EFFECTS OF EDGE TYPE AND PATCH SHAPE ON AVIAN COMMUNITIES IN A MIXED CONIFER-HARDWOOD FOREST

Forest bird communities were sampled along line transects in northwest ern Wisconsin during June of 1985 through 1992 to determine whether ed ge type and patch shape affect avian abundance, Landscape structural c haracteristics quantified along these transects included: (1) edges th at defined the habitat patches they separated, (2) fractals to quantif y patch shapes, and (3) areal extent of different patches. Three multi ple-regression models were constructed for 10 bird species and the mea n number of individuals and species using the following sets of indepe ndent variables: (1) edge variables and fractals, (2) area variables, and (3) the first six components from a principal components analysis based on all independent variables. Multiple-regression analysis indic ated that edge variables and fractal dimension explained the most vari ation in abundance for Black-capped Chickadees (Parus atricapillus), R ed-breasted Nuthatches (Sitta canadensis), Hermit Thrushes (Catharus g uttatus), and American Robins (Turdus migratorius). In contrast, area variables explained the most variation in abundance for Red-eyed Vireo s (Vireo olivaceus), Chestnut-sided Warblers (Dendroica pensylvanica), and Ovenbirds (Seiurus aurocapillus). Abundances of Yellow-bellied Fl ycatchers (Empidonax flaviventris), Common Yellowthroats (Geothlypis t richas), and White-throated Sparrows (Zonotrichia albicollis) were equ ally correlated with both edge and area variables. Results of our stud y show that, for selected species, forest management strategies must b e developed that consider not only stand characteristics, but also the edges created between these stands.