Rapid Tracking of Microtine Populations by Their Avian Predators: Possible Evidence for Stabilizing Predation

Abstract

I show that there are no time lags between population fluctuations of Tengmalm's owl, short-eared owl, longeared owl, kestrel and hen harrier and their microtine prey in western Finland. This is because of the high degree of mobility of these vole specialists, but also during rodent scarcity there was a small population of these birds of prey breeding in the study areas. These species also responsed functionally to the microtine cycles. Since time lags tend to make predator-prey systems unstable, the observed rapid tracking of vole populations by their predators seems to indicate that nomadic vole specialists may possibly stabilize small mammal populations by truncating population peaks. Also the predation pressure by breeding Tengmalm's owls on small mammals in the different phases of the cycle accorded with this prediction. Moreover, because of their resident habits and diet, eagle, tawny, ural and pygmy owls may also have a similar role in microtine cycles in Fennoscandian taiga, especially in areas with thin snow cover.