LOCAL CHANGES IN A BREEDING BIRD COMMUNITY FOLLOWING FOREST DISTURBANCE

Species composition and population sizes of breeding birds changed sub stantially in less than 10 yr following local disturbances in a mixed deciduous forest plot in Itasca State Park, northern Minnesota. Dutch elm disease, drought, and windstorms changed a closed-canopy elm-birch -ash forest to a more open habitat dominated by basswood, ash, and sta nding snags with large areas of dense fern cover. Breeding bird census es conducted in 1979-1981 and 1990-1992 showed substantial changes in local populations of several species including Ovenbirds (Seiurus auro capillus) (20.0 territories/10 ha in 1979-1981 to 1.6 in 1990-1992), V eeries (Catharus fuscescens) (4.1 to 0.9), Mourning Warblers (Opororni s philadelphia) (0.7 to 5.5), Song Sparrows (Melospiza melodia) (0.0 t o 6.4), and White-throated Sparrows (Zonotrichia albicollis) (0.0 to 7 .1). These changes were related to increased density of ground vegetat ion and increased light levels. Spatial distribution of species showin g major increases was strongly associated with the locations of patche s of dense undergrowth. Arboreal species showed less population change between census periods than did ground foragers. These local populati on changes were unrelated to trends over the same period on a 15-km ro adside survey in the park. Changes in species abundance on the plot ap pear to be caused by local habitat change rather than broader-scale pr ocesses.