Rend Lake is located between Mt. Vernon and Benton, just off Interstate 57.
The U.S. Army Corps of Engineers created Rend Lake in 1965 by damming the Big Muddy River to control flooding as well as to conserve wildlife. The result is a 40,000-acre complex including the 19,000-acre lake with a 5,000-acre waterfowl refuge at the north end. Surrounding the lake are 162 miles of shoreline with 21,000 acres of public land.
These lands contain woods including a 1,000-acre sycamore/maple forest as well as moist soil units and mudflats with water levels that change depending on the season and man-made manipulation.
The mudflats and moist soil units provide migratory habitat for nearly all the shorebirds documented in Illinois as well as copious wading birds.
Since Rend Lake is on some of the flattest land in southern Illinois, not much of a drop in the lake is needed before an open area of mudflats is created. A one-inch drop in the water level can expose acres of new flats, prime habitat for shorebirds.
Thirty-five species of shorebirds including the Buff-breasted Sandpiper and the rare Hudsonian Godwit, American Avocet, Red Knot and Red-necked Phalarope have been documented at Rend Lake. In addition, large numbers of more common shorebird species such as Pectoral, Least and Semipalmated Sandpipers and yellowlegs use the mudflats here. Several thousand shorebirds can be seen in one day at the Ward Branch as well as at the Nason Wildlife Refuge, both within Rend Lake. The Nason Wildlife Refuge also provides habitat for Bald and Golden Eagles, Peregrine Falcon and copious numbers of Ross's Goose, Greater White-fronted Goose and American White Pelican during migration.
Waterfowl also find refuge at Rend Lake. Snow Geese in the tens of thousand use the lake as a stopover and sometimes wintering site. They feed along with other waterfowl in surrouding food plantings provided by the state as well as spilled grain from private landowners.
In late fall and early winter, as many as 30,000 Mallards, 3,000 Ring-necked Ducks, 1,300 Canvasbacks and 500 Gadwall have been counted at Rend Lake in a single day. In spring, observers have seen 500 Northern Shoevelers and 250 Redheads in one day.
Shallower water areas around the lake, especially at the north end offer feeding habitat for various waders including Great Egret, Little Blue Heron, Great Blue Heron and occasionally the rare Glossy Ibis.
Tens of thousands of neotropical migrants as well as hundreds of thousands of passerines, especially swallows, use the lake and surrounding lands for feeding and resting during migration.
Rend Lake is significant because most shorebird species in the world are declining in numbers and some are even becoming endangered or extinct. Habitat loss is one of the main reasons for this decline. Providing habitat for shorebirds at places like Rend Lake is one key to their recovery.
This site met the criteria as an IBA for congregations of waterfowl.