Voles have been a constant at the farm. They come and go under the cover of darkness, living in the fields, barns, root balls of shrubs, and possibly in various car ventilation systems. To curb the proliferation of these little vermin the pervious owner of the home built a number of traps that he baited with fish pellet poison. After last years vole destruction I have devoted a prized piece of NEW 5/8" plywood to the project of building a few more bait boxes (shown below). The plus of building these boxes is that you can poison the voles and field mice but not dogs, cats, and deer. I am not sure about birds but I have not seen any birds enter the boxes. Although a simple project, come summer the grass will look much better and hopefully some of the shrubs, bushes, fruit trees, and grape vines will not have been pillaged by the voles.
The greatest virtue of man is perhaps curiosity ~Anatole France~