Summary

Description

We studied diurnal activity and habitat use patterns of waterfowl on Swan Lake in Calhoun County, IL during fall and spring migrations 199293. Swan Lake, a 1,255 ha backwater lake near the confluence of the Illinois and Mississippi Rivers Pool 26, was selected as a site for a Habitat Rehabilitation and Enhancement Project HREP under the Upper Mississippi River system Environmental Management Program. This study was conducted to obtain baseline data on waterfowl use of Swan Lake for comparison with results of postproject evaluations. Swan Lake was used primarily as a resting area during fall and spring migration; waterfowl populations peaked in early November, and in late February to midMarch. Dabbling ducks included mostly mallards Anas platyrhyncos , while lesser scaup Aythya affinis and ringnecked ducks Aythya collaris comprised the majority of diving ducks. Geese consisted mainly of snow geese Chen caerulescens. Divers were observed mostly in open water habitat during fall 98 and spring 70. Moist soil habitats received little use by waterfowl during fall, but 2154 of geese, dabblers and divers were observed there in spring. Dabbling ducks made the greatest use during fall 44 of nearshore habitats that were exposed at low lake levels in summer. Overall, resting was the predominant activity of waterfowl during fall and spring migration, but feeding activity increased in habitats where aquatic macroinvertebrates and macrophytes were more abundant. Less than 10 of ducks were observed feeding in open water habitats, but 6470 were observed feeding in submerged aquatic and moist soil habitats during fall. Very little feeding was observed among diving ducks in spring, but 28 of dabblers were observed feeding in moist soil and nearshore emergent habitats. If installation of levees and water control structures, combined with implementation of effective water level management, enhances aquatic plant and invertebrate communities, habitat conditions will improve for waterfowl. Waterfowl populations should respond numerically increased usedays andor functionally increased feeding and residence times to increased availability of food and cover.