The wetlands, prairies and wooded areas that still exist in the Lake Calumet region provide food and shelter for many species of birds throughout the year. Over 200 species of birds occur in the Lake Calumet area, many of which do not nest anywhere else in northeastern Illinois.
The wetlands serve as an invaluable staging area for hundreds of species of birds that need to rest and refuel as they follow a major migratory route along Lake Michigan's shores during spring and fall migrations. The wetlands also provide valuable breeding habitat for many state endangered and threatened species. In fact, the state endangered Black-crowned Night Heron colony at Lake Calumet is the largest rookery for this species in the state and one of the oldest.
The abundance of birds is due partly to the proximity of the Lake Calumet wetlands to the south end of Lake Michigan and the habitat variety the region offers for breeding, migration, foraging and resting. The wetlands provide breeding habitat for herons, egrets, moorhen and rails, as well as a variety of waterfowl, such as Blue-winged Teal, Mallard, and Wood Duck. Lake Calumet and the surface waters that surround it also provide the very specific habitat needed by shorebirds. A large contingent of shorebirds representing at least 39 different species, including the Greater and Lesser Yellowlegs, Dunlin Curlew and Pectoral Sandpipers, and American Avocet, stop in the area during migration, particularly during the fall when water levels are low and the sand bars and mud flats are exposed. Finally, the prairies, open meadows and woodlands provide habitat for such species as song, savannah and vesper sparrows, Great-horned Owl, Red-tailed Hawk, Eastern Bluebird, Eastern Meadowlark, and Gray Catbird.
The region encompasses several types of ecosystems, including some very high quality sites that have never been plowed or filled in, such as the sand prairie in Powderhorn Lake Forest Preserve. This site is one of seven in the region that are listed on the state of Illinois Natural Areas Inventory, and one of the two sites dedicated as a State Nature Preserves, the highest form of preservation in the state of Illinois.
According to "Wetlands Plants of the Calumet Region", compiled by Gerould Wilhelm in 1992: Altogether, 762 species exist in the region including 52 species of trees, 64 shrubs, 17 vines, 19 ferns, 464 forbs, 62 grasses, and 85 sedges. There are 152 additional species believed to be adventive in the area since settlement. Nearly 60 percent of the native species are classified by the U.S. Fish & Wildlife Service as wetland plants.