Ábrahám Levente (szerk.): Válogatott tanulmányok IX. - Natura Somogyiensis 24. (Kaposvár, 2014)
Szűcs D. - Kitti Horváth K. - Horváth Gy. F.: Comparing small mammal faunas based on barn owl (Tyto alba) pellets collected in two different lowland landscapes
318 Natura Somogyiensis According to our results the first null hypothesis had to be rejected in the case of several small mammal taxa. The rank correlation of species frequency and the homogeneity test of the total species pool of the two investigated landscapes showed that the composition of small mammal fauna of the compared landscapes is basically the same, but the distribution of abundance was different between the landscapes on both the meso- and the microregional scale. Environmental factors such as climate, vegetation cover, food supply and the presence of competitors modifies the fundamental niche of species in characteristic ecological environment, so the realized niche is formed by the presence of competitors. Herrera & Hiraldo (1976) showed that the niche-range of owls separated in certain racial context, and they fulfill their energy demand form other components of food niche dimensions. The statistical analysis of niche parameters showed that bam owl niche breadths did not differ between the Drava plain and the Győr basin, because we studied only one owl species which is characterized by the same food composition due to its life-history strategy (prey preference and hunting strategy). However, niche overlap within each of the two mesoregions was higher than between the two, so we rejected the third null hypothesis. Askew et al. (2007) reported that bam owls select habitats within their home-range based on the abundance of field voles and possibly shrews, which demonstrates the density dependent predation of this owl species. In theoretical aspect the response of vertebrate predators includes two components: the numerical and functional response showed by predators when facing fluctuating mammalian prey populations (Jaksic et al. 1993, Hone & Sibly 2002, Hone et al. 2007). Besides, several studies have confirmed that the food composition of the bam owl as a typical farmland bird well-indicates the different land use which influences the distribution of prey through changing the composition and structure of landscapes (de la Pena 2003, Askew et al. 2006, Gonzáles Fischer 2012, Hindmarch et al. 2012). Thus, the examination of bam owl food composition on different spatial scales is very important for understanding predator-prey relationship on a landscape level and for drawing correct conclusions from the results of owl pellet analysis as an indirect method. Aknowledgements Pellet-based small mammal monitoring was supported by Duna-Drava National Park Directorate and Fertő-Hanság National Park Directorate. Scientific students’ associations and research of Dominika Szűcs was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 'National Excellence Program’. We want to thank László Bank, secretary of the Pécs Group of the Hungarian Ornithological Society for providing the pellet samples collected by the society. Moreover, thanks to all of the associates of Fertő-Hanság National Park who collected pellets in this region and to Gábor Takács ecological officer who co-ordinated these collections.
