Diet shifts of the tawny owl Strix aluco in central and northern Italy

Abstract

Feeding of tawny owl, Strix aluco, was studied from 14 localities of northern and central Italy, where it preyed mainly upon mammals and birds, but amphibians and invertebrates were also frequently eaten. Predation upon mammals was more important from autumn to spring, when alternative prey (amphibians, birds and invertebrates) were less available. The food niche overlaps, the linear distances (in km) between the various localities were negatively correlated, and the mean size of prey taken increased with the proportion of forested territory. However, where tawny owl preyed upon large forest mammals, it also preyed upon larger mammals not typical of forests. Considering the relationships between forest structure and tawny owl diet, it was found that forest density was positively correlated with the proportion of arvicolids and negatively with prey size diversity and the proportion of myoxids. The amount of forest territory within 1 km radius from each pellet collection site largely explained diet variability. Results of discriminant analysis, in addition, suggested that tawny owl is likely to avoid thick Mediterranean coppice forests as hunting habitats.