Bergman is a small isolated slough at the southwest portion of the 14,000-acre Palos Preserves, a series of lakes, sloughs and woods carved thousands of years ago by melting glaciers. These habitats are owned and managed by the Cook County Forest Preserve District.
Bergman Slough is south of Route 83 and just east of Will-Cook Road, which divides Cook and Will Counties.
After more than 50 years of absence as a breeder in Illinois, an Osprey was observed building a nest at Bergman Slough the summer of 1996. Breeding was not successful that year nor in 1997, but from 1998 through 2000 and then again in 2003, a pair of Ospreys fledged young at Bergman Slough. Ospreys also set up nesting in 2004 and 2005 at Bergman, but were not successful.
Since the return of the Osprey to Illinois as a nesting species in 1996, the species has also attempted nesting in another northern Illinois location as well as at several locations in southern Illinois. Successful nesting was confirmed in 2004 on a nesting platform at Carlye Lake in southern Illinois and at Powderhorn Marsh in the Lake Calumet region in northern Illinois. In addition, a pair of Osprey successfuly bred at Banner Marsh State Fish & Wildlife Area in 2006. In 2004, a pair attempted but failed to complete nesting at Mermet Lake in extreme southern Illinois. In 2007, the Illinois Department of Natural Resources reported there were four active Osprey nests in the state, one at Powderhorn in Cook County, whose nest failed, one at Banner Marsh State & Fish Wildlife Area, where two young fledged, and a pair each at Lake Carlyle and Lake Mermet, although the success of these nests is unknown. It is likely this species will continue to breed and possibly expand very slowly in the state, especially since it has been successful, which gives it the impetus to return each year. Bergman Slough was chosen as an IBA because it met the criteria for breeding Osprey.
Bergman Slough is an open water wetland that often freezes over in winter.