Tawny Owl (Strix aluco) Predation in a Pristine Deciduous Forest (Bialowieza National Park, Poland)

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Tawny owl Strix aluco predation on its main prey (bank voles Clethrionomys glareolus and yellow-necked mice Apodemusflavicollis) and alternative prey (shrews, birds, and amphibians) was studied in the pristine deciduous forests of eastern Poland during a 7-year period (1985/86-1991/92) that included 5 years of moderate densities of rodents and 2 years of outbreak and crash triggered by a heavy seed crop of oak, hornbeam, and maple. 2. Number of resident owls was rather stable; 45-53 owls per 10km2 in years of moderate and high rodent numbers, and 33 owls per 10km2 in a rodent crash year. Numerical response of owls to rodent densities was log shaped. 3. In the cold season, the dietary (functional) response of owls to autumn density of rodents was of type II (logarithmic). No functional response of owls was observed to shrew numbers. Owl hunting rate on amphibians in winter was shaped by the mean temperature of the cold season and, to a lesser extent, by availability of rodents. Owl hunting rate on birds was inversely related to rodent abundance. 4. During the seven cold seasons (1 October-15 April), tawny owls removed 3-19 mice, 2-18 voles, 2-7 shrews, 0-2 birds, and 1-9 frogs from an average hectare of the forest. Total predation on rodents (N prey removed ha-1) was lowest during the crash of rodents and highest during the outbreak; it grew logarithmically with increasing density of rodents. On average, in the cold season, tawny owls removed 54% of autumn numbers of mice and 40% of those of bank voles. Percentage predation peaked at 22 rodents ha-l in autumn. At both higher and lower prey densities, percentage predation declined. 5. The percentage predation curve of tawny owl was compared to the frequency distribution of autumn densities of rodents in Bialowieza (from 23-year trapping). The heaviest predation fell to prey densities that occurred most frequently. 6. In summer seasons (July-September 1988-92), tawny owls (both adults and juveniles) consumed 0-5-19 mice and 0-4-10 voles from an average hectare. Percentage predation varied from 6% to 74% of rodent numbers recorded in July, but rodents bred rapidly and recruitment usually more than compensated for losses due to predation. 7. Total predation by tawny owls on rodents was quite stable as a consequence of high stability of owl numbers. Percentage predation, although heavy in all years except for rodent outbreak, was not density-dependent and therefore tawny owls did not regulate rodent numbers. In the deciduous forests of Bialowieza National Park, the pattern of predation by tawny owl, a ...

Barn OwlTyto albaPredation on Small Mammals in Relation to the Mediterranean Environment (Pisa Province, Italy)

“…The high proportion of shrews in its diet suggests that this species is a non-selective small mammal predator, especially if compared with the Long-eared Owl Asio otus and the Tawny Owl Strix aluco (Mikkola 1983, Riga & Capizzi 1999, Capizzi 2000. In addition, these species are known to be selective towards age and sex classes of its small mammal prey (Saint Girons 1973, Jędrzejewski et al 1996, Zalewski 1996. Therefore, basing on the assumption that the Barn Owl forages on the prey in relation to its availability, studies on the composition of small mammal assemblages are frequently done by investigating Barn Owl diet.…”

Diet shifts of the tawny owl Strix aluco in central and northern Italy

“…The feeding ecology of tawny owl, including seasonal variation, has been studied in a number of European countries (e.g., Uttendorfer, 1952;Southern, 1969;Jedrzejewski et al, 1996). In Italy, it feeds upon mammals ranging in size from shrews to rabbits: for this reason, the mean size of its prey varies markedly from one locality to another.…”

“…The tawny owl, Strix aluco, is a widespread resident present in a large variety of habitats, ranging from ancient woodland and open farmland to urban areas (e.g., Contoli & Sammuri, 1978;Galeotti, 1994;Redpath, 1995;Jedrzejewski et al, 1996). It is generally considered a typical woodland owl, as morphological characteristics (e.g., short and broad wings, short tail) enable it to manoeuvre among tree branches and thick foliage (Mikkola, 1983).…”

Seasonal and habitat variation in the diet of the tawny owl (Strix aluco) in central Poland during unusually warm years

“…It has been shown that the composition of the tawny owl's diet changes significantly in severe winter conditions (Jędrzejewski et al 1994(Jędrzejewski et al , 1996 and mild winters may increase the number of breeding owls and their reproductive performance (Sasvári & Hegyi 2002;Solonen 2005). Moreover, the tawny owl's winter mortality is correlated with weather severity (Jędrzejewska & Jędrzejewski 1998).…”