Influence of surrounding vegetation on woodpecker nest tree selection in oak forests of the Upper Midwest, USA

This study examined the influence of forest context on woodpecker nest tree selection, which has implications for forest managers leaving trees during timber harvest for cavity nesting birds. We surveyed habitat variables in 11.3 m radius subplots centered on 165 active woodpecker nest trees and 144 randomly selected points in oak forests of southeastern Minnesota and western Wisconsin in 1997-1998. Forward stepwise sequential F-tests indicated that the number of potential nest trees and basal area (BA) of dead elms were the most important variables in distinguishing nest sites and random sites. Discriminant function analysis correctly classified 71% of the observations. However, a comparison of nest sites only to those random sites containing a tree likely suitable for nesting showed no differences. This suggests that nest tree has a greater influence in nest site selection than does surrounding vegetation. Yellow-bellied sapsucker nest trees were surrounded by a significantly higher BA of trembling aspen (Populus tremuloides) and density of mast-producing trees than the nest trees of the downy, hairy, red-bellied, red-headed, and pileated woodpeckers, and the northern flicker. However, we found no interspecific differences among downy, hairy, red-bellied, and red-headed woodpeckers. This study is significant because it indicates forest management for cavity nesting birds should focus on providing suitable nest trees within the larger forest context; vegetation immediately surrounding nest trees may have minimal influence on woodpecker nest tree selection.