Comparing small mammal faunas based on barn owl (Tyto alba) pellets collected in two different lowland landscapes

Abstract

The composition of small mammal assemblages was analysed in two lowland landscapes (Drava floodplain, Győr basin) and was evaluated on three different spatial scales (meso-, microregions and local scale), based on barn owl pellets collected between 2006 and 2009. Altogether 273 pellet samples were collected from 41 settlements of the two regions during the four years of monitoring. The analysed 6978 pellets contained 17214 small mammal individuals. The distribution of the relative abundance of small mammal taxa was evaluated as well as the correlation of frequency order on a meso- and microregional scale in the comparison of the two lowland areas. The food niche parameters of barn owl were calculated on a local scale, regarding the breeding pairs. 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 rank of frequencies (H02) in meso- and microregional scale; and niche parameters of the barn owl do not show difference between two landscapes (H03). The first null hypothesis had to be rejected in several cases of small mammal taxa. The rank correlation of species frequency and the homogeneity test of total species pool of 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 landscapes on both meso- and microregional scales. The statistical analysis of the niche parameters showed that the barn owl’s niche breadth did not differ between the Drava floodplain and the Győr basin. However, the niche overlap within each of the two mesoregions was higher than between them, and thus we rejected the third null hypothesis. This provides a further evidence that besides the species-specific hunting strategy, the regional differences of the quantitative relations of small mammals is also reflected in the dietary composition of the barn owl.