The IBA consists of three separate areas: 1) Cowan Lake State Park, owned and operated by ODNR Division of Parks and Recreation, consists of extensive open water areas, deciduous forest, and emergent wetland, along with mudflat areas during periods oflake draw-down; 2) Dean A. Culberson State Nature Preserve, owned and operated by ODNR’s Division of Natural Areas and Preserves, consists of approximately 200 acres of forested wetland and Illinoisan till plain swamp forest, probably the largest and best example of this very rare habitat type; 3) Cowan Creek Road, which runs along the northern edge of Cowan Creek from just west of the Cowan Lake spillway to the intersection of Clarksville Road, features riparian forested area roughly 500 feet on either side of Cowan Creek for its full extent.
Cowan Lake regularly supports significant concentrations of migrating waterfowl, and several rarities have been identified over the years, including Surf Scoter, White-winged Scoter, Red-throated Loon, White-fronted Goose, and Long-tailed Duck. During the later fall season, the lake is drawn down and substantial mudflat areas develop at the eastern end of the park. This habitat has become a regular migration stopover spot for Sandhill Cranes. This species has been reported frequently in the last fifteen years, with numbers ranging from a few individuals to approximately 240. Some years this species is observed for only a few hours, whereas in others the cranes will stay for several days to a few weeks. The spillway and beach areas have also occasionally attracted rare migrants, including Sanderling, Ruddy Turnstone, White-rumped Sandpiper, and Wilson’s Phalarope. Several high-priority conservation species have been recorded as nesting in the upland forests surrounding the lake itself. These include Red-shouldered Hawk, Cerulean Warbler, Prothonotary Warbler, Yellow-billed Cuckoo, and Red-headed Woodpecker.
Dean A. Culberson State Nature Preserve is composed mainly of the very rare Illinoisan till-plain swamp forest habitat. In 1991, a Great Blue Heron rookery was discovered in the center of the forest, with a nest count of 30 to 35. During 1993 two singing Veeries were present during the nesting season. Very few records of nesting exist for this species in southwest Ohio (none in Clinton County). Extremely large concentrations of nesting Wood Thrushes were also present during the early 1990s, probably at least in part due to the high density of spice?bush ‘Lindera benzoin’ throughout this forested wetland. During fall and winter months, large flocks of Red-headed Woodpeckers have been observed (30+ individuals), possibly attracted to a large number of mature pin oaks dominating the forest overstory. Additionally, anecdotal evidence from a few spring dates in the early 1990s suggests that this preserve may provide significant habitat for migrating warblers as very large numbers of birds and a high diversity of species were observed. These observations were made when there was about .5 foot of standing water throughout the forest (typical winter/spring conditions for this ecosystem), and the density of mosquitoes was extremely high.
The mature riparian forest surrounding Cowan Creek has been found to contain substantial evidence of nesting of high-priority species (Red-shouldered Hawk, Cerulean Warbler, Yellow-billed Cuckoo), as well as several other species relatively rare in southwest Ohio (Black-and-white Warbler, Hooded Warbler, and Northern Parula).