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
306 Natura Somogyiensis Owl pellet analysis is a useful indirect method for gaining additional insight into small mammal communities and distributions (Bonvicino & Bezerra 2003, Torre et al. 2004, Santos-Moreno & Alfaro Esoinosa 2009). Although, there is no consensus among researchers that owls sample their prey randomly, partly due to the absence of knowledge about the real abundance of their prey (de la Pena et al. 2003). Despite of the selective predation (von Knorre 1973, Derting & Cranford 1989, Askew 2007) and thus the potential bias of indirect sampling, the last decade’s studies showed that investigation of bam owl’s food composition is the most suitable method in the landscape- level analysis of small mammal data (de la Pena et al. 2003; Askew et al. 2006, 2007). The studies based on the effects of changing agricultural landscape mosaic on the composition of the small mammal assemblages showed that the intensification of agriculture has negative effects on the density of rare and habitat-specialist species, while it favours habitat-generalist species, some of them being known to exhibit fluctuating density (de la Pena et al. 2003). Love et al. (2000) also demonstrated dietary changes of bam owl which emerged due to more intensive agriculture. Bond et al. (2004) investigated the effect of landscape parameters on the breeding success of bam owls. Their results showed that land cover was less heterogeneous at successful sites and unsuccessful nesting sites had significantly more improved grassland, suburban land and wetlands than successful sites. Owl pellet analysis, being an indirect method is acceptable from a conservation aspect and is a relatively fast way of collecting large amounts of occurrence data. The collection and investigation of the bam owl’s pellets is the most appropriate method for studying small mammal fauna (status survey, monitoring, estimation of species richness), because among the owl species occurring in Hungary this is the one with the widest selection of prey, and also its feeding ecology is well studied (Kalivoda 1999). Bam owl pellet analysis in Baranya county has been carried out since 1985 (Horváth 1994-, 1995, 1998, 1999; Horváth & Majer 1995). At Győr-Moson-Sopron county extensive small mammal faunistic studies were performed by collecting and analysing pellets from several owl species (Andrési & Sódor 1981a,b, Jánoska 1992, 1993). Within both landscapes the subprogramme based on national owl pellet studies was started under the Hungarian Biodiversity Monitoring System (HBMS) program in 2000 and extended to cover the faunistic surveys of small mammals. As the result of that subproject, the data of owl pellet landscape-level analysis related to the monitoring of the upper section of Drava River was achieved on larger spatial scale. Differences between the compositions of the small mammal communities were evaluated depending on the landscape pattern of each section of the Drava (Horváth et al. 2005). Although the synthesis of the results in this project has been not been achieved yet, data were suitable for comparing small mammal faunas of landscapes which were studied intensively on regional scale (eg. Horváth et al. 2008). The aim of this study is to compare the composition of small mammal assemblages of two lowland mesoregion landscapes (Drava floodplain and Győr basin), and evaluate the abundance of species on three different spatial scales (meso-, microregions and local scale). We investigated three null hypotheses: the distribution of species frequency values is homogeneous between two landscape areas (H01), there are no significant differences in the frequency orders in meso- and microregional scale (H02), and niche parameters do not show differences between the two lowland landscapes based on the characteristic dietary preference of the bam owl (H03).
