Browsing by Subject "Waterfowl"
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Item Aspects of the ecology and hunting economics of migratory waterfowl on the Texas High Plains(Texas Tech University, 1980-05) Moore, Richard L.The High Plains of Texas is dotted with numerous playa lakes which are used in agriculture as a source for irrigation water and as tailwater catchment basins. Waterfowl use these playa lakes during migration and many overwinter on them. While waterfowl are the most obvious wildlife encountered on playas, this wetland habitat is used by a number of other avian and mammalian species (Appendix A). Bolen et al. (197 9) pointed out that playas offer the only waterfowl habitat in this highly agriculturalized area of Texas. Considerable amounts of time and money have been spent on playa modification research for water conservation but little or no consideration has been given to wildlife until the last few years. Dwindling wetland resources throughout the nation have focused a new emphasis on ecological research on playa lakes (Simpson et al. 1980, Stormer et al. 1980).Item Chufa (Cyperus esculentus) management and use by migratory birds in the middle Rio Grande Valley, New Mexico(Texas Tech University, 2000-08) Taylor, John PaulNatural wetlands provide food resources for a variety of migratory birds. Although much is known regarding the production of aboveground food resources, comparatively less is known regarding the production of underground food resources such chufa (Cyperus esculentus") tubers. In addition, studies demonstrating the utilization of underground food resources by migratory birds are lacking. In 1996 and 1997, chufa tuber production and use by migratory birds were compared among mowing, discing, and sustained flooding treatments at Bosque del Apache National Wildlife Refuge, New Mexico. In addition to chufa, Johnson grass (Sorghum halepense), field bindweed (Convolvulus arvensis), and total underground production were compared. Aboveground plant composition, standing crop, and seed mass were also compared among treatments. Finally, the utilization of underground food resources by waterfowl and sandhill cranes (Grus canadensis) during winter flooding was measured by comparing paired open and exclosed sampling points in each treatment.Item Effects of cattail management on invertebrate production and migratory bird use of Cheyenne Bottoms, KS(Texas Tech University, 2002-12) Kostecke, Richard MichaelDense monotypic cattail (Tvpha spp.) stands are a management problem in many prairie wetlands as they exclude desirable plants and migratory wetland birds. Cheyenne Bottoms Wildlife Area (CBWA), a Wetland of International Importance located in central Kansas, has experienced a large increase in cattails and a subsequent decrease in avian use. As a consequence, intensive cattail management is practiced at CBWA. However, dense emergent vegetation also influences production of Invertebrates, an important food source for migratory wetland birds. Effectiveness of different techniques in reducing cattail at CBWA was assessed from fall 1999 to spring 2001. Cattail management also was evaluated based on its impacts on invertebrate production and migratory wetland bird use and behavior. In addition, aquatic invertebrate succession (i.e., temporal patterns in density, biomass, familial richness, familial diversity, and trophic structure) and migratory wetland bird community structure (i.e. nestedness and species co-occurrence patterns) also were assessed. Treatments to reduce cattail (i.e., burned, control, disked, and grazed) were applied at CBWA during 1999 and 2000. Disking and high-intensity grazing (20 head/11.05 ha) resulted in the lowest cattail densities and biomass. Reduction of cattail within these treatments lasted for at least 1 year. In the short term, cattail management by disking and high-intensity grazing was at the expense of higher plant species richness, plant species diversity, and non-cattail productivity. Within 1 year, however, plant species richness, plant species diversity, and non-cattail productivity had recovered (i.e., increased) in the disked and high intensity-grazed treatments. The more heavily vegetated burned and control treatments had greatest invertebrate production. However, maintaining large stands of such vegetative cover to benefit invertebrates is counter to migratory bird management goals at CBWA. While invertebrate food resources may be greater in areas of greater vegetative cover, such areas exclude most wetland birds. It should be noted, that while invertebrate production was lower in the more open disked and grazed treatments, invertebrate densities were adequate (> 100/m^) to support some migratory wetland bird use within these treatments. However, invertebrate densities were generally < 1600/m^ within all cattail management treatments. Invertebrate densities of 5000/m^ may be needed to support large (0.5 million birds) populations of migratory wetland birds at CBWA. Aquatic invertebrate succession patterns, including temporal patterns in trophic structure, following inundation at CBWA were assessed in order to understand the controls on aquatic invertebrate assemblage structure. Invertebrate density, biomass. familial richness, and familial diversity generally increased following inundation. Detritivores were rapid colonizers of newly flooded wetland habitat and were always the most abundant trophic group. Herbivores were most abundant during later successional stages. Predators followed a bimodal distribution with both early and late peaks. The early peak in predators was attributable to the presence of macroveliids. Predators also became more abundant during later successional stages. Although abundance of herbivores and predators increased over time, detritivores were always the most abundant trophic group at CBWA. Aquatic invertebrate succession has been hypothesized to occur in 3 phases (Lake et al. 1989, Schneider and Frost 1996, Moorhead et al. 1998). Increasing densities, biomass, familial richness, and familial diversity of aquatic invertebrates at CBWA are consistent with the first phase of succession, colonization and establishment. Familial richness and diversity generally stabilized within 2 weeks following Inundation, however, suggesting that the invertebrate assemblage at CBWA had entered the second phase of succession. This phase is characterized by the increasing influence of competition and/or predation, which prevents richness and diversity from increasing further. Aquatic invertebrate assemblages at CBWA failed to reach the third phase of succession dominated by predation. Temporal differences in trophic structure did not exist. Detritivores were always the dominant trophic group at CBWA. Failure to reach an assemblage dominated by predators may be related to timing of inundation. Studies of aquatic invertebrate succession have generally followed succession beginning with spring/early summer inundation. However, inundation occurred in late summer/early fall at CBWA. Abiotic factors (e.g., temperatures) and development of habitat structure (i.e., plant succession) are likely to differ between these time periods. Thus, controls on aquatic invertebrate assemblage structure are also likely to differ among these time periods. Therefore, the model of aquatic invertebrate succession posited by Lake et al. (1989), Schneider and Frost (1996), and Moorhead et al. (1998) may not hold for wetlands flooded in the fall. Greatest densities, species richness, and species diversity of migratory wetland birds were found in the disked and high-intensity grazed treatments. Foraging and resting were the most commonly observed behaviors. Foraging and resting behaviors generally did not vary among treatments, suggesting that the greatest difference among treatments in regards to migratory wetland bird use is the number of birds that can be accommodated. Treatments, such as the disked and high-intensity grazed, which had lower densities of cattail excluded fewer birds than treatments, such as the burned and control, which had higher densities of cattail. Models to predict migratory wetland bird species richness, species diversity, and densities were variable. However, results suggest that water depth is often an important variable influencing use by migratory birds. More species were accommodated at CBWA in spring 2001, when mean water depth was 12 cm. than in fall 1999 and 2000. when mean water depths were > 41 cm. In addition, high (5000/m^) densities of invertebrate prey may be needed to support large and diverse populations of migratory wetland birds. Vegetation variables included in models generally suggest that lightly vegetated and open areas should be maintained in order to increase migratory wetland bird use of CBWA. Such conditions were found in the disked and high-intensity grazed treatments, where migratory wetland bird species richness, species diversity, and densities were greatest. Nonrandom assemblages of migratory wetland birds exist at CBWA. In particular, nested patterns of species occurrence among cattail-management treatments have important conservation implications. Because assemblages in species-poor treatments (i.e., burned and control) were subsets of those found in species-rich treatments (i.e., disked and grazed) (i.e. assemblages were nested), effective cattail management can be applied without reducing overall migratory wetland bird species richness. Mutually exclusive (i.e. checkerboard) patterns of co-occurrence existed for many migratory wetland bird species pairs. Ecologically and morphologically similar species often did not co-occur (e.g., green-winged Anas crecca and blue-winged teal A. discors). However, such co-occurrence patterns are unlikely to be due to proximate competitive exclusion as the majority of associations among species pairs were positive. In most instances, checkerboard patterns of co-occurrence can probably be attributed to inter-specific differences in migration chronology. Disking and high-intensity grazing were effective means of reducing cattail for 1 year. Highest densities, species richness, and species diversity of migratory wetland birds also occurred in the disked and high-intensity grazed treatments. Cattail-management treatments exhibited a nested structure where the species found in little used treatments (i.e., burned and control) were subsets of those found in the highly used disked and high-intensity grazed treatments. This nested structure suggests that cattail management can be implemented without reducing overall species diversity. Because behavior did not vary among treatments, the largest difference among treatments in regards to migratory wetland bird use was in the number of birds that could be accommodated. Intensive cattail management did reduce invertebrate production; however, invertebrate production in disked and grazed treatments was presumably adequate (> 100/m^) to ensure use by migratory wetland birds.Item Experimental mass-marking of waterfowl wintering on the Southern High Plains of Texas(Texas Tech University, 1987-05) Godfrey, Ralph DThe use of fluorescent particles for marking waterfowl was assessed using captive mallards (Anas platyrhynchos), 30 July 1985 through 26 August 1986. Additionally, field studies were conducted November 1984 to March 1986 on the Southern High Plains of Texas. Wild waterfowl were captured November 1984 to March 1985 and October 1985 to March 1986. Caged mallards were in alternate plumage throughout most of the study. None of the feathers shed during molt had fluorescent particles adhering, thus m o U was not a limiting factor for determining the marked index on captive mallards. Captive mallards exposed to pigment solutions for 60 minutes marked equally well as ducks exposed for periods up to 480 minutes. The period of particle retention on plumage of captive mallards was highly correlated (P s 0.001) with the initial marked index of an individual (y = 4.24x, r^ = 0.94, df = 35). There were no differences between sexes in the period of particle retention. Wings of captive mallards retained fluorescent particles longer than other body regions. Application of 7 kg of fluorescent pigment/ha-m of water (3 lbs/ac-foot) was sufficient to mark waterfowl for 5 weeks. However, low marked indexes from 2 lakes suggested that waterfowl need to be examined soon after the initial pigment application to determine if additional pigments should be applied. The marked index was not influenced by sex or species for mallards, American wigeons (A. americana), northern pintails (A. acuta), and green-winged teals (Â. crecca). Waterfowl on lakes ^ 1 m in depth, and those not receiving feedlot runoff, had higher marked indexes than did waterfowl from other lakes. Unmarked waterfowl (n = 383), captured and confined in cages on lakes containing fluorescent pigments, received marked indexes highly correlated (P ^ 0.0001) with the concentration of fluorescent particles in water samples collected from within the cages (y=0.66x,r^2=0.67). The distribution of fluorescent particles throughout lakes was not affected by prevailing winds, but particles did sink. Lakes s 1 m in depth, and those not receiving feedlot runoff, maintained higher concentrations of particles over time than did other lakes. The average size of fluorescent particles did not change between weeks in each lake. Observers, with limited instruction, were capable of relatively accurate scoring of particles on waterfowl wings. Extent of observer experience with wildlife, waterfowl, or viewing fluorescent pigments had little effect on the accuracy of scoring wings. However, individuals with previous particle viewing experience could distinguish particles with greater ease than novice observers.Item Waterfowl impacts to zooplankton communities in wetland meta-ecosystems(2011-08) Johnston, Mary Kay, 1977-; Leibold, Mathew A.; Keitt, Timothy H.; Parmesan, Camille; Theriot, Edward; Troelstrup, NelsThe meta-ecosystem concept is an attempt to combine metacommunity, ecosystem and landscape ecology. In meta-ecosystems, both organismal dispersal and material movement between patches can have important effects on communities. This concept provides a more realistic framework of natural systems by considering both processes jointly. My dissertation presents a case-study of natural metaecosystems by studying the role of waterfowl in structuring zooplankton communities in prairie pothole wetlands in South Dakota. I use observations of natural wetlands, microcosm and mesocosm experiments to show how dispersal of materials and organisms by waterfowl can affect zooplankton abundance and community composition. Waterfowl are conspicuous, behaviorally adaptable, highly mobile and economically important members of wetland habitats. They are thought to have possible effects on zooplankton communities either by dispersing zooplankton propagules among wetlands or by moving nutrients into (via defecation) or out of (via consumption of macrophytes and invertebrates) wetlands. In this dissertation, I show evidence that waterfowl disperse a limited subset of locally rare zooplankton species between wetlands. I also provide experimental evidence that these dispersed species may have impacts on zooplankton community assembly. I also show how input of waterfowl excreta may sometimes have strong impacts on the local community. Very large inputs of goose excreta promote abundance and diversity of zooplankton. However, inputs at more modest levels, such as those routinely found in nature, are rarely detectible. Additions of excreta at levels five-times that typically found in nature produce a possible shift in zooplankton community structure away from both no-excreta communities and communities fertilized with comparable amounts of nitrogen and phosphorus. I postulate that most excreta quickly sinks to the benthos and only a small fraction becomes available for use by zooplankton. On the time scales used in my dissertation, it is only with very large additions of excreta that shifts in the zooplankton community become apparent. My dissertation is one of the first to apply the meta-ecosystem concept to a natural system. It also shows that waterfowl impacts on the zooplankton community may be most important in small wetlands or early in community assembly.