Diet of the Barn Owl (Tyto alba) and Little Owl (Athene noctua) in wetlands of northeastern Greece

The diets of the Barn Owl (Tyto alba) and Little Owl (Athene noctua) were studied through pellet analysis in four northeastern Greek wetlands. Results from the months February-September showed that in all areas, the most important prey for the Barn Owl were small mammals (mainly Mus spp., Microtus rossiaemeridionalis, Crocidura spp. and Apodemus spp.) The mammalian prey composition showed winter-summer and among-areas differences. Except in the Evros Delta, where small mammals were dominant by both numbers and biomass, the most numerous prey of the Little Owl were insects (mainly Orthoptera and Coleoptera), but small mammals (mainly M rossiaemeridionalis and Mus spp.) dominated the diet by biomass. Significant seasonal differences in prey composition occurred in the Evros Delta, while the summer diets were. also different among wetlands. Barn Owl median prey biomass (MPB) was significantly higher than Little Owl MPB in summer, whereas prey diversity and evenness values were higher in the latter species as a consequence of considerable amounts of insects in its diet. In both owl species, MPB differed significantly among the wetlands in the year of study, while seasonal differences occurred occasionally in some of the wetlands. The total prey overlap (Pianka's symmetric equation) of the two owl species in the summer (range 27\%-53\%) was lower than the mammalian prey overlap (60\%-97\%) and both were greater than those found by other authors in most parts of the Mediterranean.