Apodemus mice as the main prey that determines reproductive output of tawny owl (Strix aluco) in Central Europe

During the years 2008-2014, we studied diet composition, the number of breeding pairs, and reproductive output of tawny owls in Central Europe (Czech Republic) in relation to availability of main prey in the field. We also performed a meta-analysis on diet composition of tawny owl in Europe that confirmed the important role of Apodemus mice in tawny owl diet in Central Europe. In concordance, Apodemus mice were the main prey of tawny owl in our study area (38.7%), and Microtus/Myodes voles (15.4%), birds (12.1%) and others (33.8%) were alternative prey. We found a positive relationship between the proportion of Apodemus mice in the diet and their abundance in the field (beta = 0.23, P = 0.001). Availability of main prey (Apodemus mice, Microtus/Myodes voles or Sorex shrews) in the field was not correlated with the number of breeding pairs. Proportion of birds in diet (expressed by scores from multivariate analysis), which was inversely related to proportion of Apodemus mice, was positively correlated with laying date (beta = 0.66, P = 0.012) and negatively correlated with clutch size (beta = - 0.45, P = 0.004) and brood size (beta = - 0.16, P = 0.076). We also found negative relationships between laying date and clutch size (beta = - 0.13, P = 0.014) and brood size (beta = - 0.07, P = 0.057). Our results support the idea that diet and breeding ecology of owls in Central Europe is mainly driven by the availability of Apodemus mice that are suitable prey due to their similar habitat requirements and nocturnal activity.