Changes in the tawny owl Strix aluco diet along an urbanisation gradient

Abstract

The aim of this study was to describe how the diet of tawny owl changed along an urbanisation gradient. The research was conducted from 2003 to 2011 in central Poland. Pellets were collected in the following zones: the center of Warsaw, capital city of Poland (inhabited by approximately 2 million people), its outskirts and rural areas beyond the city. To investigate the differences in the percentages of the main groups of prey between the three zones, a redundancy analysis (RDA) method was implemented using CANOCO software. Sparrows, rats, pine voles and striped field mice were most connected to the city center, whereas voles (all species pooled together), northern birch mice, hazel dormice and insects were more commonly found among prey items collected in rural areas. As the outskirts were transitional areas where different habitats typical for both rural areas (such as forest complexes) and urban areas (such as parks or built-up areas) were present, no prey group was strongly connected to this landscape. Mammals were dominant in the diet in winter in all habitat types. Their share ranged from 52% (in the city center) to approximately 90% in the outskirts and rural areas. Birds, amphibians, reptiles and insects were more frequent in summer. Overall, the study confirmed high plasticity of the species as an opportunistic predator and its ability to adapt to long-term changes in its main prey in most urbanized areas.