Waterbird habitat in the Saskatchewan River Delta (SRD) has been altered by numerous upstream and downstream anthropogenic developments. Wetland water-level management has been used in an attempt to mitigate these changes, but the effects on the local waterbird community are unknown. Using an experimental approach, I examined the effects of wetland water-level management on waterfowl and marsh birds in the SRD. In 2007, three wetland basins in the Summerberry Marsh Complex, Manitoba were partially drawn down and paired with three additional wetlands managed with high water levels. In 2008-09, I surveyed waterfowl within the study wetlands during different life stages using point counts and aerial surveys. Abundances of breeding marsh birds, including American Bitterns, Least Bitterns, Soras, Virginia Rails, Yellow Rails, American Coots, and Pied-billed Grebes were estimated using call-response surveys. Generalized linear and generalized linear mixed models were used to determine relationships between relative bird abundances and the physical characteristics, vegetation characteristics, and forage fish and invertebrate abundances within the wetlands. Dabbler species of waterfowl preferred the partial drawdown wetlands during nearly all life stages, except brooding. Diver species preferred the non-drawdown wetlands, but only during the spring-breeding and fall-staging periods. Invertebrate abundance affected wetland use by dabbler and diver species, particularly during the spring-breeding and brooding periods. Subsequently, wetlands with high forage fish abundances were avoided. In the fall, dabbler densities on the partial drawdown wetlands increased from an average of 0.4 birds per hectare to 1.5 birds per hectare. This influx was likely due to the accessibility and availability of submerged aquatic vegetation. The partial water-level drawdowns did not benefit any species of marsh birds examined. American Bitterns, American Coots, and Pied-billed Grebes chose the deeper, non-drawdown wetlands, due to high abundances of forage fish. Vegetation interspersion, particularly that offered by Schoenoplectus, was preferred by these species. Soras and Virginia Rails were not affected by water depth or vegetation characteristics, but were positively correlated to invertebrate abundances. Subsequently, the Sora avoided wetlands with high forage fish abundance. The conditions created by the partial water-level drawdowns did not meet the requirements of all species present in the SRD. Therefore, future wetland management should focus on providing a wide range of water depths within wetland complexes to accommodate the requirements of different avian species.

Thesis (M.S. - Renewable Natural Resources)--University of Arizona, 1982. / Includes bibliographical references (leaves 72-78).

Thesis (Ph. D.)--Oregon State University, 1990. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--University of Wisconsin -- La Crosse, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 188-192).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 62-65). Also available on the World Wide Web.

Strategies animals use to find and consume food in the face of conflicting forces such as competition and predation are central questions in the fields of ecological theory and management. Whereas theoretical models abound, proper empirical tests of these theories are less abundant. In studying the relationship between food abundance, predation risk, and competition there exists an array of confounding factors, which need to be accounted for by manipulating some aspect of the system. I used a guild of spring migratory ducks as a model system and manipulated food abundance in areas differing in presumed risk to assess the relative effects of food abundance, predation risk, competition, and life history characteristics on foraging strategies used by ducks. Using a randomized block design, I established a pair of 0.4 ha plots (block) in emergent, open water, and forested wetlands in the Wabash River Floodplain in eastern Illinois. I randomly selected one plot within each block to supplement with 2000 kg/ha of corn (Zea mays), creating an area of very high duck food abundance next to a control area with no added food. I conducted instantaneous focal animal samples and used video recorders to estimate the proportion of time mallard (Anas platyrhynchos), blue-winged teal (Anas discors), wood duck (Aix sponsa), ring-necked duck (Aythya collaris), and lesser scaup (Aythya affinis) devoted to feeding, identify the specific behaviors used, and estimate feeding stint lengths and frequencies. I used these metrics as an index of risk that ducks were willing to engage in for a known food reward. I predicted that species with a faster life history strategy, factors that increase perceived predation risk (cover, water depth, group size), and increase energetic demand (due to nesting or temperature), would elicit more risk-taking behaviors in ducks. This would be realized by an increase in the proportion of time spent feeding, longer feeding durations, and deeper feeding behaviors in treatment plots compared with control plots. Consistent with my life history prediction, species with a faster life history strategy were willing to engage in more risky behavior (feeding more) for a greater food reward (food treatment). Mallards, lesser scaup, and wood ducks exhibited risk-taking behavior consistent with perceived predation risk. Mallards devoted more time to feeding and used longer feeding stints when in areas with less cover. Alternatively, lesser scaup devoted more time to feeding when in areas of more cover. Wood ducks devoted more time to feeding in treatment plots, when in shallow areas, and larger flocks. When blue-winged teal fed on the surface (eyes above water), they devoted more overall time to feeding indicating that surface feeding is less risky than deeper feeding. Wood ducks and lesser scaup exhibited behavior consistent with an increase in energetic demand as observed by an increase in the proportion of time devoted to feeding later in the spring. I also examined how food abundance influenced aspects of ducks' foraging niches. I found that dabbling ducks used a greater variety of behaviors (behavior niche breadth) when in treatment plots compared to control plots and also shifted to slightly deeper feeding behaviors in treatment plots. This greater breadth when food was more abundant was due to individuals of the same species diverging from one another, rather than each individual using a broader array of behaviors. Overall, I found substantial variability among and within species in how they manage risk while foraging, although this was partially explained by life history theory, and what types of conditions they perceive as risky. I document the importance of taking the state of the forager (life history, perceived risk, energetic demand) into account when examining patterns of risk-taking.

No description available.

Red oak (Quercus spp.) acorns provide food for wildlife and are propagules for regeneration of these trees. Annual yield of acorns varies temporally and site-specifically. I examined acorn yield in relation to hydrology and soils of hardwood bottomlands at five sites in the Mississippi Alluvial Valley and a site in the Mississippi Interior Flatwoods Region during fall-winter 2012-2013. Acorn yield varied among sites (mean = 44.9 acorns/m2; SE = 6.7; CV = 14.9%). Duration of flooding during the growing season differed among sites which influenced soil characteristics. Acorn yield varied inversely with number of days sites were inundated during the growing season (R2 = 0.6725; P = 0.0456; n = 6) during 2012-2013. Managers should consider alleviating growing season flooding of red oaks, which may increase acorn yield and sustain red oaks and other bottomland hardwoods.

Flood-control reservoirs experience water level fluctuations that control survival of their biota. I explored diverse but related aspects of water-level management. Three frameworks were indentified for directing rule curve (i.e., daily targets for water levels) changes in flood-control reservoirs managed by the U.S. Army Corps of Engineers (USACE), with differing scopes and requirements. Framework choice depends on the reservoir’s primary authorization and magnitude of the contemplated change. Changes without congressional approval must be based on flood risk. Quantile regression was used to model a maximum water level with a user-specified level of risk. Because actions that request changes to water levels from natural resource professionals should have a sound ecological basis, I analyzed the relationships between water level fluctuations and vegetation in reservoirs. Remote sensing methods were used to calculate a greenness index from vegetation in the reservoir based on 14 years of satellite imagery and water levels.