Energetic implications of floodplain wetland restoration strategies for waterfowl

Abstract

Modifications of the Illinois River and associated tributaries have resulted in altered hydrologic cycles and persistent river‐floodplain connections during the growing season that frequently impede the establishment of hydrophytic vegetation and have reduced value for migratory waterfowl and other waterbirds. To help guide floodplain restoration, we compared energetic carrying capacity for waterfowl in two wetland complexes along the Illinois River under different management regimes during 2012–2015. The south pool of Chautauqua National Wildlife Refuge (CNWR) was seasonally flooded due to a partial river connection and managed for moist‐soil vegetation. Emiquon Preserve was hydrologically isolated from the Illinois River by a high‐elevation levee and managed as a semipermanently flooded emergent marsh. Semipermanent emergent marsh management at Emiquon Preserve produced 5,495 energetic use‐days (EUD)/ha for waterfowl and other waterbirds across wetland cover types and years, and seasonal moist‐soil management at CNWR produced 6,199 EUD/ha in one of 4 years. At Emiquon Preserve, the aquatic bed cover type produced 9,660 EUD/ha, followed by 5,261 EUD/ha in moist‐soil, 1,398 EUD/ha in persistent emergent, 1,185 EUD/ha in hemi‐marsh, and 12 EUD/ha in open water cover types. At CNWR, the annual grass and sedge cover type produced 7,031 EUD/ha, followed by 5,618 EUD/ha in annual broadleaf and 1,305 EUD/ha in perennial grass cover types. Restoration of floodplain wetlands in isolation from frequent flood pulses during the growing season can produce hemi‐marsh and aquatic bed vegetation communities that provide high‐quality habitat for waterfowl and which have been mostly eliminated from large river systems in the Midwest, U.S.A.

Marsh bird occupancy of wetlands managed for waterfowl in the Midwestern USA

“…Managed wetlands with later drawdowns (e.g., June-July) and those with less frequent drawdown schedules (e.g., 1 in 3-5 years) have greater potential for marsh bird occupancy, but more work is needed to understand the impacts of management on nest success and survival of marsh bird species throughout the annual cycle [40,53,54]. Our work reinforces previous findings that wetlands with greater hydrological and vegetation complexity that produces dense, emergent vegetation support greater marsh bird occupancy in the Midwest [6,[55][56][57][58][59]. Previous work on breeding marsh bird habitat has focused on two scales-the surrounding landscape and local/point scale.…”

“…Increased marsh bird use of wetlands can be achieved within a mosaic of wetland conditions across a wetland complex, by managing a subset of units to increase coverage by dense, persistent emergent vegetation by maintaining surface water during the growing season for several consecutive years. Wetlands with dense emergent vegetation will eventually need to have succession reset, and this can be done as a part of multi-year hydrology management strategies while also providing waterfowl habitat in unity with regional waterfowl management plans [55,57,58]. Creating or managing for emergent marshes with semi-permanent water regimes that provide a mosaic of emergent vegetation, open water, and submersed aquatic vegetation can provide abundant food for waterfowl while promoting use by marsh birds [55,58] Supporting information S1 Appendix.…”

Variation in True Metabolizable Energy Among Aquatic Vegetation and Ducks

“…Our study greatly expanded the list of available TME N estimates of submersed aquatic vegetation for waterfowl for use by wetland managers and conservation planners. These estimates can be incorporated into conservation planning exercises to help estimate the energetic carrying capacity of semi‐permanent and permanent wetlands where submersed aquatic vegetation occurs (Gross et al 2019, McClain et al 2019). Although all 6 species of submersed aquatic vegetation provided a positive energy source for either mallards or gadwall, only coontail and Canadian waterweed provided energy to both.…”

“…Most waterfowl primarily feed in wetlands where seeds, tubers, aquatic macroinvertebrates, and vegetative resources from natural hydrophytic vegetation comprise available food resources (Stafford et al 2011, Hagy and Kaminski 2012, McClain et al 2019). Despite relatively similar foraging habitat conditions across the non‐breeding period, >20 species of waterfowl common in the midcontinent of North America generally partition themselves among a seemingly finite pool of shared food resources (DuBowy 1988, Brochet et al 2011).…”

Visibility Bias of Waterbirds During Aerial Surveys in the Nonbreeding Season

“…Since the early twentieth century, floodplain wetlands were modified, degraded, and eliminated by anthropocentric events including the creation of drainage and levee districts, navigational dams, sedimentation from agricultural runoff, and the diversion of the Chicago Sanitary and Shipping Canal into the Illinois River (Havera 1999). By the time of our study, much of the waterbird habitat in the IRV was comprised of open‐water wetlands devoid of persistent and submersed aquatic vegetation (Havera 1999, Stafford et al 2010) and, with increasing frequency, nonpersistent emergent vegetation (Lemke et al 2017, McClain et al 2018). Persistent and submersed aquatic vegetation was only abundant on a small number of wetlands that were disconnected from the Illinois River (Hine et al 2017, Lemke et al 2018).…”