Marsh Bird Use of Wetlands Managed for Waterfowl in Illinois

Conservation planners often assume waterfowl management activities benefit other wetland-associated birds, but few studies have quantified benefits among management strategies for multiple species. Overall, marsh birds are an understudied guild that can be valuable indicators of wetland conditions. Our objectives were to 1) compare marsh bird use of restored and natural wetlands, 2) determine characteristics of wetlands and the surrounding landscape that influence marsh bird use of wetlands, and 3) compare marsh bird use of wetlands managed for waterfowl across a continuum of management intensities. During late spring and early summer 2015–2017, we conducted call-back surveys to quantify marsh bird use of wetlands and assessed wetland quality using a modified version of the Ohio Rapid Assessment Method (ORAM) throughout Illinois. We conducted surveys on wetlands managed primarily for waterfowl (focal), wetlands selected randomly from emergent NWI polygons across natural divisions in Illinois (random), and those surveyed through the Critical Trends Assessment Program (CTAP). We conducted three rounds of surveys at each site and followed the standardized North American marsh bird monitoring protocol. Preliminary analysis suggests differences in detections across management intensities, percent flooded, and water depth. Average detections (birds/survey/site) were greatest in survey round one (x-bar = 14.5, SD = 46.3), and less in round two (x-bar = 7.5, SD = 28.6) and three (x-bar = 2.2, SD = 5.7). Average detections (birds/survey/site) were greatest in focal sites (x-bar =21.7, SD = 54.7), followed by random (x-bar = 2.9, SD = 9.0) and CTAP sites (x-bar = 0.4, SD = 0.8). We used logistic regression in an occupancy modeling framework to evaluate potential effects of environmental factors on probability of detection and habitat use. Our goal is to provide management recommendations that will encourage marsh bird use and increase overall wetland quality.