Schweiger, A; Lipp, L: Voles (Arvicolinae) as preferred prey of Bavarian Eagle Owls Bubo bubo (L.) during the nestling period, Ornithologischer Anzeiger, 50(1), 1-25 (2011)
A sufficient choice of prey with adequate size is quoted in numerous surveys about feeding ecology of the Eurasian Eagle Owl as one of the most important factors allowing the survival of a successful population. On the other hand a high proportion of small animals in the diet is regarded as an indicator of malnutrition, and a threat to the successful maintenance of the greatest European Owl. Examination of prey items, mainly from the breeding season, over 33 years (1976-2008), in three Bavarian subpopulations of the Eagle Owl reveals a very different and conflicting pattern. Uni- and multivariate statistical evaluation were based on a quantification of food diversity, favoured size of prey and percentage proportion of particular prey items in the diet of fledging Eagle Owls. The results from this survey show a clear preference of Bavarian Eagle Owls for voles (Arvicolinae). The diversity of prey actually declines with increasing proportion of voles. An increasing amount of major prey like waterfowl leads to a greater prey diversity. Even so, comparison between Bavarian sub-populations of Eagle Owl shows both considerable regional differences and clear temporal differences and changes in prey spectrum, caused e.g. by changes in landuse. In general Bavarian Eagle Owls take small mammals in large quantities while rearing their young. Larger prey items are presumed to increase in importance when voles are scarce or when food requirements increase towards fledging.

last modified 2013-03-12