Residual patches and their contribution to forest-bird diversity on northern Minnesota aspen clearcuts

Managers of upland forest generally operate with the assumption that leaving residual timber in clearcuts is beneficial for wildlife. Our primary objective in this study was to evaluate the contribution of residual patches to forest birds by (1) characterizing differences in components of bird diversity between clearcuts with and without residual patches, (2) characterizing differences in components of bird diversity between residual patches and clearcut edges, and (3) describing any clearcut-wide effects of residual patches for any bird species or group. Breeding birds were surveyed in 40 aspen clearcuts (20 clearcuts with and 20 clearcuts without residual patches) 3-9 years old from May to July 1993 in northern Minnesota. Sixteen additional survey points were established, eight each in clearcut edge and in clearcuts with residual patches but with the survey point outside the residual patch. Two diversity indices, four avian nesting guilds, and 12 bird species showed significant differences between treatments when analyzed with multiple regression analysis and analysis of variance. Five of the seven species significantly associated with residual patches are of high regional management concern: Veery (Catharus fuscescens), Ovenbird (Seirus aurocapillus), Rose-breasted Grosbeak (Phucticus ludovicianus), Canada Warbler (Wilsonia canadensis), and Black-throated Green Warbler (Dendroica virens). Results from this study suggest that residual patches contribute to forest-bird diversity in northern Minnesota aspen clearcuts, and may enhance bird populations on regional and landscape scales.