The object of this study was to assess the impact of avian predators on Microtus townsendii populations, especially during declines. Four vole populations declined from October 1977 until June 1978, and in the fall of 1977, avian predators accounted for a minimum of 15% of the loss from the tagged vole populations, but this percentage declined during the winter of 1977. The predators selected males and small individuals and mortality accounted for by avian predation was density dependent in the vole populations; denser vole populations suffered higher predation rates.