SREL Reprint #2576




Relating climatological patterns to wetland conditions and wood duck production in the Southeastern Atlantic Coastal Plain

Robert A. Kennamer

Savannah River Ecology Laboratory, P.O. Drawer E, Aiken, SC 29802

Abstract: Efforts to index annual population size and recruitment of the wood duck (Aix sponsa) on
a geographic scale sufficiently large to be useful in managing this species have met with mixed results. A general relationship between climatic factors and wood duck production has been the most economical and promising approach, particularly in the Southeast, though further refinement or understanding of factors mediating the relationship has been lacking. Development of climate-based models that predict wetland hydrologic conditions during the wood duck breeding season can be a useful step to index recruitment and may provide useful insights into population dynamics. In this study, I illustrate the concept's potential by developing a robust deterministic model of wetland water conditions on the 78,000-ha Savannah River Site (SRS) in west-central South Carolina over a 13-year period (1984-1996). During 6 years (1982-1987) when more than 90% of all hatched ducklings were marked before leaving nest boxes on the SRS, production of female ducklings was related positively to estimated female recruitment into the population the following year (combined breeding and nonbreeding yearling population segments; rS=0.90, P=0.015), indicating that duckling production was a reasonable proxy for recruitment. The return of females initially marked as ducklings suggested that deferred yearling breeding was highest in dry years that were preceded by wetter years, thereby contributing to lower productivity in such years. Annual wetland condition indices were related to 15 years of duckling production from SRS nest boxes. Productivity of wood ducks was positively associated with wetland hydrologic conditions. In wet years, an average of 9.8±0.7 (SE) ducklings was produced by each female in the breeding population, but only 8.6±0.5 (SE) ducklings/female were produced in dry years. Greater productivity in wet years was attributed in part to longer breeding seasons, which allowed more females in the population to produce second broods, and to reduced predation rates. Additional insights gained through application of the method are discussed.

Keywords: Aix sponsa, Carolina bay, climate, hydrologic condition, South Carolina, Southeastern
Atlantic Coastal Plain, wetland, wood duck

SREL Reprint #2576

Kennamer, R. A. 2001. Relating climatological patterns to wetland conditions and wood duck production in the southeastern Atlantic coastal plain. Wildlife Society Bulletin 29:1193-1205.

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