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Diet of adult eagle uwl during breeding season in Northwestern Türkiye

Gözütok Serdar

Polish Journal of Ecology

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2023

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Vol. 71, nr 1

27--36

EN

Published studies on the diet of the Eurasian eagle owl (Bubo bubo) in Türkiye are limited to the eastern and central parts of the country. This study presents the diet composition of a single pair of eagle owl in the breeding season in Northwestern Türkiye. In total, 91 pellets of B. bubo were collected in Bolu Province. They contained 949 prey items of 18 prey species belonging to the orders Rodentia, Eulipotyphla, and Carnivora, class Mammalia and eight species belonging to the order Passeriformes, class Aves. The owl's diet was mostly composed of rodents (94.62%). Microtus hartingi, Microtus subterraneus, and Sciurus anomalus were detected in the diet of Bubo bubo in Türkiye for the first time. In addition, a specimen of Mustela nivalis was recorded in Bubo bubo pellets for the first time in Northwestern Türkiye. Niche breadth, Shannon-Wiener, and Simpson indices were calculated and found to be 6.69, 2.23, and 0.85 respectively. The estimated species richness (Chao1) of eagle owl prey was 30.9. The average prey number per pellet was 10.42 ± 5.76. The predominant species in the diet of Bubo bubo were Microtus mystacinus, Cricetulus migratorius, and Microtus subterraneus. Detailed comparison with other eagle owl prey data collected across Türkiye is also presented.

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Predation and the dynamics of the bank vole, Clethrionomys glareolus

Oksanen T., Oksanen L., Jędrzejewski W., Jędrzejewska B., Korpimäki E., Norrdahl K.

Polish Journal of Ecology

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2000

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Vol. 48, Suppl.

197-217

EN

Theoretical analyses and data suggest that the interaction between bank voles and their predators generates a locally stable equilibrium, regardless to the composition of the predator guild. The suggested primary proximate source for stability is female territoriality. Predation_per se_appears to be destabilizing. Whether or not predation regulates bank voles appears thus to be a semantic issue, depending on the operational definition of the concept of regulation. Confusion has arisen as different operational definitions have been tacitly used by different authors. The predicted intrinsic stability of bank vole-predator systems is most clearly displayed in the southern part of the boreal zone. Currently, even the dynamics of bank voles of taiga landscapes in Finnish ?apland are close to the predicted multiannual stability. In those boreal areas, where grassy and productive Microtus habitats are relatively abundant, sustained, multiannual cycles appear to be generated by the interaction between small mustelids and Microtus spp. When desities of Microtus decline, fidelity to Microtus habitats becomes suboptimal for predators. Consequently, cyclicity seems to be externally imposed on bank voles, due to changing habitat preferences of predators during the course of the mustelid-Microtus cycle. In the temperate zone, masting (seed crops of deciduous trees) increases the reproductive rate of bank voles and ameliorates female territoriality, initiating a transient increase in the numbers of bank voles and their predators. Beforethe system reaches its new equilibrium, the mast is over. Due to the combined effect of high predator numbers and normal reproductive performance, bank vole numbers then decline to the low level typicalfor post-mast years. Depending on the frequency of masting, the post-past low can be followed by a stable phase or immediately by a new mast-triggered outbreak. Although fundamentally different mechanisms appear to account for multiannual density fluctuations in temperate and boreal bank vole populations, both phenomena can be interpreted as consequences of extremal perturbations upon intrinsically stable predator-prey systems.

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Geographical differences in size, reproduction and behaviour of bank voles in relation to density variations

Yoccoz N., Hansson L., Ims R.

Polish Journal of Ecology

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2000

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Vol. 48, Suppl.

63-72

EN

The bank vole in Europe is hardly genetically differentiated, except in northern Fennoscandia, but shows large phenotypic variation. Body weight has been studied in the field and in the laboratory. Large bank voles are known in northern cyclic populations found on islands and in alpine areas. Reproductive patterns show that the length of the breeding season and the maturation processes may be more influenced by the fluctuation patterns than the length of the vegetative period. Behavioural differences are also known to occur between individuals from northern cyclic populations and individuals from southern stable populations. The relative importance of density fluctuations patterns and environmental harshness in causing geographical variation patterns is not known.