A multitude of wild animals live in the beech forests of the Harz Mountains. Over 5,000 species, most of them insects, have their home in these woods. They include many species that help to decompose leaves and work them into the soil and ground cover, including springtails, oribatid mites, woodlice, roundworms, millipedes, earthworms and snails. Characteristic breeding birds in the beech woods, with their abundance of dead wood, are the black woodpecker (Dryocopus martius) and stock dove (Columba oenas). An indication of the natural state of the beech woods in the Harz is the return of the black stork (Ciconia nigra). This shy and susceptible resident of richly diverse deciduous and mixed forest has become very rare in central Europe due to increasing disturbance of its habitat (caused by a lack of old trees and natural brooks). Through improvements to its habitat, including the renaturalisation of waterways and the creation of relatively undisturbed peaceful areas, the black stork population has now recovered. A typical mammal of such deciduous woods is the European wildcat (Felis silvestris), that has established a stable population in the Harz. It prefers the diverse wooded areas, which offer a rich variety of food.