eds.). Raptor Conservation Today. World Working Group on Birds of Prey and Owls & Pica Press, London: 531, 535. Tawny owls may not infrequently nest in an unmodified black woodpecker hole.Wille, H. G. (1972). Ergebnisse einer mehrjährigen Studie an einer Population des Waldkauzes (Strix aluco) in West-Berlin. Orn. Min. 24: 3, 7. This species may too nest in nest of larger birds such as crows, common ravens (Corvus corax) and Eurasian magpies as well as common buzzards, black kites, northern goshawks and various eagles while the sometimes recorded as used smaller nests such as those of Eurasian jays, Eurasian sparrowhawks and common wood pigeons but these are at potential risk of collapse. Occasionally, tawny owls have also been recorded nesting in abandoned burrows of larger mammals (e.g. red fox and European badger (Meles meles) as well as those of rabbits). Other nesting locations recorded for the species have included bare cliff ledges, between the roots of heavy tree trunks, on the bare forest floor and among heather. Also rarer still nests have been reported in the recesses of stone walls, in chimneys of large buildings, on cabins and sheds, in dovecotes and church towers. In southern Finland, 95% of 123 nest boxes put out were occupied by tawny owls in 1970–1975, natural tree hole use decreased in same period from 48% to 3%, on top of stumps from 4% to 1% and in buildings from 15% to 1%.Mikkola, H. (1983). Owls of Europe. T. & AD Poyser.
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