Effects of hydrologic restoration on birds breeding in forested wetlands

Abstract

Channelization of rivers and streams threatens bottomland forest bird communities because it can lead to the formation of lateral gullies that connect streams to adjacent wetlands and unnaturally accelerate the draining of wetlands, potentially exposing 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 flooded 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. 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.