Natural-Cavity Use by Nesting Wood Ducks in Illinois

Abstract

Information on the availability and use of natural cavities by nesting wood ducks (Aix sponsa) in floodplain forests of the Midwest is lacking. We studied the abundance of suitable cavities and use by nesting wood ducks at Sanganois Conservation Area in westeentral Illinois, 1994-95. Ninety-seven 0.5-ha plots randomly located in palustrine forested wetland contained 103 (86 climbable) suitable cavities (2.12 ± 0.23 cavities/ ha; x ± SE). Silver maple (Acer saccharinum) accounted for 74.3% of the suitable cavities, followed by eastern cottonwood (Populus deltoides; 8.2%), willow (Salix spp.; 8.0%), green ash (Fraxinus pennsylvanica; 6.7%), and American sycamore (Platanus occidentalis; 1.9%). The minimum number of wood duck nests per hectare of palustrine forested wetland was 0.21 in 1994 and 0.12 in 1995. Among natural cavities considered suitable for nesting, wood ducks used cavities with small entrances and cavities excavated by pileated woodpeckers (Dry ocopus pileatus) in greater proportion than available. Apparent success for the combined 1994-95 sample of nests was 21.4% (3 of 14 nests). Raccoons (Procyon lotor) were the primary predator of wood duck nests and destroyed 6 of 14 nests with known fates. Predation rather than nest-site availability limited wood duck production from natural cavities. Tree mortality (42.7% of 75 monitored trees containing potentially suitable nest cavities) resulting from flooding in 1993 and 1995 may limit cavity availability and wood duck production for several decades.