Effects of Off-channel Wetland Restoration on Breeding Bird Communities

Channelization of rivers and streams threatens bottomland forest bird communities because it results in channel incision and can lead to the formation of lateral gullies that connect streams to adjacent wetlands and drain the wetlands when water levels in the stream drop below flood stage. These adjacent forested wetlands may fill during spring floods and be attractive breeding habitat for birds, but the unnaturally rapid draining of the wetlands early in the breeding season may expose some birds to high rates of nest predation. I studied how the hydrologic restoration of off-channel wetlands (plugging gullies that drain off-channel wetlands) affects the diversity, abundance, and nesting success of birds breeding within forested wetlands within the Cache River watershed in Illinois. I compared surface area, water depth, bird diversity, bird densities, and nesting success between treatment (gully plugs added) and control (gully plugs not added) wetlands pre- and post-treatment. During the breeding season of birds, treatment wetlands retained more surface area and greater depths of water compared to control wetlands. Bird diversity was unaffected by the installation of gully plugs. The density and nesting success of prothonotary warblers (Protonotaria citrea) was higher in treatment wetlands than in control wetlands. Other species associated with forested wetlands (yellow-throated warblers, Dendroica dominica; wood ducks, Aix sponsa; and yellow-crowned night-herons, Nyctanassa violacea) also increased in number within the treatment wetlands. Documenting changes in the bird community in response to this conservation action provides a means to measure the success of restoration activities in the Cache River watershed and inform conservation plans and restoration efforts in other bottomland forest ecosystems.