The 1,800-acre Forest Glen Preserve is located seven miles east of Westville on County Highway 5 in Vermilion County, centrall Illinois.
The preserve is characterized by two major forest types, oak-hickory and beech-maple. Forest Glen is one of the higher quality tracts of old-growth forest in Vermilion County.
Within the preserve are four registered Illinois Nature Preserves, Duffin Woods, 200 acres; Forest Glen Seep, 11 acres; Howard's Hollow Seep, 30 acres; and Doris L. Westfall Prairie, 40 acres.
Forest Glen also has a 22-acre restored oak savanna.
Ten Vermilion County residents succeeded in getting a referendum passed in February 1966 to establish a Vermilion County Conservation District; the first parcel of land they purchased was the Forest Glen Preserve.
Spring migrants including up to 36 species of warblers pass through Forest Glen each year; at least 14 of these warbler species remain to breed. These include Worm-eating, Yellow-throated, Blue-winged, Cerulean, Kentucky, Prothonotary, Yellow and Prairie Warblers, along with Northern Parula, American Redstart, Louisiana Waterthrush, Yellow-breasted Chat and Ovenbird.
Small numbers of breeding grassland species include Sedge Wren, Henslow's Sparrow, Eastern Meadowlark and Dickcissel.
In addition, Pileated Woodpeckers, Wild Turkeys and Whip-poor-wills breed in the woodlands along with Red-shouldered and Broad-winged Hawks (rare), Barred Owl, Wood Duck, American Woodcock, Veery (rare), Wood Thrush, Acadian Flycatcher, Carolina Wren, Scarlet Tanager, Summer Tanager, Black-billed Cuckoo and Yellow-billed Cuckoo.
In the grasslands, Henslow's, Savanna and Grasshopper Sparrows can be found nesting, along with Dickcissel and Eastern Meadowlark. Shrublands attract breeding White-eyed and Bell's Vireo, Orchard Oriole and Willow Flycatcher.
Occasionally, Long-eared, Short-eared and Northern Saw-whet Owls spend the winter at Forest Glen.\
This site was chosen as an IBA because it met the criteria for Migrants.
Forest Glen contains one of the finest examples of old-growth forest in Vermilion County. Oak-hickory and beech-maple forests dominate. This is about the farthest north and west in Illinois that native beech forests grow. The Doris Westfall prairie is Illinois' first restored habitat to be dedicated a state nature preserve.
Four dedicated Illinois Nature Preserves exist within Forest Glen. Trails go through many forested areas. Picnicking, camping restricted to edges and more open areas.
Nest boxes for bluebirds are monitored each year. Many years of data on nesting species have been collected.