Into the Wetlands We Must Go!

Waterfowl undergo extensive migrations between breeding grounds throughout Canada and the northern U.S. and wintering areas in the southern U.S, and southward. During migration, waterfowl rely on a network of wetlands to rest and refuel. These wetlands are critical, since research suggests that stopover and pre-breeding activities may affect survival and future breeding success. However, management for migratory species can be difficult since birds do not adhere to jurisdictional boundaries (e.g., states, countries), making it difficult to study habitat availability and quality throughout their annual cycles.

The Midwest landscape is highly fragmented and only a few wetlands dot a landscape dominated by agriculture and urbanization. Despite losing approximately 85 percent of its historic wetlands, Illinois still provides important stopover habitat for waterbirds during migration, and even provides breeding habitat for some species (e.g., wood ducks, mallards). However, scientists need to know how much and what kinds of wetlands are needed to ensure that the best habitats for the greatest numbers of birds are restored and protected.

Currently, agencies and organizations tasked with care of migratory waterbird populations lack information regarding the quality of available wetland habitat, such as water depth, vegetation cover and surface water seasonality. This project, funded by the Federal Aid in Wildlife Restoration Pittman-Robinson Act through the Illinois Department of Natural Resources, seeks to provide better estimates of habitat quantity and quality during spring migration, summer breeding and fall migration periods. We focused on three guilds of waterbirds during these periods, including waterfowl during spring, secretive marsh birds during summer and shorebirds during fall.

What constitutes “quality” wetlands for waterbirds? Depending on the species of interest, habitat preferences and requirements can vary greatly. However, the presence of water is paramount, specifically shallowly inundated areas where waterbirds can access forage such as mussels, invertebrates and seeds.

Additionally, submersed, floating-leaved, and emergent vegetation, such as pondweeds or cattails respectively, are critical for forage and cover. Many species, such as dabbling ducks, prefer areas of emergent vegetation interspersed with open water, known as “hemi-marsh.” However, many Illinois wetlands may not provide suitable vegetation, or may be dry during critical periods.

Our team surveyed wetlands across the state of Illinois during spring, summer and fall 2015–2017, contrasting wetland quality across seasons and recording waterbird use. Some preliminary results indicate that approximately 10 percent of emergent and forested wetlands are completely dry and thus not readily usable by spring migrating waterfowl, and wetlands often lacked flooded emergent vegetation and hemi-marsh. We hope the data will provide useful insights and baseline information on the quality of available wetland habitat in different regions of Illinois.

While slogging through wetlands can be strenuous work, not for the faint-of-heart, the waterbirds and other wildlife are worth it.