Experts point out that the owls would only go for smaller targets out of necessity: the relative scarcity of common shrew and field vole remains in the pellets shows that the two species must have gone downhill.
The decline of voles is attributed largely to the diminution of rough grassland, in which they thrive. The British population is still thought to be about 75 million, but the Mammal Society believes that the number is too small, and that any further fall will have serious effects on the survival of the predators - kestrels and weasels beside barn owls - which live on them. The society is therefore launching new research to develop techniques for monitoring further population changes.
Voles might have better survival rates if they could learn to make less noise. As it is, the squeaking and chittering of territorial disputes betray their presence to owls, which hunt with ears as well as eyes.Reuse content