Breeding Biology of Wood Ducks Using Natural Cavities in Southern Illinois

Abstract

Information on breeding biology of wood ducks (Aix sponsa) acquired largely through studies of artificial nest boxes may not represent natural cavities where most wood ducks are produced. We studied nesting biology of wood ducks using natural cavities in southern Illinois during springs 1993-95. Forty-four radiomarked females were tracked to nest sites, but these represented only 56% of resident females alive during the breeding season. Most (82%) nests were in upland forest beyond the Mississippi River floodplain where birds were captured. Six of 23 (26%) nests were parasitized, which is a rate higher than previously reported for natural cavities (12%), but is less than in nest boxes (40%). Nest success (64%) was higher than reported elsewhere in natural cavities (40%), but below that in nest boxes (66-75%). Success rates did not differ between floodplain (80%) and upland (59%) nests (P = 0.205). Duckling survival to fledging was high (42%), despite lengthy (x = 1.4-3.2 km) movements over mostly upland terrain. In our study, 2.9 ducklings fledged per nest attempt, compared to 3.8 ducklings per nest attempt from boxes in Tennessee. Low nesting effort and high rates of nest parasitism could have resulted from suboptimal habitat conditions in 1994 and 1995. In 1994, dry conditions during prenesting, followed by sudden flooding during egg laying and early incubation, were associated with a shorter nesting season (91 vs. 132 days), smaller proportions of nesting birds (42 vs. 57%), more nest parasitism (43 vs. 18%), and lower survival (55 vs. 81%) compared to 1995, when conditions were dry, but water levels were stable. Upland forests may be important sources of wood duck production in other areas where extensive loss and fragmentation of floodplain forest have occurred.