Lodgers, one after another

In the spruce trees before you, two birds use the same nest successively. Indeed, in the big spruces, the black woodpecker (Dryocopus martius) hollows out its nest, a box, directly in the trunk. After one breeding season, the woodpecker abandons its house. The Tengmalm´s owl follows it the year after, in order to lay its eggs and raise its offspring. So, if there are no old spruces, there are no black woodpeckers; no black woodpeckers and there are no Tengmalm´s owl!