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.

Managed moist‐soil units support early succession herbaceous vegetation that produces seeds, tubers, and other plant parts used by waterfowl in the Mississippi Alluvial Valley (MAV), USA. We conducted a stratified multi‐stage sample survey on state and federal lands in the MAV of Arkansas, Louisiana, Mississippi, and Missouri during autumns 2002–2004 to generate a contemporary estimate of combined dry mass of seeds and tubers (herein seed abundance) in managed moist‐soil units for use by the Lower Mississippi Valley Joint Venture (LMVJV) of the North American Waterfowl Management Plan. We also examined variation in mean seed abundance among moist‐soil units in 2003 and 2004 in relation to management intensity (active or passive), soil pH and nutrient levels, proportional occurrence of plant life‐forms (e.g., grass, flatsedge, and forb; vine; woody plants), and unit area. Estimates of mean seed abundance were similar in 2002 (x̄ = 537.1 kg/ha, SE = 100.1) and 2004 (x̄ = 555.2 kg/ha, SE = 105.2) but 35–40% less in 2003 (x̄ = 396.8 kg/ha, SE = 116.1). Averaged over years, seed abundance was 496.3 kg/ha (SE = 62.0; CV = 12.5%). Multiple regression analysis indicated seed abundance varied among moist‐soil units inversely with proportional occurrence of woody vegetation and unit area and was greater in actively than passively managed units (R2adj = 0.37). Species of early succession grasses occurred more frequently in actively than passively managed units (P ≤ 0.09), whereas mid‐ and late‐succession plants occurred more often in passively managed units (P ≤ 0.02). We recommend the LMVJV consider 556 kg/ha as a measure of seed abundance for use in estimating carrying capacity in managed moist‐soil units on public lands in the MAV. We recommend active management of moist‐soil units to achieve maximum potential seed production and further research to determine recovery rates of seeds of various sizes from core samples and the relationship between seed abundance and unit area. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):707–714; 2008)

No abstract

No abstract

No abstract