Abstracts

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

Habitat conditions during migration likely influences body condition and subsequent recruitment of some waterbird species and during the breeding period. However, relatively little is known about relationships between habitat characteristics and waterbird use during spring migration, despite the implication that habitat during spring migration is likely limiting in the Midwest, USA. We used aerial surveys and ground assessments of polygons included in the National Wetland Inventory to identify species-habitat relationships of waterfowl in Illinois during spring migration 2016–2017. We mapped surface water inundation, visually estimated vegetation cover, and assessed wetland management and anthropogenic stressors of all NWI polygon area included in 100–120 25-ha plots each year. Local wetland hydrological and vegetation cover were the most important predictors of dabbling duck and other waterbird densities. Dabbling duck density increased 34.8% and other waterbird density increased 44.6% for every 10% increase in the proportion of wetland areas inundated by surface water. Furthermore, dabbling duck density increased 26.5% for every 10% increase in the proportion of shallow (<45 cm) surface water. Dabbling duck and other waterbird density was negatively related to woody vegetation cover, which could be due to multiple factors including perceived risk associated with more vegetated wetlands or potentially limited food availability. While many factors influence waterbird use and selection, this study emphasizes the importance of providing surface inundation and regions of shallow water during spring migration in Illinois. Restoration efforts should incorporate controllable hydrology and potentially avoid instances where hydrology is largely unregulated in large river floodplains.