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On the west side of the river in the Thatcher unit a remnant prairie exists in which the state-endangered small sundrops (Oenothera perennis) grows. In Thatcher Glen the state-endangered nodding trillium (Trillium cernuum) was recently discovered. The GAR and Thomas Jefferson units contain floodplain forest and a mesic oak savanna having a large inventory of native Illinois plant species - indicating that this area is a high quality natural area of the Chicago region. At least 45 bird species are nesting residents in this extensive forest habitat. They include the wood thrush, ovenbird, crested flycatcher, scarlet tanager, red-headed and red-bellied woodpeckers, black-billed and yellow-billed cuckoos, broad-winged hawk, kingfisher, great blue heron, and great horned owl. The endangered sharp-shinned hawk (Accipiter striatus), veery (Catharus fuscescens), and red-shouldered hawk (Buteo lineatus) have been observed as nesting residents of the Thatcher Woods unit. |