Abstracts

H.4-1: Wetland suitability for spring-migrating waterfowl in the Midwest

Abigail G. Blake-Bradshaw, Illinois Natural History Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, IL
Joseph D. Lancaster, Illinois Natural History Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, IL
John R. O’Connell, Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, IL
Jeffrey W. Matthews, Department of Natural Resources Environmental Science, University of Illinois at Urbana-Champaign, Champaign, IL
Michael W. Eichholz, Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, IL
Heath M. Hagy, U.S. Fish and Wildlife Service, National Wildlife Refuge System, Stanton, TN

Presented by Abigail G. Blake-Bradshaw - Email: ablakebradshaw@gmail.com

Wetland-dependent bird populations may be limited by suitable habitat in regions where loss and degradation of wetlands is pervasive, such as in the midwestern United States. Suitability of stopover wetlands used by wetland-dependent birds during spring migration may be linked to survival, body condition, and recruitment during the subsequent breeding season. However, available spatial datasets, such as the National Wetlands Inventory (NWI), may overestimate habitat availability if total wetland areas include areas which are unsuitable for use by wetland-dependent species. During springs 2015–2017, we assessed proportional coverages of suitable wetland vegetation and inundation conditions relative to the NWI for waterfowl and other waterbirds in Illinois. We modeled vegetation and inundation cover as a function of local and landscape characteristics during spring migration for dabbling ducks. Suitable wetland conditions comprised a small portion of NWI polygons. Shallowly inundated wetlands (<45 cm) suitable for foraging by dabbling ducks comprised 29% of NWI area in Illinois during spring migration. Approximately 37% of emergent NWI wetland area was shallowly inundated, whereas only 25% of forested wetland area was shallowly inundated. Highly interspersed vegetation and open water (i.e., hemi-marsh) was <1% of wetland area surveyed. Wetlands with greater vegetation complexity and connectivity to other wetland types had the greatest suitable area. We recommend conservation planners consider adjusting their estimates of wetland availability from spatial databases, such as NWI, when used to evaluate wetland supply on the landscape since significant proportions of forested and emergent wetland area was not flooded, were flooded at unsuitable depths, and/or wetlands lacked vegetation resources to provide substantial food resources.