Characteristics of trees preferred by foraging middle spotted woodpecker Dendrocopos medius in northern Switzerland

The endangered Middle Spotted Woodpecker Dendrocopos medius is restricted to oak forests. We analysed this woodpecker's foraging trees and behaviour in a coppice-with-standards wood in the Swiss lowlands. Oaks Quercus spp. were highly preferred and their diameter at breast height mainly ranged from 36-72 cm, corresponding to an age of > 120 years. Over 78% of the foraging observations were made in oak crowns, and among these, medium-sized were used most frequently. Regarding their contacts with adjacent ones, the birds preferred crowns with none or one contact, whereas those with ≤ 3 contacts were avoided. Dead trees were used randomly for foraging and, within a tree, only 122 out of 436 foraging observations were made on dead substrate. Searching and probing were the most frequently observed foraging techniques. For the support of this species, a long-term management of moderately harvested forests containing old oaks is needed.