Find Nature In Illinois

Additional Wildlife of Illinois

To flesh out your understanding of the region’s natural history, here is a breakdown of the specific taxa you can expect to encounter in the Prairie State.

Birds (Avifauna) The ghost of the prairie is the Greater Prairie-Chicken, a bird that was once abundant but now exists only in small, intensively managed populations in places like Jasper County. Their spring mating ritual, where males inflate orange air sacs and “boom” to attract females, is one of the rarest spectacles in the state. Along the Mississippi River, Illinois hosts one of the largest wintering populations of Bald Eagles in the lower 48 states; the churning water below the locks and dams keeps the river ice-free, allowing the eagles to fish throughout the winter.

Mammals The American Bison has returned to Illinois, not as free-roaming herds, but as a keystone ecological tool at the Nachusa Grasslands and Midewin. Their grazing patterns are essential for maintaining the diversity of the prairie flora. The Nine-banded Armadillo is a recent arrival, steadily expanding its range northward into southern Illinois as winters become milder. The Bobcat, once threatened, has rebounded significantly in the wooded valleys of the Shawnee National Forest and is now a top predator in that system.

Insects Illinois plays a critical role in the conservation of the Hine’s Emerald Dragonfly, a federally endangered species. It relies on the rare dolomite prairie wetlands found in the Des Plaines River valley, where groundwater seeps through the limestone bedrock. The state insect is the Monarch Butterfly, and despite the heavy agriculture, there is a massive push to plant milkweed in roadside corridors to support their migration to Mexico. The Rusty Patched Bumble Bee, another federally endangered species, has been found clinging to survival in the urban and suburban gardens of northern Illinois.

Plants Big Bluestem is the state grass, iconic for its “turkey foot” seed head and root systems that can extend ten feet deep, anchoring the soil against erosion. In the sandy deposits along the Illinois River, you can find the Eastern Prickly Pear Cactus, surviving in the “sand prairies” that mimic desert conditions. The White Oak is the state tree and a master of the savanna ecosystem, its fire-resistant bark allowing it to survive the periodic burns that kept the prairies open.

Fungi The Morel (specifically Morchella esculenta) is culturally significant in Illinois, driving a massive annual harvest in the river bottoms during late April. The state is also home to the Jack-o’-lantern Mushroom, which grows in large orange clusters at the base of trees and is bioluminescent, though it is often mistaken for the edible chanterelle with painful consequences. In the oak woodlands, the Hen of the Woods (Grifola frondosa) is a common autumn find, often growing to massive sizes at the base of old oaks.

Illinois Biodiversity Profile

Illinois is often perceived as a monolith of flat agricultural land, but biologically, it is a complex tension zone where the eastern deciduous forests met the vast western tallgrass prairies. The defining ecological feature of the state was historically the Grand Prairie, a sea of grasses like Big Bluestem and Indian Grass that grew so tall they could hide a person on horseback. While less than 0.1% of this original prairie remains, restoration efforts at places like the Midewin National Tallgrass Prairie are bringing back the bison and the complex soil ecology that defined the region for millennia. These deep, carbon-rich soils (Mollisols) are the direct result of thousands of years of prairie root systems dying and regenerating.

To the northwest, the state breaks its flat reputation in the Driftless Area. This region in Jo Daviess County was missed by the glaciers that smoothed out the rest of the state. Consequently, it is a rugged landscape of steep ridges, deep river valleys, and limestone bluffs. This topography serves as a glacial refugium, hosting “relict” species of plants and animals that are typically found much further north, surviving here in the cool, shaded microclimates of the north-facing slopes.

At the southern tip of the state, the ecology shifts dramatically in the Shawnee Hills and Coastal Plain. Here, the influence of the glaciers ends, and the landscape begins to resemble the Ozarks and the Mississippi Delta. The Cache River Wetlands are a biological standout—a true northern cypress-tupelo swamp. In these dark, slow-moving waters, massive bald cypress trees, some over 1,000 years old, create a bayou ecosystem that supports species more commonly associated with Louisiana than the Midwest, such as the bird-voiced treefrog and the cottonmouth snake.

Defining the western border is the Mississippi River, a global migration superhighway. The river’s backwaters and islands provide critical staging areas for waterfowl and eagles. The “Big Rivers” region, where the Illinois and Missouri rivers join the Mississippi, creates a funnel effect for wildlife, concentrating biodiversity in the floodplains and bluffs that line the waterways.