The Significance of Hemlock for Breeding Birds in the Western Great Lakes Region

Several species of songbirds (Black-throated Green Warbler, Blackburnian Warbler, Solitary Vireo, Winter Wren, and Red-breasted Nuthatch_ show statistically significant associations with hemlock forests in Wisconsin and Upper Michigan. Comparisons of birds in managed forests with birds in the relatively pristine Sylvania Wilderness of Upper Michigan suggest that significant changes in bird species assemblages have resulted from the selective removal of hemlock from toady's landscapes. Stands which retain at the least some hemlocks and an uneven-ages forest structure support high bird densities compared with even-aged managed hardwood forests. Bird assemblages in isolated, hemlock, dominated natural areas of northern Wisconsin support unusually high bird densities and species richness. Bird assemblages in hemlock stands tend to show more local variability in bird density and, in the Nicolet National Forest, less numerical dominance by abundant species. Managed hemlocks are inhabited by characteristic hemlock bird species, but in many cases their densities are lower than in old growth sires. Many bird species characteristic of hardwood forests also occur in managed hemlock, however, giving managed hemlocks high species richness and high conservation value.