, Volume 103, Issue 2, pp 241–248

Effects of predator removal on vertebrate prey populations: birds of prey and small mammals

  • Kai Norrdahl
  • Erkki Korpimäki
Original Paper

DOI: 10.1007/BF00329086

Cite this article as:
Norrdahl, K. & Korpimäki, E. Oecologia (1995) 103: 241. doi:10.1007/BF00329086


We studied the effects of removal of breeding nomadic avian predators (the kestrel, Falco tinnunculus and Tengmalm's owl, Aegolius funereus) on small mammals (voles of the genera Microtus and Clethrionomys and the common shrew, Sorex araneus) during 1989–1992 in western Finland to find out if these predators have a regulating or limiting impact on their prey populations. We removed potential breeding sites of raptors from five manipulation areas (c. 3 km2 each), whereas control areas had nest-boxes in addition to natural cavities and stick-nests. Densities of small mammals were monitored by snap-trapping in April, June, and August, and densities of mammalian predators (the least weasel, Mustela nivalis nivalis, the stoat, M. erminea and the red fox, Vulpes vulpes) by snow tracking in early spring and late autumn. The yearly mean number of raptor breeding territories was 0.2–1.0 in reduction areas and 3.0–8.2 in control areas. Breeding raptors alone did not regulate prey populations in the long term, but probably caused short-term changes in the population dynamics of both the main prey, the sibling vole (Microtus rossiaemeridionalis) and an alternative prey (the common shrew). The densities of an alternative prey, the bank vole (Clethrionomys glareolus) decreased in raptor reduction areas, most likely due to increased least weasel predation pressure in the absence of breeding avian predators.

Key words

Avian predator Least weasel Population fluctuation Population regulation Vole 

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • Kai Norrdahl
    • 1
  • Erkki Korpimäki
    • 2
  1. 1.Department of Zoology, Division of EcologyUniversity of HelsinkiFinland
  2. 2.Laboratory of Ecological Zoology, Department of BiologyUniversity of TurkuTurkuFinland

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