Barn Owl habitat: Vole holes and other signs of Field Voles Barn Owls need a plentiful supply of prey mammals – their favourite, in the UK, is the Field Vole. Here’s a photo guide all about Vole holes and how to spot them. If Field Voles are present, their holes may be spotted easily from November to March Nationally, Field Voles comprise 45% of Barn Owl diet. In really good rough grassland, vole holes can average 2 per square metre. Most Field Vole tunnels (or ‘runs’) do not go underground but simply through the ‘litter-layer’. Field Voles emerge to graze on the surface . . . . . . but spend most of their time in a complex matrix of ‘vole runs’ that lead to their nests and latrines. Nests consist of finely-chewed grasses in a slight depression in the ground or at the base of a tussock. Most latrines are hidden in a ‘run’ but this one was ‘open-air’ in the base of a rotted thistle. The key requirement of good habitat is the ‘litter-layer’ as shown in this cross-section view. Unfortunately, the combination of vole-rich verges and unscreened traffic is often fatal for Barn Owls. Click on a photo to scroll through the gallery. Click on the black background or press esc to return to this page. Good Barn Owl habitat. How to manage land for Barn Owls.