Density of suitable wood duck nest cavities in a northern hardwood forest

The density of natural cavities suitable for wood duck (Aix sponsa) nesting, and the relative importance of cavity and potential cavity tree species were determined in a second growth hardwood forest in central Wisconsin. Suitable cavity density averaged 0.65/ha, with silver maple (Acer saccharinum), sugar maple (A. saccharum), quaking aspen (Populus tremuloides), and American basswood (Tilia americana) containing suitable cavities. These 4 species, which typically occur in Wisconsin\u27s wet-mesic and mesic woodlands, were of highest importance in the forest\u27s composition of large (≥31 cm diameter breast ht [dbh]) trees. Although the density of suitable wood duck nest cavities was not high, cavities are nevertheless abundant because large areas of forest are available for wood duck nesting. Numbers of cavities should increase as Wisconsin\u27s second growth forests continue to mature. Wildlife managers will have a greater impact on wood ducks by advising on forestry operations, rather than actively providing nest sites