Avian activity and nesting success in Phragmites dominated wetlands

Background/Question/Methods The increasing presence of Phragmites australis in Great Lakes coastal wetlands has raised concerns of habitat degradation and loss of biodiversity in these wetlands. However, few studies have documented the impacts upon biodiveristy due to the invasion and spread of this grass. We monitored two Lake Erie coastal marshes along the south shore of Lake Erie (Huron, OH) to determine the effect of Phragmites australis on avian populations. We selected nine sites based on dominant vegetation type (Phragmites australis (n=3), Typha angustifolia (n=2), Nelumbo lutea (n=3), and mixed emergent vegetation (n=1)). Avian surveys to determine abundance, behavior, and nesting were conducted on a three day rotation from May through August. Results/Conclusions The most abundant bird species observed were Red-winged Blackbirds (Agelaius phoeniceus) and Marsh Wrens (Cistothorus palustris), although several other species, including secretive marsh birds were documented. Our preliminary results indicate that avian abundance was higher in P. australis as a substrate (1196 birds) than in T. angustifolia (333 birds), N. lutea (197 birds), and mixed emergent vegetation (125 birds).  However, the number of nests in P. australis was extremely low (13) compared to T. angustifolia (30), and the proportion of successful nests was low in both P. australis (31%) and T. angustifolia (17%).  Preliminary results suggest P. australis monocultures may serve as habitat sinks in southern Lake Erie coastal marshes due to vegetation characteristics of the monoculture, and T. angustifolia sites may serve as habitat sinks due to extremely high predation rates.  Neither habitat may be able to maintain long-term avian populations.