Flooded rice fields are important foraging habitats for waterfowl in the lower Mississippi Alluvial Valley (MAV). Waste rice previously was abundant in late autumn (140–492 kg/ha), but early planting and harvest dates in recent years may have increased losses of waste rice during autumn before waterfowl arrive. Research in Mississippi rice fields revealed waste-rice abundance decreased 79–99% during autumns 1995–1996 (Manley et al. 2004). To determine if this trend existed throughout the MAV, we used multistage sampling (MSS) to estimate waste-rice abundance during September–December 2000–2002. Averaged over years, mean abundance of waste rice decreased 71% between harvest (x̄ = 271.0 kg/ha, CV = 13% n = 3 years) and late autumn (x̄ = 78.4 kg/ha, CV = 15% n = 3). Among 15 models formulated to explain variation in rice abundance among fields and across years, the best model indicated abundance of waste rice in late autumn differed between harvester types (i.e., conventional > stripper header) and was positively related to initial waste-rice abundance after harvest. Because abundance of waste rice in late autumn was less than previous estimates in all 3 years, we concluded that waterfowl conservationists have overestimated carrying capacity of rice fields for wintering waterfowl by 52–83% and recommend 325 duck-use days/ha (DUDs) as a revised estimate. We suggest monitoring advances in rice harvest dates to determine when new surveys are warranted and recommend increased management of moist-soil wetlands to compensate for decreased rice abundance.
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Vol. 70 • No. 1