Predation risk at marsh bird nests as a result of water-level manipulations at Emiquon Preserve

Wetland-obligate marsh birds are a group of birds that are associated with complex vegetated habitat interspersed with open water that provides protection from predators and space to forage. Unfortunately, marsh bird populations are experiencing declines worldwide, and these are believed to be driven by wetland lossand degradation, something that is characteristic to the heavily altered landscape of Illinois. Illinois originally had an estimated 8.9 million acres of poorly drained hydric soil, however by the 1980s, 90% of this wetland acreage was lost due to drainage for agricultural expansion and urbanization. Proper management of the remaining wetland habitat is believed to be the solution for mitigating further marsh bird losses. Emiquon Preserve manages their wetland habitat through water-level drawdowns that mimic natural floodplain pulses. These drawdowns are beneficial for a variety of wetland species, but there are concerns they may be increasing predation risk at marsh bird nests because the drawdowns are initiated after marsh birds have begun nesting. Knowledge on the effects of water-level manipulation for nesting marsh birds is limited, and we are particularly interested in learning more about the effects water drawdowns have on nest success and predator access to nests. In 2020, we searched suitable habitats (hemi-marsh, dense emergent) and located marsh bird nests (Least Bittern, Common Gallinule, American Coot, Black-crowned Night-Heron) (n=88) at varying water depths. We set up continuously recording cameras at a subset of nests (n=52) to record predators at the nests and we revisited the nests throughout the season to document their fate. We found that nests in shallow water and closer to the water’sedge faced an increased risk of predation by mammals, and intense dewatering as prescribed by moist soil management may be exacerbating predation risk at marsh bird nests.