Book Description

Wetlands are one of the fastest disappearing habitats in America. Many wetlands are also being altered due to the effects of various types of land use. Because wetlands provide important habitat for many types of birds, these species can be affected by changes in wetlands due to land use. The impacts of several wetland features, including wetland size, proximity to other wetlands, and vegetation, on bird communities have been debated in the literature. While some studies have found landscape-level features, such as connectivity to other sites to be the most important factors for explaining bird diversity, others have found within-patch characteristics to be more important. It is also unclear how these variables affect rates of nest predation in wetlands. The purpose of this study was to analyze the effects of several wetland features on wetland bird assemblages and nest predation rates at several spatial scales. Bird surveys, vegetation surveys, and measurements of nest predation were conducted at the Cedar Creek Natural History Area in East Bethel, Minnesota. Landscape analyses were conducted at four different spatial scales. Results showed that wetlands are used extensively, not only by species that breed in wetlands, but by species that breed in other environments as well, particularly by woodland birds. Results also indicated that diversity in vegetation structure is associated with an increase in the number of species using wetlands. Low bird species richness in wetlands was associated with increased amounts of agriculture and urban development, which was due to the reduction in trees in agricultural and developed areas. Unlike studies of upland species, birds responded the same way to urban development as to agriculture in the landscape. Features at both the habitat level and at broader landscape scales were found to be significantly correlated with features of the bird communities, indicating the importance of implementing conservation plans at multiple spatial scales. Results suggest that for restoration and construction of wetlands, increasing the variation in both vertical and horizontal structure within the wetland and in the surrounding landscape will increase the bird diversity within the wetland. The results of this study suggest that further encroachment of development and agriculture on wetlands in East Central Minnesota will lead to a decline in wetland bird diversity, particularly with respect to woodland birds that use the wetlands for foraging purposes. The data suggest that woodland obligates will disappear first from the area, followed by sensitive wetland obligates.