This IBA consists of a series of sites along the west shore of Green Bay, including the County Line Swamp south of Peshtigo, owned by Marinette and Oconto County Forests; nine units of the Green Bay West Shores State Wildlife Area; a DOT mitigation site; a State Natural Area; a Brown County park; and a City of Green Bay park. These areas contain significant tracts of both open and forested wetlands, including emergent marsh, sedge meadow, shrub swamp, and lowland hardwood forest. The hardwood swamp found at County Line Swamp is particularly large, dominated by black ash. There also are some patches of upland hardwood forest.
This is a significant wetland site for both migrating and breeding birds. High priority breeders include osprey, red-shouldered hawk, American black duck, American bittern, American woodcock, black-billed cuckoo, sedge wren, and golden-winged warbler. Waterfowl, shorebirds, and landbirds use the site extensively during migration. Waterbirds from breeding colonies elsewhere in Green Bay, including Caspian, common, and Forster’s terns and American white pelicans, use this site for foraging.