The Legacy of Shade: Use of abandoned pasture trees by birds and mammals in second old growth forests of Vermont

Gaige, Michael
Department of Environmental Studies
2009
Complex structure is important to forest wildlife all over the world including forests of the Northeast. Structural complexity in forest ecosystems generally increases in quality as a forest ages. The northeast generally lacks old forests but it does contain old trees. Scattered throughout the second-growth forests are large, old, wide-spreading trees that formerly stood in open pastures. Commonly called wolf-trees, these cultural legacy trees are characterized by their large size, horizontal structure, hollows, cavities, and rugose bark. The use of these structural anachronisms by wildlife is not well understood and forest management often suggests removing such trees in favor of cultivating valuable timber. Others suggest that the trees may have wildlife or aesthetic value. I investigated use of abandoned-pasture-trees by birds and non-volant mammals in second-growth forests of Vermont. I selected 28 legacy trees and 28 paired control trees and sampled for wildlife using four methods: time constrained observations; time constrained searches for sign; small mammal trapping; and motion sensing cameras. The number of observations or detections for birds and mammals were higher at legacy trees (n=368) than matrix trees (n=153). Use duration by birds at legacy trees (11,140 sec.) was greater than use duration at control trees (1170 sec.). Feeding, singing, and nesting behavior by birds was more common at legacy trees. Small mammal use was not significantly different. The number of species using legacy trees was higher (n=46) than control trees (n=27). The results of this study highlight the attractiveness of abandoned-pasture-trees for wildlife in the northeast and call for appreciation of individual malformed trees as important wildlife features. While managed forests inherently remain in a relatively young successional stage, the retention and encouragement of legacy trees can add important old-growth type features to an otherwise structurally simple forest.