A black crowned night heron in a marsh.
Black crowned night heron Black-crowned night heron. © Mark Godfrey/TNC

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South Side Forest Preserve site gets government-backed water control structure

Eggers Grove’s water levels affected by climate, development—too high for many birds, plants to thrive.

Chicago, IL

Straddling the Illinois-Indiana border is Eggers Grove, a 240-acre woodland and wetland area that attracts people from all over the county and is also a haven for migrating birds from around the country. Since urban development cut off the site from Lake Michigan, the wetland no longer has a natural fluctuation in water levels. This week, construction begins on a new water control structure that will allow the Forest Preserves to drain and adjust the water levels in the area on a more natural cycle, like it would have originally done in conjunction with Lake Michigan levels.

Scientists and specialists from Forest Preserves of Cook County (FPCC)—which owns and operates Eggers Grove—The Nature Conservancy and Audubon Great Lakes noticed that drainage infrastructure out of the marsh had become degraded and non-operational and choked with common reed and silt, effectively damming the marsh and creating unusually long-lasting, high water levels.

“These artificially high water levels make the area uninhabitable for many birds that once nested or stopped to rest and refuel during their migratory travels,” said Brad Kasberg, wetland restoration manager at Audubon Great Lakes in Chicago. “Native bird species that were once abundant in our region, such as black-crowned night-heron and least bittern, have been in steep decline and are now endangered or threated. Restoring the natural ability of the marsh to fill and drain is absolutely necessary to save these birds.” 

As a result, the cohort of agencies applied for and received Great Lakes Restoration Initiative (GLRI) funding to install a water-control structure which will allow FPCC and partners to draw the water down to dry out sediment and allow native plant seeds to germinate. GLRI dollars are supplied by the US Fish and Wildlife Service to the National Fish and Wildlife Foundation, which eventually doles it out to Great Lakes conservation groups such as Sustain Our Great Lakes (SOGL). TNC was awarded $100,000 via SOGL toward the water structure project while $65,000 came from Great Lakes Audubon, and $234,000 from the Forest Preserves.

The new water control structure will allow the Forest Preserves to replicate the conditions of the local wetland system when it drained into nearby Wolf Lake, before development—including the construction of a Nike missile site in the 1950s—changed water flow patterns. Three manual gates will be used to adjust water levels to maintain a mix of open water and emergent vegetation, to dry out sediment, and to allow native plant seeds to germinate.

The water-control structure is the latest step in ongoing work to restore the wetlands at Eggers Grove, which has included support from the USDA Natural Resources Conservation Service, Illinois Department of Natural Resources Coastal Program, and funding and staff expertise from the Field Museum. Eggers is one of the few remaining wetlands in the Calumet region, a major migratory route for many kinds of wildlife.

“We all have seen some incredible results from water control structures in our respective organizations and know this is a viable way to help manage this amazing city gem for both people and nature,” said John Legge, Chicago conservation director at The Nature Conservancy and lead author of the SOGL grant that helped fund the project. “This is also yet another example of how GLRI dollars, along with private support, can be used to improve the lakes, coasts and surrounding communities that border and, in turn, impact the overall health of the Great Lakes. It is imperative to have support of policies that allow public-private relationships to flourish to protect the Great Lakes’ wildlife and economy that both depend on the water’s health.”

While GLRI funds have been threatened in recent years, it continues to be a bi-partisan stronghold issue. Calls to protect the region and its waters from climate impacts, overabundance of invasive species and many other issues have increased as the region’s $7 billion economy depends more and more on the health of the Great Lakes system.

“Biodiversity is as critical in aquatic areas as it is on land in sustaining healthy natural areas,” said Chip O’Leary, the deputy director of resource management for the Forest Preserves. “In our urbanized landscape, it takes new techniques to restore habitats. This water control structure will allow vegetation that is native to this type of hemi-marsh to thrive, and in conjunction with the right water levels, that will attract migrating birds and other wildlife.”

At nearby Big Marsh, a southeast side Chicago Park District site with a water control structure, Audubon monitoring shows that following the structure’s construction, the number of focal marsh bird species observed more than doubled. Between 2017 and 2018 swamp sparrows and Black-crowned night heron re-established themselves, as Yellow-crowned night heron observations increased at the site.

“We are anticipating great results, similar to Big Marsh,” added Kasberg. “There are many factors that can impact migration in this region, but we are excited to use this data to put a number to the species count, but also help us create long-term cooperative conservation plans for the Calumet and Great Lakes conservation community.”

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 72 countries, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit www.nature.org or follow @nature_press on Twitter.