Located in northeastern Illinois, the Lake-McHenry Wetlands Complex consists of one of the state's largest concentrations of natural wetlands and glacial lakes, interspersed with rapidly growing suburban communities and business/shopping developments.
Two adjacent counties, Lake and McHenry, contain natural lakes including Grass, Marie and Nippersink along with the Fox River that connects seven other lakes (Bluff, Fox, Pistakee, Channel, Petite, Catherine and Redhead). In addition, the area contains a 44-acre lake within Chain O' Lakes State Park.
Adjoining these lakes in some locations are wetlands of varying degrees of quality. Some high-quality wetlands are preserved by the State, the McHenry County Conservation District and the Lake County Forest Preserves.
The complex supports several breeding wetland species including Least Bittern, Black Tern, Pied-bill Grebe, Sandhill Crane, Common Moorhen, Forster's Tern and Yellow-headed Blackbird.
This site was chosen as an IBA because it met the criteria for breeding Pied-billed Grebe, Least Bittern, Sandhill Crane, Common Moorhen, Forster's Tern, Willow Flycatcher, and Yellow-headed Blackbird.
One threat is the invasion of exotic plants, which includes purple loosestrife and buckthorn in wetlands and garlic mustard, buckthorn and honeysuckle in the woodlands. Another threat is the development of adjacent lands to housing and commerical properties, which reduces foraging opportunities for birds and can alter the hydrology of the wetlands, virtually eliminating nesting habitat for some species such as Yellow-headed Blackbird. This development also creates disturbances for migratory and nesting shorebirds and waterfowl.
Significant natural features in this poorly drained area include glacial landforms, natural lakes and wetlands. Many wetland types are found in this area, such as bogs, fens, seeps and shallow and deep marshes. This site has a large number of Natural Areas and Nature Preserves. The 72 Natural Areas and 34 Nature Preserves include bogs, fens, seeps, marshes, sedge meadows, natural lakes, glacial features and prairies.
Areas within the complex have a large hunting program, camping, boating, equestrian and hiking. Other areas within the complex are managed as an avaian sanctuary with limited deer and waterfowl hunting.