It is widely assumed that waterfowl management activities benefit a variety of wetland dependent birds, but few studies have empirically evaluated those benefits or tradeoffs among multi-species management strategies. In particular, marsh birds are an understudied guild of migratory birds of conservation concern that can be valuable indicators of wetland health and may benefit from wetland management for waterfowl. We assessed marsh bird occupancy of wetlands across Illinois to better understand how natural wetland characteristics, management for waterfowl, and surrounding landscape characteristics influence marsh bird occupancy of wetlands.During late spring and early summer 2015–2017, we conducted call -back surveys to assess marsh bird occupancy of wetlands with respect to wetland characteristics and management throughout Illinois. We surveyed marsh birds three times annually at focal sites (i.e., sites selected for their passive or active management for waterfowl), random sites (i.e., emergent, pond, or lake polygons from the National Wetland Inventory), and Critical Trends Assessment Program (CTAP) sites (i.e., randomly selected wetlands concurrently surveyed by the Illinois Natural History Survey’s CTAP). We recorded 3,680 marsh bird detections including nine of ten target species with American coot (Fulica americana; 61.3%) and sora (Porzana carolina; 26.7%) most oftendetected. The odds of detecting marsh birds declined 33.9% (33.0 – 34.9%) each week from the beginning of the survey period. The odds that a marsh bird occupyied a random or focal wetlandsite was 2.29 (0.44 – 6.99) and 5.11 (1.10 – 16.78) times greater than a CTAP wetland, respectively. Focal wetlands had 0.8 (-0.54 – 6.10) times greater odds of being occupied than random wetlands. Moreover, marsh bird occupancy generally increased with wetland complexity. Specifically, sites classified as moderately-low (level 2) and moderately-high (level 5) complex were 9.91 (0.21 – 97.60) and 27.79 (2.05 – 270.56) times more likely to be occupied than monotypic habitats (level 1), respectively. We further analyz ed marsh bird data separately by vegetation association allowing us to further examine patterns of occupancy by marsh bird guild . For example, marsh bird species associated with emergent vegetation occupied wetlands with greater habitat complexity, inundation area, and proportion of habitat classified as dense persistent emergent vegetation, whereas, open-water associated marsh birds were positively related to habitat complexity, and varied among site types and waterfowl management intensities. Under detailed circumstances, waterfowl habitat management positively influenced marsh bird occupancy, yet , not all marsh bird species or guilds responded accordingly. Specifically, open-water associated marsh birds had greater occupancy of focal managed waterfowl sites , whereas, the intensity of waterfowl management and other site characteristicsdetermined the attractiveness of wetlands to marsh birds associated with emergent vegetation. At great levels of waterfowl management intensity, managers control hydrology or mechanically disturb soils or vegetation limiting the growth or persistence of emergent vegetation sought by secretive marsh birds during the spring migration period. Moreover, drainage of wetlands to prepare for spring planting of agricultural grains or to promote early successional vegetation prior to completion of marsh bird migration creates inaccessible habitat and likely drives some of the patterns witnessed. Marsh bird occupancy can be increased on areas managed for waterfowlif practices maintain inundated emergent vegetation through the marsh bird breeding season. Additionally, managers should focus efforts on wetlands in landscapes with limited disturbance, high habitat complexity, large wetland area, and high percent cover of dense persistent emergent vegetation lead to increased marsh bird occupancy rates.The following information is a preliminary thesis chapter addressing the first and third objectives outlined in the scope of work. Analyses addressing the second objective are ongoing and will be reported in full in the upcoming final performance report (on or before 31 March 2019). All results presented at this time are preliminary and subject to change.
|Name||INHS Technical Report 2018 (31)|