Avian predation has the strongest impact on vole survival during winter and spring in temperate grasslands

Predation is a key driver of small rodent population dynamics, yet experimental evidence on the role of avian predators in temperate ecosystems remains limited. We conducted a year-round, spatially replicated field experiment in temperate grassland habitats to test how exclusion of birds of prey affects the survival and abundance of root voles (Microtus oeconomus). In each of the three pairs of plots, predators were excluded from one plot by overhead netting. Vole survival and population size were assessed using capture-mark-recapture method, considering the effects of sex and body mass. Avian predation reduced vole survival by up to 22%, with the strongest effect in winter and spring. Predator exclusion led to short-term increase in vole numbers during spring, but did not produce sustained differences in abundance. The effect of avian predation was not selective regarding sex, but heavier voles showed reduced overwinter survival. Effect of predation varied among sites, with the strongest impact observed at the location nearest to a forest edge. Our results demonstrate that avian predators can substantially contribute to vole mortality in temperate open habitats, even under snow cover, and highlight how seasonal predation may be altered by climate-driven changes in snow conditions and vegetation phenology.