treecreeper (Certhia familiaris), coal tit (Parus ater) and crossbill (Loxia curvirostra). Special mention should be made here of the pygmy owl (Glaucidium passerinum) which is threatened with extinction and which lives in the submontane to subalpine zones within mixed and pine forests interspersed with open areas. They prefer spruce woods for breeding, but feed in more open stands of trees or on open moorland. Like the black stork, the pygmy owl had long since disappeared from the Harz, but returned in the 1980s of its own volition, as its ancestral homeland once again became more natural, so that there was sufficient food to support it (insects, small mammals and small birds) as well as standing dead wood (spruce trees with woodpecker holes).