Iroquois State Wildlife Area is situated in a low glacial outwash plain associated with the Kankakee River Valley near
Beaverville, Illinois, about 80 miles south of Chicago.
The initial acquisition of land occurred in 1944 to protect the declining prairie-chicken population in Illinois. However, the prairie- chickens did not survive.
The State purchased an additional 560 acres in 1984. Known as the Hooper Branch Savanna, 480 acres of this parcel are considered the largest single tract of rare native savanna remaining in Illinois.
The Iroquois State Wildlife Area exhibits some of the finest and most extensive prairie marsh and sand dune vegetation remaining in Illinois. The dry sand ridges are dominated by black oak forest.
Lower lying areas range from dry prairie to marsh. Dominant grasses on dry prairie areas contain little bluestem and switch grass. Grasses such as big bluestem, Indian grass, little bluestem, and switch grass dominate the mesic prairie. Areas of wet prairie are indicated by bluejoint grass, cord gras, and sedges. Several boggy areas contain plants seldom encountered elsewhere in Illinois. Among these are blueberry, huckleberry, hardhack, marsh marigold, colic root, sundew and primrose violet. Hooper Branch Savanna occupies the edge of former Glacial Lake Watseka. Fourteen thousand years ago this lake formed between moraines damming up glacial meltwaters. The soils of Hooper Branch Savanna are sandy, having derived from beach and nearshore sand deposits exposed to wind action. A dune and swale topography developed, which is quite noticeable today. Savanna developed on the dry dune ridges while shrub prairies and mesic sand prairies developed in the wetter swales.
Several bird species that are either near the southern (Virginia Rail, Common Snipe, Swamp Sparrow) or northern (Northern Mockingbird, White-eyed Vireo, Summer Tanager, Blue Grosbeak) edge of their breeding ranges, or are rarely found anywhere in the state as a breeder, nest at the Iroquois County Conservation area. Summer records exist for Long-eared Owl, Blue-headed Vireo and Cerulean, Hooded and Chestnut-sided Warblers. Regular breeders include Least Bittern; King and Virginia Rails; Northern Bobwhite; Broad-winged Hawk; Whip-poor-will; Red-headed Woodpecker; Sedge Wren; Veery; White-eyed and Bell?s Vireos; and Grasshopper, Swamp, Henslow?s and Lark Sparrows. Migrating sparrows including LeConte?s and Nelson?s Sharp-tailed.
This site was chosen as an IBA because it met the criteria for breeding Red-headed Woodpecker, Sedge Wren, and Henslow's Sparrow.