Dramatic Swings in Great Lakes Water Levels Make Life Tough for Birds

On Wisconsin's Cat Islands and around the region, wildlife managers are working to create avian safe harbors from the climate-fueled fluctuations.

Decades ago the Cat Island chain in Lake Michigan’s Green Bay was a bird haven. The archipelago sheltered waterfowl-rich wetlands from waves and provided habitat for an array of migratory shorebirds and the greatest diversity of colonial nesting species of any Great Lakes islands. Then, in the 1970s, severe storms coincided with extremely high lake levels, battering the islands into oblivion and driving many birds to abandon the site.

This year the lake rose again, to near-record highs. And yet, birds flourished, thanks to a project that’s rebuilding the islands. Gulls, terns, and other colonial nesters were back. So were more than 30 shorebird species, including the threatened rufa Red Knot and the endangered Piping Plover. Drawn to the newly built high ground, plovers returned in 2016 to nest in Lower Green Bay for the first time in 75 years. This past summer 15 chicks scuttled across the Cat Island sands, a promising foothold for a fragile population. “Frankly, I was not expecting this kind of success,” says Bob Howe, a University of Wisconsin-Green Bay ecologist involved in the restoration. “The results have been nothing short of amazing.”

But Piping Plovers didn’t fare as well elsewhere on the Great Lakes, where the species has been slowly recovering from near extirpation. “A handful of sites where we normally get breeding plovers didn’t see any this year, most likely because of the high waters,” says Vince Cavalieri, who until recently coordinated Great Lakes plover work for the U.S. Fish and Wildlife Service.

Just six years ago, lakeside communities faced the opposite problem: extremely low water. Fluctuation is normal on these inland seas, but scientists say the region should prepare for more drastic highs and lows as climate change alters natural precipitation and evaporation patterns. As they embark on this era of increasingly erratic lake levels, wildlife managers are working to ensure that habitat projects offer birds refuge as conditions shift.

One important tool at their disposal is the Great Lakes Restoration Initiative (GLRI). Signed into law in 2009, the federal program has pumped nearly $2.5 billion into more than 4,800 projects to clean up pollution, remove invasive species, and restore habitat. (Read more about the initiative's impact below.) Birds have been major beneficiaries, including on the Cat Island chain.

Using $1.5 million from the GLRI, the U.S. Army Corps of Engineers is rebuilding the islands with sediment dredged from the shipping channel at the Port of Green Bay. Since construction on the 30-year project began in 2012, the Corps and partners have completed a 2.5-mile causeway and partially rebuilt two of three islands. Along with re-establishing habitat that remains high and dry, the completed project will help to shelter and restore more than 1,200 acres of wetlands at the bay’s southern end.

In the past couple of years, water levels seem to have reached the upper limit, even for marsh-nesting species.

Although it threatens species like plovers, high water is generally a good thing for other birds; in research conducted as waters rose from 2013 to 2018, Tara Hohman, an Audubon conservation science associate, observed an increase of 45 percent or more in the abundance of some marsh birds, including species like Common Gallinule, Least Bittern, and Pied-billed Grebe that have been in steep decline regionally.

Yet in the past couple of years, water levels seem to have reached the upper limit, even for marsh-nesting species—especially those that prefer a mixture of open water and emergent vegetation, says Erin Giese, a senior research scientist for the Cat Island project. As high water has inundated wetlands, some marsh birds have begun to feel too submerged for their liking. “At some point, it’s going to wash out all of the wetland and there’s going to be no bird habitat, period,” says Giese, who has already seen this occur in various spots around Green Bay.

To help buffer bird populations from these extremes, Audubon Great Lakes and others are outfitting wetlands with water-control structures, funded in part through the restoration initiative, that can hold back water or release it as needed. They finished work on one such project in October at southeast Chicago’s 240-acre Eggers Grove Marsh. It involves a system of gates that manually open and close at three locations, reestablishing a connection with Wolf Lake and Lake Michigan that was severed by development. The gates allow managers to produce a more natural rhythm of changing water levels that creates better wetland habitat for the region’s once abundant marsh birds, including Least Bittern and Virginia Rail, as well as its diverse migrating bird population. 

Audubon Great Lakes is also hoping that diked wetlands can help protect the region's drastically declining Black Tern population from extreme lake levels. In the past two years of high waters, the number of Black Tern breeding pairs dropped from a consistent 350 or so to below 200 at Michigan’s Saint Clair Flats State Wildlife Area, at least partly due to the flooding of the mudflats on which the marsh birds nest. In response, Audubon and partners plan to entice terns and waterfowl to use the more protected habitat behind the dikes by cutting through stands of cattails and phragmites there that have grown too thick for the birds to breed in. 

Such efforts to protect and restore coastal habitat will help ensure birds some stability in an increasingly unstable future. “The coastal areas of the Great Lakes are disproportionately important for birds, but also under the greatest threat in our region because of climate change,” says Nat Miller, acting executive director of Audubon Great Lakes. “If we can create new areas, then we’re adding to important pinch points for species like Piping Plovers and marsh birds that are really struggling to find adequate spaces to breed.” As the growing flocks on the Cat Island chain attest, investments in climate-resilient bird habitat quickly pay off.


Restoration Gets Results

The Great Lakes Restoration Initiative (GLRI) has boosted the environmental health of a region with 84 percent of North America’s surface fresh water, more than 30 million people, and over 350 bird species. The lakes still face serious challenges, such as pollution and invasive plants and animals, but the cleanup, at its 10-year mark, has made significant strides.

Acres of coastal wetlands protected or restored through the initiative. Among them are 1,000 acres alongside Lake Erie in northwest Ohio—the world’s unofficial warbler capital for its mind-blowing spring migration—converted from drained farmland to a marshland park with help from a $2.8 million grant.

Percentage increase in nesting pairs of Great Lakes Piping Plovers. GLRI-funded habitat projects have helped to secure the population’s rebound to 71 pairs in 2019 from 12 pairs in 1990. In 2017, Piping Plovers nested on all five lakes for the first time since 1955.

Approximate acreage covered by projects to control invasive species. The program includes efforts to combat invasive mussels suspected of helping to spread avian botulism, a disease that has killed more than 100,000 Great Lakes birds in the past two decades.

Number of indicators of ecological harm eliminated by cleanup work at 23 toxic Areas of Concern. These include bird deformities, beach closings, and restrictions on eating fish. That’s seven times the number of such issues resolved in the 22 years prior to the initiative’s launch.

This story originally ran in the Winter 2019 issue as “Fresh Water in Flux.” To receive our print magazine, become a member by making a donation today.​