This IBA encompasses numerous state, federal, and NGO properties including Audubon Goose Pond State Natural Area, Erstad Prairie, and Ostego Marsh (Madison Audubon Society); Grassy Lake State Wildlife Area/ State Natural Area, Mud Lake State Wildlife Area, and units within Empire Prairies State Natural Area (WDNR); and Schoenberg Marsh Waterfowl Production Area and nine other federal WPAs (USFWS, NRCS). Wetlands are prominent at this site, with sedge meadow, wet prairie, shallow and deep-water marshes all present. There also are areas of oak savanna, oak forest, shrub carr, restored prairie, native prairie remnants, idle grassland, cropland, and flowages.
This site is significant to both wetland and grassland breeding birds, including red-necked grebe, mallard, least and American bitterns, Wilson’s snipe, American woodcock, black tern, willow flycatcher, dickcissel, grasshopper sparrow, bobolink, Eastern meadowlark, and yellow-headed blackbird. Great egrets congregate here in summer and early fall, and migrating waterfowl frequent the wetlands in both spring and fall. Migrating shorebirds can be abundant in years when fluctuating water levels expose mudflats. Short-eared owls are regular in winter.