RESIDUAL PATCHES AND THEIR CONTRIBUTION TO FOREST-BIRD DIVERSITY ON NORTHERN MINNESOTA ASPEN CLEARCUTS

Managers of upland forest generally operate with the assumption that l eaving residual timber in clearcuts is beneficial for wildlife. Our pr imary objective in this study was to evaluate the contribution of resi dual patches to forest birds by (1) characterizing differences in comp onents of bird diversity between clearcuts with and without residual p atches, (2) characterizing differences in components of bird diversity between residual patches and clearcut edges, and (3) describing any c learcut-wide effects of residual patches for any bird species or group . Breeding birds were surveyed in 40 aspen clearcuts (20 clearcuts wit h and 20 clearcuts without residual patches) 3-9 years old from May to July 1993 in northern Minnesota. Sixteen additional survey points wer e established, eight each in clearcut edge and in clearcuts with resid ual patches but with the survey point outside the residual patch. Two diversity indices, four avian nesting guilds, and 12 bird species show ed significant differences between treatments when analyzed with multi ple regression analysis and analysis of variance. Five of the seven sp ecies significantly associated with residual patches are of high regio nal management concern: Veery (Catharus fuscescens), Ovenbird (Seirus aurocapillus), Rose-breasted Grosbeak (Phucticus ludovicianus), Canada Warbler (Wilsonia canadensis), and Black-throated Green Warbler (Dend roica virens). Results from this study suggest that residual patches c ontribute to forest-bird diversity in northern Minnesota aspen clearcu ts, and may enhance bird populations on regional and landscape scales.