Richard M. Kaminski

Waste Rice for Waterfowl in the Mississippi Alluvial Valley

Abstract 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.

Moist-soil seed abundance in managed wetlands in the Mississippi Alluvial Valley

Abstract 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.

WATERBIRD FOODS IN WINTER-MANAGED RICEFIELDS IN MISSISSIPPI

Abstract Ricefields are important foraging habitats for waterfowl and other waterbirds in primary North American wintering regions. We conducted a large-scale experiment to test effects of post-harvest ricefield treatment, winter water management, and temporal factors on availabilities of rice, moist-soil plant seeds, aquatic invertebrates, and green forage in the Mississippi Alluvial Valley (MAV), Mississippi, USA, fall–winter 1995–1997. Our results revealed that a large decrease in rice grain occurred between harvest and early winter (79–99%), which, if generally true throughout the MAV, would have critical implications on foraging carrying capacity of ricefields for migrating and wintering waterbirds. During the remainder of winter, food resources generally were similar among treatment combinations. An exception was biomass of aquatic invertebrates, which demonstrated potential to increase by late winter in ricefields that remained flooded. We offer revised calculations of foraging carrying capacity for waterfowl in MAV ricefields and recommend continuing research and management designed to increase availability of residual rice and aquatic invertebrates in winter.

AFFORESTATION OF BOTTOMLAND HARDWOODS IN THE LOWER MISSISSIPPI ALLUVIAL VALLEY: STATUS AND TRENDS

The Lower Mississippi Alluvial Valley (LMAV) originally supported at least 10 million ha of bottomland hardwood (BLH) forests. Many of these forests were wetlands and provided a diversity of values that were not recognized fully until at least one-half of the original forested area had been converted primarily to row-crop agriculture. Efforts to restore these forests have expanded in proportion to growing recognition of their unique values. This paper provides a summary resulting from a survey of BLH afforestation by all agencies and private entities in Arkansas, Louisiana, and Mississippi, the three states in the LMAV with the most restoration activity and, more specifically, by the U.S. Fish and Wildlife Service, the U.S.D.A. Natural Resources Conservation Service, and state wildlife management agencies, the three entities responsible for approximately 95% of the afforestation in this region. There is a promising trend in the annual increase of BLH afforestation across the LMAV. Approximately 71,000 ha have been planted with BLH species through 1998; however, this represents <1% of the BLH forests that have been lost, and afforestation does not ensure restoration of all ecological functions. No clear choice between planting stocks (bareroot seedlings or direct seeding) or among planting seasons (Fall, Winter, Spring, or Summer) is prevalent among those involved in BLH afforestation. Much of the early afforestation used oaks (Quercus spp.) to accelerate replacement of mast-bearing species. Recently, mixtures of species have been incorporated into afforestation regimes. More light-seeded species and a more diverse component of oak species have been planted to mimic a more natural regeneration process. Successful widescale afforestation is a critical link in restoration of functional BLH ecosystems in this region.

Avian Foods, Foraging and Habitat Conservation in World Rice Fields

Abstract. Worldwide, rice (Oryza sativa) agriculture typically involves seasonal flooding and soil tillage, which provides a variety of microhabitats and potential food for birds. Water management in rice fields creates conditions ranging from saturated mud flats to shallow (<30 cm) water, thereby attracting different guilds of birds. Grain not collected during harvest (i.e. waste rice) is typically the most abundant potential food of birds in rice fields, with estimates of seed mass from North America ranging from 66–672 kg/ha. Although initially abundant after harvest, waste rice availability can be temporally limited. Few abundance estimates for other foods, such as vertebrate prey or forage vegetation, exist for rice fields. Outside North America, Europe and Japan, little is known about abundance and importance of any avian food in rice fields. Currently, flooding rice fields after harvest is the best known management practice to attract and benefit birds. Studies from North America indicate specific agricultural practices (e.g. burning stubble) may increase use and improve access to food resources. Evaluating and implementing management practices that are ecologically sustainable, increase food for birds and are agronomically beneficial should be global priorities to integrate rice production and avian conservation. Finally, land area devoted to rice agriculture appears to be stable in the USA, declining in China, and largely unquantified in many regions. Monitoring trends in riceland area may provide information to guide avian conservation planning in rice-agriculture ecosystems.

Weather-Related Indices of Autumn–Winter Dabbling Duck Abundance in Middle North America

Abstract Research on effects of key weather stimuli influencing waterfowl migration during autumn and winter is limited. We investigated relationships between changes in relative abundances of mallard (Anas platyrhynchos) and other dabbling ducks (Anas spp.) and weather variables at midlatitude locations in North America. We used waterfowl survey data from Missouri Conservation Areas and temperature and snow cover data from the Historical Climatology Network to evaluate competing models to explain changes in relative abundance of ducks in Missouri, USA, during autumn–winter, 1995–2005. We found that a cumulative weather severity index model (CumulativeWSI; calculated as mean daily temp − degrees C + no. of consecutive days with mean temp ≤0° C + snow depth + no. of consecutive days with snow cover) had the greatest weight of evidence in explaining changes in relative abundance of ducks. We concluded the CumulativeWSI reflected current and cumulative effects of ambient temperatures on energy expenditure by ducks, and snow cover and wetland icing, on food availability for ducks. The CumulativeWSI may be useful in determining potential changes in autumn–winter distributions of North American waterfowl given different climate change projections and associated changes in habitat conservation needs. Future investigations should address interactions between CumulativeWSI and landscape habitat quality, regional waterfowl populations, hunter harvest, and other anthropogenic influences to increase understanding of waterfowl migration during autumn–winter.

Agricultural Seed Biomass for Migrating and Wintering Waterfowl in the Southeastern United States

Abstract Waterfowl frequently acquire high-energy agricultural seeds in harvested and unharvested croplands during migration and winter. Estimates of agricultural seed biomass in harvested and unharvested corn, soybean, and grain sorghum fields do not exist or are outdated for the southeastern United States. Therefore, we estimated seed biomass in 105 harvested and 59 unharvested corn, soybean, and grain sorghum fields across 4 climate regions in Tennessee, USA, from September through January 2006 and 2007. We also used estimates of seed biomass to calculate duck-energy days (DEDs) in December and January when migratory waterfowl abundance peaks in the southeastern United States. Mean biomass of corn, soybean, and grain sorghum seed in harvested fields declined 239 kg/ha to 39 kg/ha, 118 kg/ha to 26 kg/ha, and 392 kg/ha to 19 kg/ha, respectively, from postharvest to January. Continuous monthly rates of decline were 64% for corn, 84% for soybean, and 74% for grain sorghum. Agricultural seed biomass in harvested corn and grain sorghum fields dropped below the waterfowl giving-up density (i.e., 50 kg/ha) in 3 months; soybean dropped below this threshold 1 month postharvest. Mean DEDs/ha in harvested corn, soybean, and grain sorghum fields were low (274, 90, and 27, respectively) in January, and DEDs were zero in >85% of fields. In unharvested corn, soybean, and grain sorghum fields, mean DEDs/ha in January were high (69,000, 18,000, and 26,000, respectively), and continuous rates of decline (3%, 7%, and 18%, respectively) were much lower than for harvested crops. Waterfowl biologists in the Southeast should use our estimates of agricultural seed biomass in DED calculations. We also recommend that biologists provide unharvested grain fields and natural wetlands for migrating and wintering waterfowl because seed resources are low in harvested agricultural fields.

Dabbling duck-habitat associations during spring in Delta Marsh, Manitoba

We conducted helicopter surveys of dabbling ducks (Anatini) in randomly selected legal quarter sections (64.8 ha) in the Delta Marsh, Manitoba, between April and June 1976-78. Our objective was to census indicated pairs of five species (Anas acuta, A. clypeata, A. discors, A. platyrhynchos, A. strepera) to test for associations of species pair densities and species richness with floristic and physiognomic character- istics of surveyed areas. Water levels in Delta Marsh varied markedly among years with 1976, 1977, and 1978 representing high, low, and intermediate levels, respectively. Densities of most species increased dra- matically in 1977, a year of widespread drought. We suggest this resulted from influxes of dabblers displaced from drought-stricken habitats. Tests for dabbler-habitat correlations with stepwise multiple regression revealed several patterns. Pair densities of most species and species richness were positively correlated with the proportional cover of shallow marsh habitat within survey quarters in 1976, but negatively associated with the cover of forest in 1977. Only mallard, northern pintail, and species richness were positively asso- ciated with an index of emergent vegetation-water interspersion in all 3 years. We provide explanations for consistent habitat correlations and offer considerations for marsh management and future research.

Estimation and Correction of Visibility Bias in Aerial Surveys of Wintering Ducks

Abstract Incomplete detection of all individuals leading to negative bias in abundance estimates is a pervasive source of error in aerial surveys of wildlife, and correcting that bias is a critical step in improving surveys. We conducted experiments using duck decoys as surrogates for live ducks to estimate bias associated with surveys of wintering ducks in Mississippi, USA. We found detection of decoy groups was related to wetland cover type (open vs. forested), group size (1–100 decoys), and interaction of these variables. Observers who detected decoy groups reported counts that averaged 78% of the decoys actually present, and this counting bias was not influenced by either covariate cited above. We integrated this sightability model into estimation procedures for our sample surveys with weight adjustments derived from probabilities of group detection (estimated by logistic regression) and count bias. To estimate variances of abundance estimates, we used bootstrap resampling of transects included in aerial surveys and data from the bias-correction experiment. When we implemented bias correction procedures on data from a field survey conducted in January 2004, we found bias-corrected estimates of abundance increased 36–42%, and associated standard errors increased 38–55%, depending on species or group estimated. We deemed our method successful for integrating correction of visibility bias in an existing sample survey design for wintering ducks in Mississippi, and we believe this procedure could be implemented in a variety of sampling problems for other locations and species.

Estimation and correction of seed recovery bias from moist-soil cores†

ABSTRACT Scientists estimate seed abundances to calculate seasonal carrying capacities and assess wetland management actions for waterfowl and other wildlife using soil core samples. We evaluated recovery of known quantities of moist-soil seeds from whole and subsampled experimental core samples containing 12 seed taxa representing small, medium, and large size classes. We recovered 86.3% (SE = 1.8) of all seeds added to experimental cores; 8.3% (SE = 1.2) of seeds were destroyed during the sieving process and 5.4% (SE = 1.2) were not recovered by observers. Recovery rates varied by seed size, but not seed quantity or disproportionate ratios of seed-size classes. Overall seed recovery rates were similar between subsampled ( = 81.2%, SE = 3.6) and whole—processed core samples ( = 86.3%, SE = 1.8). We used recovery rates to generate size-specific, taxon-specific, and constant correction factors and applied each to actual core sample data. Size-specific correction factors increased seed mass estimates in the Mississippi Alluvial Valley ( = 10.1%, SE = 0.32), upper Midwest ( = 21.2%, SE = 0.61), and both regions combined ( = 15.7%, SE = 0.51) differently, as seed composition in core samples varied regionally. We suggest scientists consider using size-specific correction factors to account for seed recovery bias in core samples because these factors may be applied to a variety of taxa and produced similar mass estimates as taxon-specific correction factors. However, if data from core samples are unavailable at the resolution of seed size classes, we suggest increasing seed mass estimates by 16% to account for seed recovery bias.