Lake Chautauqua impounds about 3,500 acres of water. Another 800 acres of water and timbered bottomland are located outside of the impounded area. The remaining acreage is composed of upland and timber. Peak fall waterfowl populations average nearly a quarter of a million birds. The average peak concentration during early winter normally exceeds 100 thousand ducks and up to 40 thousand geese.
Mallards comprise the bulk of the duck population during migration.
Summer records for some shorebirds, flycatchers and swallows actually represent early fall migrants. The following birdlist contains 254 species representing observations since 1938. Another 20 birds, listed under Accidentals, have been reported but are not normally expected to be present. The list is in accordance with the current A.O.U. checklist. Birds of Chautauqua National Wildlife Refuge, Illinois.