Invasive plants are a primary contributor to loss of biodiversity worldwide. In southern Minnesota, many wetlands have been invaded by reed canarygrass (Phalaris arundinacea). The current perception among ecologists and resource managers is that these wetlands are of little value to wildlife, yet little is known about the effects on birds of the widespread conversion of diverse wetlands to apparent monocultures of P. arundinacea. The purpose of this study was to determine the effects of P. arundinaceamediated changes in the wetland plant community on avian communities and nesting success. During 2006 and 2007, I studied four diverse sedge wetlands paired with four wetlands dominated by P. arundinacea in the farmland region of southern Minnesota. I measured vegetative structure and composition, surveyed birds year-round via the fixedradius point count technique, and conducted nest searching and monitoring to assess nesting success of Red-winged Blackbirds (Agelaius phoeniceus). Vegetation in wetlands invaded by P. arundinacea was taller and had greater visual obstruction readings than vegetation in sedge wetlands, but sedge wetlands had greater plant species richness and number of woody stems/100 m2 that were < two meters tall. Plant species diversity, litter depth, horizontal heterogeneity, and number of woody stems/100 m2 that were > two meters were not different between habitat types. Bird species richness was greater in wetlands invaded by P. arundinacea during the breeding season but did not differ between habitat types during the non-breeding season. Bird species diversity was not different between habitat types during either season. The abundance of individual species, including rare and listed species, also was not different between habitat types for either season, with one exception. The Ring-necked Pheasant (Phasianus colchicus) was more abundant in wetlands dominated by P. arundinacea during the non-breeding season. Rare species collectively contributed similar percent composition to the bird communities of each habitat type. Furthermore, nesting success and density of nests/10 hectares of Red-winged Blackbirds was not different between habitat types. Results of this study did not indicate that invasion by P. arundinacea has a negative effect on bird communities or nesting success of Red-winged Blackbirds in wetlands of southern Minnesota. The invasion by P. arundinacea does not appear to have altered the structure of wetland vegetation in a way that negatively affects birds and may provide better avian habitat than is currently perceived. Although invasion by P. arundinacea had mixed effects on the plant community in this study, it has had marked negative effects on other native plant communities and is likely to be a continual problem in the restoration and management of wetlands in Minnesota.
Brock R. McMillan
Bradley J. Cook
Date of Degree
Master of Science (MS)
Science, Engineering and Technology
Hutchins, Emily J., "The Effects of Invasion by Reed Canarygrass (Phalaris arundinacea) on Avian Communities and Nesting Success in Minnesota Wetlands" (2011). All Theses, Dissertations, and Other Capstone Projects. 12.
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