There is a very good tounge-twister about woodpeckers:

"What would the woodpecker peck if the woodpecker wouldn't peck wood?"

This tounge-twister raises a very relevant question, does woodpeckers ever eat from anything else than wood? What are they eating in the wood?

Actually, woodpeckers of Europe does not eat the wood itself, but very often small animals, such as insects, that lives in or upon the wood. Woodpeckers are, therefore, very dependent upon trees to be able to find food. Some species of woodpeckers need large and old deciduous forests to survive, such as the middle spotted woodpecker (Dendrocopos medius) and the white-backed woodpecker (Dendrocopos leucotos). Old and large deciduous forests are today very scarce in Europe, this has resulted in large reductions of the species living in these areas. This is the case of the middle spotted woodpecker, for example, the middle spotted woodpecker went extinct from Sweden in 1983 due to reductions of its living areas. To decrease the reduction speed of the middle spotted woodpecker population it is important to know what they need in  its living areas. A lot of research has been done in this area and it is apparent that the middle spotted woodpecker requires large areas of very old trees, especially oak, but also beech, elm and others. But among these old trees, what are important for the woodpecker? Does it has to have a large circumference? A large crown? Short distances to neighbouring trees? I have tried to answer these questions during my masters thesis project.