Abstracts

P.1-13: Use of next boxes by wood ducks and hooded mergansers at Noxubee and Yazoo National Wildlife Refuges in Mississippi

Daniel A. Davis, Department of Forestry, Mississippi State University, Box 9690, Mississippi State, MS 39762, USA
J. Brian Davis, Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Box 9690, Mississippi State, MS 39762, USA
Richard M. Kaminski, James C. Kennedy Waterfowl and Wetlands Conservation Center, Clemson University, Box 596, Georgetown, SC 29442
Scott E. Stephens, Ducks Unlimited Canada, PO Box 1160 1 Mallard Bay at Hwy. 220 Stonewall, MB R0C 2Z0.

Presented by J. Brian Davis - Email: brian.davis@msstate.edu

Use of artificial nesting structures (hereafter, nest boxes) for wood ducks (Aix sponsa) have a storied history in North America. Nest boxes are often used by other species of cavity-nesting birds, including hooded mergansers (Lophodytes cucullatus). Previous experiments using conventional-sized and small experimental nest boxes (approximately half the size of conventional boxes) at two sites in Mississippi documented variable use and wood duck duckling survival relative to box size, study area, time of breeding season, and other factors. Herein, we report preliminary results for shared use of next boxes by wood ducks and hooded mergansers at Noxubee and Yazoo National Wildlife Refuges, monitoring them at both areas from 1994-1997. At Noxubee we found 460 unique nests in 122 nest boxes, and 356 (77%) nests were successful. Of the successful nests, 87 (~25%) contained eggs of both duck species. At Yazoo, we found 423 nests in 77 nest boxes, and 259 nests (61%) were successful. Of the successful nests, 25 nests (~10%) contained eggs of both species. Pooled collectively across both box types, refuges, and years, the proportion of non-host eggs in a clutch being incubated by the host ranged from ca. 15-25% By modeling potential costs of being parasitized interspecifically with clutches of 12 and 14 host wood ducks eggs, and no hooded merganser eggs, 9.4 and 10.8 wood duck eggs hatched, respectively in those nests. When 1-5 hooded merganser eggs were present in those wood duck nests, hatching of wood duck eggs only declined by 1.3 and 1.5 eggs, respectively. When hooded mergansers were host and had a clutch of 15 eggs, and no wood duck eggs present, mergansers hatched 14.6 eggs. However, when 1-5 wood duck eggs were present in these nests, 5.3 and 10.3 fewer merganser eggs hatched across their range. Clearly, further work is needed to investigate causes of these potential declines, particularly the consequences to hooded mergansers upon being parasitized by wood ducks. These results are preliminary; however, the number of shared nests for these species in this four-year study represents some of the greatest reported in North America.