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Published: 2012

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Red oaks (Quercus spp.; Section Erythrobalanus) produce acorns which are valuable forage for wildlife especially mallards (Anas platyrhynchos) and wood ducks (Aix sponsa). Scientists have limited information on amount, timing, and persistence of these acorns in the Mississippi Alluvial Valley (MAV). Conservation planners rely on precise estimates of acorns and other forage to estimate habitat needed by waterfowl in the MAV and other regions. My study provided premiere landscape-scale, multi-year estimates of red oak acorn yield and on-ground abundance in the MAV. Mean yield of acorns was 534 kg(dry)/ha (42.3 acorns/ m2) across all sites, years (falls-winters 2009-2012), and oak species. Yield varied more within years (CV = 11 - 29%) than when data were combined across years (CV = 11%). Yield was not synchronized in any year among MAV sites. However, yield usually was synchronized among species within sites suggesting local factors influenced acorn yield more than landscape-scale factors. Among sites and years, acorn abundance generally was greatest in January (sample mean = 371 kg/ha) and least in November (198 kg/ha). Acorns persisted to February only in years of above-average yield. Except for Nuttall oak (Quercus texana), acorn persistence generally was stable regardless of yield from parent trees. Nuttall oak acorn persistence increased with yield perhaps revealing an evolutionary pressure that encourages masting. Red oak acorn abundance was linearly related to percentage of red oaks in the overstory, but this relationship differed in years of above- and below-average yield. Currently, conservation planners use 166 kg/ha as a forage estimate of red oak acorns, moist-soil seeds, and aquatic macro-invertebrates in bottomland hardwood forests with 100% red oak canopy. I sampled at 5 sites throughout the MAV over 3 years; therefore, I recommend conservation planners consider adopting my predicted estimate of 247 kg of acorns/ha of forest land with 100% red oak canopy. Because acorns persist through most winters and generally reach peak abundance in January, often concomitant with peak abundance of mallards and other ducks in the MAV, biologists and conservation planners may have undervalued the potential of bottomland hardwood forests to support ducks in mid-late winter.