Spatial and temporal changes in the diet composition of the Eurasian eagle-owl ( Bubo bubo) in Slovakia comparing three historical periods

• Published in: Raptor Journal
• Main Author: Obuch, Ján
• Format: Article in Journal/Newspaper
• Language: English
• Published: Walter de Gruyter GmbH 2021
• Subjects: Common vole; eurasian eagle-owl; Microtus arvalis
• Online Access: http://dx.doi.org/10.2478/srj-2021-0002; https://www.sciendo.com/pdf/10.2478/srj-2021-0002

Abstract The author evaluates his own data on the food of the Eurasian eagle-owl ( Bubo bubo ) in Slovakia using material he collected between 1975 and 2020. A total of 105,543 food items were identified in 254 samples taken at 136 localities. Mammals had the highest representation (Mammalia, 65 species, 58.4%), and the species composition of birds was diverse (Aves, minimally 140 species, 8.5%), but the common frog ( Rana temporaria , 32.0%), from the lower vertebrates, is represented more abundantly. Invertebrates (Evertebrata, 0.1%) occurred in food residues only occasionally. The bulk of the samples were collected from eagle-owl nests. The samples were divided into three time periods (A–C), which differ in the manner of human land-use management: A up to the 1950s, with a smaller area of field plots and more extensive grazing in the uplands; B from the 1950s to the 1980s, during the Socialist period, with the concentration of agricultural production in large units; C the last 30 years, 1990 to 2020, with the gradual break-up of collective land management. The first period (A) is characterised by a strong dominance of frogs, particularly the European brown frog R. temporaria (44.6%), and a large share of small mammal species of the family Muridae (genera Apodemus and Mus ). During the time of Socialism (B), eagle-owls adapted to hunting larger species of mammals and birds, and the share of frogs in their food fell by half ( R. temporaria , 23.3%). With the decline in livestock production after 1990 (period C), the species diversity of birds increased: aquatic species and raptors in particular are on the rise. Successive overgrowth of pastures in the submontane zone is reducing the hunting territories of eagle-owls. The dominance of the common vole ( Microtus arvalis ) in their diet has gradually increased from period A (26.8%) to period C (37.3%). Data from eleven areas around Slovakia are evaluated separately for the three time periods. In period A, the highest proportion of frogs was in the Liptov region ( ...