PARENT SESSION
Poster Session # 18: Avian Ecology.
Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Forest bird monitoring in northern Minnesota and Wisconsin 1991-2002.
Danz, Nicholas*,1, Lind, Jim1, Hanowski, JoAnn1, Niemi, Gerald1, Jones, Malcolm1, 1 Natural Resources Research Institute, Duluth, MN, USA
ABSTRACT- The western Great Lakes region has among the highest richness of forest breeding bird species in the continental US and is often considered a bird population source for agricultural landscapes in the lower Midwest. A long-term regional monitoring program was implemented in 1991 to address concerns over potential declines of forest breeding species in the region. About 1400 permanent sampling points were located in four study areas so that the sample was representative of the forest within each area. Birds were surveyed annually by experienced observers using 10-minute point counts. To characterize population trends, which are directional changes in population size over a specified time period, we used simple linear regression to model an index of abundance as a function of time. Trends were computed for species having a minimum level of occurrence; the number of species tested per study area ranged from 40 to 53. The ratio of increasing:stable:decreasing species was consistent at about 1:3:1 across the four study areas, although the identity of species in each trend direction category changed somewhat across the areas. Six species showed consistent increases across the areas: Least Flycatcher, Red-eyed Vireo, Black-capped Chickadee, Cedar Waxwing, Chestnut-sided Warbler, and American Redtart. Nine species showed consistent declines: Eastern Wood-Pewee, Winter Wren, Hermit Thrush, Ovenbird, Connecticut Warbler, Mourning Warbler, Common Yellowthroat, Song Sparrow, and Brown-headed Cowbird. With the exception of nesting strategy, there were no common threads to explain the pattern of increasing and decreasing species. No species that nest on the ground had increasing trends, while seven of the eight declining species that build nests do so on the ground. We are investigating the hypothesis that decreased abundance of ground nesting birds is related to a recent regional increase in forest edge and a concomitant increase in mammalian nest predators surrounding edges.
Key words: Great Lakes , monitoring, forest birds