Data from: Effectiveness of vole control by owls in apple orchards

1. Biological pest control is gaining greater acceptance as an important part of integrated pest management for sustainable agriculture. However, knowledge regarding biological control of rodent pests is limited, and its effectiveness in temperate areas has not been quantified. In traditional Japanese apple orchards, the Ural owl Strix uralensis breeds in tree hollows and preys on the Japanese field vole Microtus montebelli, a native pest species that can harm fruit production. In this study, we hypothesized that the Ural owl, a generalist predator, can act as a biological control agent by reducing vole densities in temperate orchards. 2. To quantify the pest control effects of breeding Ural owls, we first analysed the diet of individual owls nesting in apple tree hollows. Second, we installed nest boxes in orchards to attract breeding owl pairs and collected data on vole population changes around owl nests to compare with control areas. The population changes were analysed using a generalised linear mixed model to assess the effect of breeding owls within their breeding territory. The model took into account seasonal fluctuations in vole population size as well as surrounding land-use. We also examined vole populations around the owl nests in April, and the distance between nests and forested areas, to determine if these variables influenced nest site selection. 3. The primary prey of Ural owls breeding in orchards was voles, and the owls reduced vole populations within their estimated breeding territories by 63% (± SE: 53%–70%) compared with the predicted density without owls. Owls preferred to nest in orchards with higher vole population densities in April. Our findings also indicate that higher occupancy rates are possible by distributing nest boxes based on Ural owl breeding territory size (306 m radius circle in our study). 4. Synthesis and applications. As breeding Ural owls provided significant pest control effects within their breeding territories, the re-introduction of breeding Ural owl pairs within orchards will contribute to rodent pest control. Promoting the reproduction of native raptors in agricultural areas can be an option for developing integrated pest management while simultaneously maintaining regional biodiversity.04-Oct-2018Data of vole population countsdata.xls