Effects of American Kestrel Nest Boxes on Small Mammal Prey in Cherry Orchards

Abstract

In order to potentially reduce use of environmentally damaging rodenticides, integrated Pest Management (IPM) for rodents, or Ecologically Based Rodent Management (EBRM), proposes a more sustainable management approach using strategies informed by an increased understanding of rodent population and community ecology, including interactions with important predators, such as raptors. Nest boxes and perches can encourage raptor presence in agricultural areas and potentially enhance the regulatory ecosystem services provided by raptor predation of agricultural pests. To assess this idea, we studied American kestrels (widespread, generalist predators that readily use nest boxes) in a fruit-growing region of northwestern Michigan. The most common mammal prey in the diets of these kestrels from 2013 through 2016 were voles, which are considered the most important rodent pests in temperate fruit orchards. We utilized live trapping to measure small mammal abundances and activity during the summer at sites with and without active kestrel nest boxes; furthermore, we utilized camera trapping to measure small mammal presence during the winter, when damage to trees is most likely. As predicted, small mammal abundance and activity was lower at orchards with active kestrel boxes and at orchards that had been more recently mowed; however, these differences did not carry over as differences in winter presence in orchards. Our sampling demonstrated that voles were absent from orchards during both summer and winter, which suggests that orchards offer insufficient cover except under certain conditions, such as sustained snow cover. Instead, mice were the most abundant small mammals in most orchards during the summer and were also present during the winter. More evidence is therefore needed to determine the extent of orchard damage attributable to Peromyscus spp. and whether indirect effects of kestrels on Peromyscus spp. may reduce damage. We provide recommendations for future research on the effects of raptor predation in orchards.