Dale D. Humburg

Flooding to Restore Connectivity of Regulated, Large-River Wetlands Natural and controlled flooding as complementary processes along the lower Missouri River

You can always count on finding the Mississippi just where you left it last year. But the Missouri is a tawny, restless, brawling flood. It cuts corners, runs around at night, fills itself with snags and traveling sandbars, lunches on levees, and swallows islands and small villages for dessert. Its perpetual dissatisfaction with its bed is the greatest peculiarity of the Missouri.... It makes farming as fascinating as gambling. You never know whether you are going to harvest corn or catfish (Fitch 1907, p. 637).

Further evidence of biases associated with hunter-killed mallards

Assessment of waterfowl management strategies depends upon data that evaluate hypotheses that mallards (Anas platyrhynchos) killed by hunters are similar to those in the general population. Moreover, data are needed to provide further insight into mallard molt progression, the apparent influence of body mass on survival, and direct and indirect mortality caused by lead shot ingestion. Thus, we compared body mass, percentage completion of the prealternate molt, and presence of lead shot in gizzards between mallards killed by hunters (hunter-killed) and those concurrently collected by researchers (researcher-collected) from the free-living population in the Mingo Basin of southeastern Missouri. Researcher-collected mallards were heavier (P < 0.05) than hunter-killed mallards of the same age and sex

Quantitative and qualitative approaches to identifying migration chronology in a continental migrant

The degree to which extrinsic factors influence migration chronology in North American waterfowl has not been quantified, particularly for dabbling ducks. Previous studies have examined waterfowl migration using various methods, however, quantitative approaches to define avian migration chronology over broad spatio-temporal scales are limited, and the implications for using different approaches have not been assessed. We used movement data from 19 female adult mallards (Anas platyrhynchos) equipped with solar-powered global positioning system satellite transmitters to evaluate two individual level approaches for quantifying migration chronology. The first approach defined migration based on individual movements among geopolitical boundaries (state, provincial, international), whereas the second method modeled net displacement as a function of time using nonlinear models. Differences in migration chronologies identified by each of the approaches were examined with analysis of variance. The geopolitical method identified mean autumn migration midpoints at 15 November 2010 and 13 November 2011, whereas the net displacement method identified midpoints at 15 November 2010 and 14 November 2011. The mean midpoints for spring migration were 3 April 2011 and 20 March 2012 using the geopolitical method and 31 March 2011 and 22 March 2012 using the net displacement method. The duration, initiation date, midpoint, and termination date for both autumn and spring migration did not differ between the two individual level approaches. Although we did not detect differences in migration parameters between the different approaches, the net displacement metric offers broad potential to address questions in movement ecology for migrating species. Ultimately, an objective definition of migration chronology will allow researchers to obtain a comprehensive understanding of the extrinsic factors that drive migration at the individual and population levels. As a result, targeted conservation plans can be developed to support planning for habitat management and evaluation of long-term climate effects.

Landscape effects on mallard habitat selection at multiple spatial scales during the non-breeding period

Previous studies that evaluated effects of landscape-scale habitat heterogeneity on migratory waterbird distributions were spatially limited and temporally restricted to one major life-history phase. However, effects of landscape-scale habitat heterogeneity on long-distance migratory waterbirds can be studied across the annual cycle using new technologies, including global positioning system satellite transmitters. We used Bayesian discrete choice models to examine the influence of local habitats and landscape composition on habitat selection by a generalist dabbling duck, the mallard (Anas platyrhynchos), in the midcontinent of North America during the non-breeding period. Using a previously published empirical movement metric, we separated the non-breeding period into three seasons, including autumn migration, winter, and spring migration. We defined spatial scales based on movement patterns such that movementsxa0>0.25 andxa0<30.00xa0km were classified as local scale and movementsxa0>30.00xa0km were classified as relocation scale. Habitat selection at the local scale was generally influenced by local and landscape-level variables across all seasons. Variables in top models at the local scale included proximities to cropland, emergent wetland, open water, and woody wetland. Similarly, variables associated with area of cropland, emergent wetland, open water, and woody wetland were also included at the local scale. At the relocation scale, mallards selected resource units based on more generalized variables, including proximity to wetlands and total wetland area. Our results emphasize the role of landscape composition in waterbird habitat selection and provide further support for local wetland landscapes to be considered functional units of waterbird conservation and management.

The Social Organization of a Mallard Population in Northern Iowa

Twenty-two hen and 134 drake mallards were marked during a 2-year study of mallard (Anas platyrhynchos) breeding activity on Ventura Marsh in north-central Iowa. During April, sex ratios of mallards observed on breeding areas (54% drakes) were lower than those observed in fields or on open water areas (58% drakes). Numbers of mallards observed declined after the initial influx, and remained relatively constant throughout the breeding season. The number of breeding mallards appeared to be limited by pursuit flights. Sixty-four marked drakes, observed at least once with a hen spent an average of 17.6 days on the marsh whereas 70 drakes, not seen with hens averaged 1.3 days on the area. There was a continual turnover of lone drakes on the study area throughout the breeding season. The nests of 22 marked hens were destroyed between day 10 and 17 of incubation. Four of the hens left the study area, 3 remained but did not remate, and 15 remated. Of 11 identified rematings, 8 hens (73% ) returned to their original drake and 3 (27%) changed drakes after losing their nest. J. WILDL. MANAGE. 42(1):72-80 The social organization of mallard breeding populations is not clearly understood. Studies concerning courtship behavior, interaction between pairs, and nesting provide a base for understanding mallard mate selection and production. The pair is fundamental to mallard reproduction. Weidman and Darley (1971) reviewed the range of attitudes among investigators concerning the role of the mallard male and female in display and courtship. They concluded that the female is essential in directing display and that social display promotes pair formation, which occurs for the most part before spring migration (Hawkins in Hochbaum 1944:121; Weller 1965:227). Hochbaum (1944:16) and Sowls (1955:21) reflected the general acceptance by biologists that most mallards are paired upon arrival at spring breeding areas. Lebret (1961:105) defined a hen and drake as paired when they maintained close proximity when together and when the drake defended the female from other mallards. Pair interaction in the form of pursuit flights (3-bird flights) was described by Dzubin (1957), McKinney (1965) and Titman (1973). Pursuit and avoidance were believed responsible for the spacing of breeding pairs (Dzubin 1969a). The ultimate consequence of spacing appears to be a lessened competition for breeding requisites and dispersion of nests as an antipredator mechanism. Those pairs unable to enter a breeding system may attempt to est elsewhere, delay the breeding effort, or molt. During the reproductive effort, drakes were observed with hens on breeding areas throughout the laying period and for an average of 8 days into incubation (Lebret 1961:127). Dzubin (1955:286) reported drakes present in the vicinity of nests until day 14 of incubation. Unless the nest is destroyed or abandoned, the hen continues incubating until the eggs hatch. Nest destruction, which appears to be a limiting factor in the annual production of mallards, was reported by Dzubin and Gollop (1972) to 1 Support provided by Iowa Conservation Commission P-R Project W-115-R-2 and the Michigan Agricultural Experiment Station; Journal Article Number 7689. 2 Present address: Missouri Department of Conservation, Fish and Wildlife Research Center, Columbia 65201. 72 J. Wildl. Manage. 42(1):1978 This content downloaded from 157.55.39.215 on Tue, 30 Aug 2016 05:35:26 UTC All use subject to http://about.jstor.org/terms MALLARD SOCIAL ORGANIZATION * Humburg et al. 73 range from 22 to 73 percent, depending upon the area studied, nesting cover condition, predator density, water level, weather, and human disturbance. Renesting, as high as 77 percent (Keith 1961:67), plays an important role in maintaining annual production in breeding mallard populations. A pair bond is necessary for successful culmination of egg laying and clutch incubation (Dzubin 1970), so hens losing nests probably will not renest without remating, even though they can lay fertile eggs up to 17 days after insemination (Elder and Weller 1954:501). Renesting hens could select a drake from a variety of sources; the original mate, a drake originally paired with a different female, or a previously unpaired drake. Although few data are available concerning the breeding activity of unpaired drakes, Titman (1973:41) observed marked unpaired males for a short time in localized areas on a breeding marsh. He speculated that there may be a selective advantage for an unpaired drake to be available for breeding with renesting hens. Elder and Weller (1954) suggested that unpaired drakes are essential to high productivity by supplying mates to renesting hens. In studying pintails (Anas acuta) Smith (1968) found that pursuit flights may often result in rape of the female, insuring fertilization. However, unpaired drakes could be harmful to production by harrassing nesting hens (Titman and Lowther 1975). Investigations by Bellrose (1961) revealed mallard sex ratios generally favor drakes and ranged from 68 to 233 drakes: 100 hens, depending upon latitude, season, and data collection method. The percentage of drake mallards appears to have increased since 1970 (Bellrose 1976:230). Some biologists have advocated harvest of the excess drakes. Dzubin (1970) suggested that harvest of surplus drakes may be biologically justified if (1) no difference exists in the time required for sexual maturity in both sexes, (2) surplus drakes have no significance in providing mates for renesting hens, and (3) harvest of hens would not parallel drake harvest. With the advent of the point system in waterfowl hunting regulations, which allows for the harvest of surplus drakes, controversy has arisen concerning the biological implication that increased drake harvest could have on mallard production. This study was designed to describe the structure and relationships between various components of a mallard breeding population on a breeding area. Specifically, the breeding activity of drake and hen mallards relative to the nesting cycle of unsuccessful nesting hens is described. We gratefully acknowledge the assistance of V. Wright with the project design, E. Peloquin and B. Batt for assistance with methods and data analysis, and G. Dudderar and D. Beaver for evaluating the final manuscript. Field assistance was provided by T. Willson, A. Woodward, R. Andrews, and

How will predicted land use change affect waterfowl spring stopover ecology? Inferences from an individual‐based model

Summary nHabitat loss, habitat fragmentation, overexploitation and climate change pose familiar and new challenges to conserving natural populations throughout the world. One approach conservation planners may use to evaluate the effects of these challenges on wildlife populations is scenario planning. nWe developed an individual-based model to evaluate the effects of future land use and land cover changes on spring-migrating dabbling ducks in North America. We assessed the effects of three Intergovernmental Panelxa0on Climate Change emission scenarios (A1B, A2 and B1) on dabbling duck stopover duration, movement distances and mortality. We specifically focused on migration stopover duration because previous research has demonstrated that individuals arriving earlier on the nesting grounds exhibit increased reproductive fitness. nCompared to present conditions, all three scenarios increased stopover duration and movement distances of agent ducks. nAlthough all three scenarios presented migrating ducks with increased amounts of wetland habitat, scenarios also contained substantially less cropland, which decreased overall carrying capacity of the study area. nSynthesis and applications. Land-use change may increase waterfowl spring migration stopover duration in the midcontinent region of North America due to reduced landscape energetic carrying capacity. Climate change will alter spatial patterns of crop distributions with corn and rice production areas shifting to different regions. Thus, conservation planners will have to address population-level energetic implications of shifting agricultural food resources and increased uncertainty in yearly precipitation patterns within the next 50xa0years.

Species Associations and Habitat Influence the Range-Wide Distribution of Breeding Canada Geese (Branta canadensis interior) on Western Hudson Bay

Abstract. n Inter- and intra-specific interactions are potentially important factors influencing the distribution of populations. Aerial survey data, collected during range-wide breeding population surveys for Eastern Prairie Population (EPP) Canada Geese (Branta canadensis interior), 1987–2008, were evaluated to assess factors influencing their nesting distribution. Specifically, associations between nesting Lesser Snow Geese (Chen caerulescens caerulescens) and EPP Canada Geese were quantified; and changes in the spatial distribution of EPP Canada Geese were identified. Mixed-effects Poisson regression models of EPP Canada Goose nest counts were evaluated within a cross-validation framework. The total count of EPP Canada Goose nests varied moderately among years between 1987 and 2008 with no long-term trend; however, the total count of nesting Lesser Snow Geese generally increased. Three models containing factors related to previous EPP Canada Goose nest density (representing recruitment), distance to Hudson Bay (representing brood-habitat), nesting habitat type, and Lesser Snow Goose nest density (inter-specific associations) were the most accurate, improving prediction accuracy by 45% when compared to intercept-only models. EPP Canada Goose nest density varied by habitat type, was negatively associated with distance to coastal brood-rearing areas, and suggested density-dependent intra-specific effects on recruitment. However, a non-linear relationship between Lesser Snow and EPP Canada Goose nest density suggests that as nesting Lesser Snow Geese increase, EPP Canada Geese locally decline and subsequently the spatial distribution of EPP Canada Geese on western Hudson Bay has changed.

Do economic values and expenditures for viewing waterfowl in the U.S. differ among species

ABSTRACT Many economic studies value birdwatching in general and often do not account for potential differences in viewers’ benefits from observing different species. But, how different are economic values of viewing various bird species? To answer that question, we surveyed Ducks Unlimited (DU) members using an online questionnaire to estimate trip expenditures and consumer surplus per trip for viewing pintail ducks, waterfowl in general, and other species of waterfowl. Expenditures per trip were USD

The role of protected area wetlands in waterfowl habitat conservation: Implications for protected area network design

231,

Survival and Homing of Female Mallards

199, and