Avian communities in forested riparian wetlands of southern Michigan

There is a lack of information concerning the avifauna that inhabit midwestern riparian forests relative to riparian management and national wetland inventory objectives. For our study, we selected five undisturbed floodplain sites in the southern Lower Peninsula of Michigan. At each site, 0.64 ha circular sample plots were placed in a stratified random fashion in three forested wetland zones, and within forested upland areas adjacent to the floodplain (7--8 plots per site). Point-count surveys were conducted during the early, mid, and late breeding bird seasons (1998--1999) to assess the relative abundance and diversity of the breeding bird community in relation to the hydrology and woody plant structure and species composition measured within each plot (391 total point-counts). Trends in ground water depths were similar across forested wetland zones, which were consistently wetter than adjacent uplands. Plant species richness, dominance, and vegetation structure differed between forested wetlands and uplands, but were similar among forested wetland areas. Of the 115 bird species detected, 53 were categorized as breeders within our southern Michigan sites. Breeding bird abundance and richness were greater in the forested wetlands than within adjacent uplands, and 15 species had significantly higher breeding densities within forested wetland zones as compared to the upland. Thus, riparian zones in Michigan are important breeding habitats for an array of avian species not always found in upland sites.