The Eurasian eagle-owl (Bubo bubo) diet in the Trøndelag region (Central Norway)

Between 2008 and 2015 we collected pellets of the Eurasian eagle-owl (Bubo bubo) in the Trøndelag region of central Norway and identified the food remains in these samples. We collected material at 45 sites with samples from a total of 76 nests. Some of the samples were from older and already abandoned nests, but at several sites we also found and collected fresh B. bubo pellets. In total 40,766 items of prey were identified from the osteological material. The most dominant food components were mammals (Mammalia, 25 species, 63.5%). The species representation of birds was very diverse (Aves, more than 150 species, 19.4%). Of amphibians (Amphibia, 1 6.8%), the well-represented species were Rana temporaria. Fish (Pisces, 0.3%) were represented rarely, while invertebrates were represented only sporadically (Invertebrata, 0.05%). A special composition was found in the diet spectra of the mammals and birds in the mountainous areas at altitudes between 220-780 m above sea level. The highest proportion of frogs was found in areas in the proximity of the mainland shore. On the northern islands located near the coast a significant proportion of the B. bubo diet consisted of rodents (Rodentia). On the more isolated southern islands of Frøya, Hitra and Storfosna the main prey was sea birds, and of the mammals there were also hedgehogs and rats.