Long-Term Temporal Change of Small Mammal Composition and Abundance in the Food Intake of the Western Barn Owl (Tyto alba), Comparing Two Different Lowland Mesoregions.

The change in the composition and diversity of small mammal assemblages, as well as the diet composition of the Western Barn Owl, has long been researched around the world; however, there are few long-term studies in Hungary. The object of this study is to evaluate and compare the changes of the small mammal assemblages between two lowland areas. We analyzed Western Barn Owl pellets collected between 2000 and 2023 to investigate the long-term temporal change of small mammal composition and abundance in the owls' diet. We investigated the regional differences in small mammal community structure by iNEXT, PERMANOVA, and RAC analysis. Generalized additive models (GAMs) and generalized additive mixed models (GAMMs) were applied to analyze the temporal change of diversity and community dynamic characteristics (turnover, rank change, and rank shift) of small mammal assemblages and the time- and area-dependent abundance change of the consumed prey taxa, as well as the impact of weather conditions. The abundance of prey species was significantly different between the two areas. Based on our results, the diversity indices of the Western Barn Owls' diet were significantly higher in the Győr basin than in the Drava floodplain. Our GAM and GAMM results confirmed that there were significant temporal and spatial changes in the diversity indices, the rank shift, and the abundance of prey taxa. These findings suggest that prey occurrence and small mammal community structure can vary depending on local environmental factors, and the examination of Western Barn Owls' food composition can contribute to understanding the change of these assemblages under changing conditions.