Browsing by Subject "Playas -- Texas"
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Item A time budget study of green-winged teal wintering on the Texas High Plains(Texas Tech University, 1982-08) Quinlan, Eileen ElizabethThe Southern High Plains of Texas contain 20,000-30,000 playa lakes. These ephemeral wetlands are the second-most important wintering habitat for waterfowl in the Central Flyway; in years of adequate rainfall they may support 1 million ducks. However, this area is intensively cultivated, with irrigation demands depleting the Ogallala Aquifer at rates exceeding its recharge. The ground water depletion has prompted farmers to modify playa basins for water storage, in turn reducing littoral zones and their biological productivity. Because green-winged teal (Anas crecca carolinensis) especially utilize playas as winter habitat in the Central Flyway, this study reports their behavior and energy demands on the Southern High Plains. The behavioral ecology of green-winged teal wintering on the playa lakes of the Southern High Plains of Texas was investigated using diurnal time budget data from September 1981 to March 1982. No differences (P >0.05) in activity patterns occurred between males and females. All activities showed differences (P <0.0001) across 6-week seasons. Aquatic feeding was highest during September-October (23.0%) indicating that green-winged teal supplement a nutritionally incomplete diet of corn during periods of molting and fat deposition. Resting was the primary activity throughout the winter, reaching a peak (66.9%) in the coldest season of December-January. Presumably, green-winged teal are adapted to arrive on their wintering area in early fall when excess productive energy is available to engage in energy costly activities and to meet the demands of molting and fat deposition prior to winter. There is then a shift to less costly activities (i.e., resting) with the onset of cold weather. Green-winged teal also exhibited distinctive daily activity cycles. Courtship and locomotion were highest (P <0.0001) during early morning, resting was highest (P <0.001) during late morning and afternoon, and feeding was highest (P <0.001) during late afternoon. The influences of several environmental variables were tested, with ambient temperature showing the most correlations with activities. Management recommendations for green-winged teal include maintaining winter habitat on playas by, 1) restriction of extensive basin modifications, 2) curtailment of grazing and agricultural activities near edges of playa, 3) encouraging the catchment of irrigation runoff.Item Aspects of the ecology and management of pheasants in the High Plains of Texas(Texas Tech University, 1983-05) Whiteside, Richard WhittingtonNot availableItem Black-tailed prairie dog association with playa lakes in the southern High Plains and a new approach to estimating colony population sizes(Texas Tech University, 2004-08) Pruett, Alison LNot availableItem Effects of tebuthiuron on characteristic playa lake algae of the Southern High Plains: a microcosm study(Texas Tech University, 1986-12) Price, David JohnWith use of tebuthiuron on pastures and rangelands, the possibility of adverse environmental effects on playa ecosystems has increased. Runoff from tebuthiuron-treated areas could provide an inflow of the herbicide into playas, where it accumulates in sediments. Tebuthiuron may affect algal populations in playas, thus reducing the amount of food available to invertebrates and various wildlife species. The objective of this research was to determine the impacts that tebuthiuron had on 11 algal species, which were treated at the beginning and end of the increase of algal growth. The two treatments represented inflow of water from rainfall into playas. The objective was accomplished by interpreting the dynamics of algal communities in one-phase microcosms treated with 0.18 ppm tebuthiuron. Variables monitored included cell numbers, cell volume, concentrations of photosynthetic pigments, composition of algal communities, and changes in available nutrients. Differences between control and treatment means of these variables were determined with least significant difference (LSD) tests after a significant (P <0.05) analysis of variance. Total alkalinity and pH increased during the study. Differences between control and first treatment means were observed for pH and total alkalinity. Dissolved oxygen increased and carbon dioxide decreased indicating that photosynthesis occurred in the microcosms. Inhibition of carbon dioxide levels were related to the herbicidal inhibition of photosynthetic pigments. An increase in total alkalinity resulted in decreased hardness, due to precipitation of metal salts. The decrease in hardness affected buffering capacities. Nitrification caused decreased nitrate levels, due to conversion of ammonia to nitrite. Nitrate and nitrite exhibited significant differences between control and treatment means for the the first treatment. Chloride levels increased while orthophosphate decreased indicating use by algal cells. Chloride and orthophosphate means were not different between control and first treatment. However, chloride means were different between control and second treatment. The only species affected by tebuthiuron was Bracteacoccus minor; however, as a community, the algae were inhibited by tebuthiuron. Packed-cell volume and photosynthetic pigment levels increased during the study; however, inhibition by tebuthiuron was detected in treated samples. No significant conclusions were drawn from the treatment at the end of the increase of growth, due to variability in the data. It was concluded that 0.18 ppm tebuthiuron, applied before growth increase, inhibited the algal community tested.Item Field-feeding ecology of waterfowl wintering on the Southern High Plains of Texas(Texas Tech University, 1982-08) Baldassarre, Guy AThe ecology of field-feeding dabbling ducks wintering on the Southern High Plains of Texas was studied on a 50 km2 study area in Castro County, from September-March 1979-82. Ducks relied primarily on waste corn that averaged 364 ± 12 kg/ha/field. Fields harvested at 14-21% moisture lost more than twice the corn as fields harvested at 22-36% moisture. Therefore, moisture content of corn at harvest provided a useful measure to predict initial waste. Waste cornfields underwent a variety of agricultural treatments that affected the abundance and availability of waste corn to waterfowl. Burning stubble maximized abundance and availability, whereas deep plowing reduced abundance by 97%. Disking and grazing reduced abundance by 77% and 84%, respectively. However, landowners tended to graze cattle on fields where initial waste was high and thus substantial amounts of waste corn remained when grazing was terminated. Manual salvage by migrant workers removed 58*^ of initial corn waste. Field-feeding waterfowl conducted 2 flights daily to cornfields near playa lakes where the birds concentrated. The average morning flight was initiated 52 ± 1.5 min before sunrise and terminated in 23 ± 1.4 min. The average evening flight began 25 ± 2.0 min after sunset and terminated in 37 ± 4.2 min with duration increasing as the season progressed. Dabbling ducks fed longer and participated more in evening as compared to concurrent daily morning flights. Minimum temperatures were correlated negatively with duration of evening flights, but not morning flights. There was no correlation between the amount of waste corn in, or the condition of, a field selected by feeding ducks with duration or initiation of feeding flights. However, the amount of corn present was correlated negatively with duration of the evening flight. Snowfall was positively correlated with duration of evening flights, but not morning flights. Feeding flocks selected fields based on an abundance/availability hierarchy, apparently attempting to minimize foraging time. Burned fields were preferred most when available, followed by disked fields, especially those containing >60 kg waste corn/ha. Field-feeding is an adaption to widespread agriculture, but also is a learned response to changes in wetland habitats.Item Habitat prereferences of breeding waterfowl on the Texas High Plains(Texas Tech University, 1978-05) Rhodes, Mark J.A study to determine waterfowl breeding habitat preferences on the Llano Estacado was undertaken from May to September 1977. A brood site survey of 37 playas was conducted in Castro, Floyd, Hale, and Swisher counties to find out the playa lake type preferred by brooding hens. Biweekly surveys of eight playa lakes in Castro and Swisher counties were conducted to determine physico-chemical characteristics of playa lake water, macroinvertebrate populations, vegetative characteristics and their relationships to brood use of individual playas. Brooding hens in the four surveyed counties preferred natural playa lakes (8l percent use) to mechanically modified playas. However, mechanically modified playas with extensive littoral zones received about six times as much use as modified playas with no littoral zone. A step-wise regression analysis showed that the area of emergent vegetation over 0.5 m tall, height of emergent vegetation over 0.5 m tall and lake turbidity could account for 99.2 percent of the variation in brood use from one playa to another. This study suggests that waterfowl production on the Texas High Plains can be markedly increased by manipulating playa lakes to encourage the taller emergent plant species and by preservation of shallow water zones in playa lake basins.Item Infiltration through playa lake basin soils(Texas Tech University, 1990-12) Koenig, Gregory PaulNot availableItem Numerical response of wintering waterfowl to macrohabitat in the southern High Plains of Texas(Texas Tech University, 1982-12) Obenberger, Susan MPopulations of pintails (Anas acuta), American wigeon (A. americana) , mallards (A. platyrhynchos) , and green-winged teal (_A. crecca) were studied on 10 23.04-km^2 plots in the Southern High Plains of Texas during September-March 1980-1981 and 1981-1982. Peak total populations occurred in November and February, largely because of massive influxes of pintails during these months. Mallard and wigeon populations were relatively stable after peak numbers arrived on the wintering areas and before spring migration. Sex ratios observed in this study were similar to those reported in other portions of the Southern High Plains. The estimated percentage of males was similar (P>0.05) each month during October-March for mallards and wigeon but was lower (P_< 0.05) in December 1981 (58%) than in January 1982 (70%) for pintails and in October-November 1980 (47-49%) than in December-March 1980-1981 (72-80%) for green-winged teal. Availability of waste corn in disced fields was relatively constant throughout the winter because as fields were plowed the stubble in other fields was disced. Less than 3% of the corn stubble was burned. Multiple regression models that predicted monthly waterfowl use of plots based on hectares of macrohabitat were acceptable for total ducks, wigeon, and pintails but were not acceptable for mallards and green-winged teal. Hectares of water, corn, and wheat positively affected waterfowl use whereas hectares of sorghum, cotton, and other land uses negatively affected waterfowl use. The models can be used to determine the most effective and cost-efficient management measures to increase or decrease waterfowl populations on wintering areas in the Southern High Plains of Texas.Item Population Ecology and Genetics of the Eastern Cottontail Rabbit on West Texas Playa Basins(Texas Tech University, 1982-08) Scribner, Kim ThomasSpatial and temporal changes in population number, density distribution, and genetic attributes of eastern cottontails (Sylviligus floridanus) were studied on 2 playa lake basins in the Texas Panhandle. Live-trapping was conducted from February through November, 1981, resulting in 1,857 captures of 931 individuals in the course of 7450 trap nights. Seven successive litters were produced on both areas from late March through early September, 1981. Prereproductive populations were estimated at 8.2 and 11.6 cottontails/ha on playa basins A and B respectively. Subsequent monthly estimates of population numbers and densities varied with reproductive increment and dispersal, which was related to crop phenology and harvest. Animals were concentrated during periods of limited cover and flooding. A sign;ificantly (P<0.05) high proportion of individuals were found on playa peripheries prior to new spring growth and during periods of dispersal than on playa basin interiors. Surrounding wheat and cotton fields provided cover and forage for dispersing animals, causing playa densities to decrease. Population increases were noted after crop harvest. Little change in adult and juvenile mortality rates occurred throughout the study, except during periods of dispersal. Spatial and temporal changes in allele frequency, genotypic proportions, and total and single locus heterozygosity were studied on both playa basins. Prereproductive adult cottontail populations had observed genotypic proportions that deviated significantly from expected Hardy-Weinberg equilibrium, seemingly the result of heterozygote deficiencies related to differential overwinter selection and/or nonrandom genotypic dispersal. These findings are inconsistent with previous studies in which heterozygosity increases were shown to correlate with superior fitness characteristics. Significant (P_<0.05) changes in population allele frequencies, genotypic proportions, and heterozygosity were related to population demographic characteristics. Apparent random matings by individual parental genotypes and subsequent juvenile recruitment dampened or eliminated the disequilibrium in Hardy-Weinberg proportions. Changes in population number due to reproductive recruitment and dispersal were accompanied by changes in gene frequency and heterozygosity. Spatial differences in population genetic attributes were maintained between the two playa basins throughout the study because of the large distances between breeding groups. However, parallel trends were observed in population genetic and demographic characteristics on both playa basins.Item Spatial analysis of playas on the Texas High Plains(Texas Tech University, 2004-12) Quillin, John PNot availableItem The macrofauna of two West Texas playa lakes with special reference to their use as biological indicators(Texas Tech University, 1978-12) Merickel, Frank WatsonTwo playa lakes, located in Lubbock county, were sampled weekly from initial filling through complete drying to determine the species composition and seasonal development of macrofauna. Information obtained was used to calculate diversity index values and assess the feasibility of using macroinvertebrates as biological indicators of pollution. Sixty-four species were collected in one or more developmental stages. Insects, particularly Hemiptera, became numerically cominant by the third week of filling while Crustacea were generally poorly represented. The potential application of biological indicators is thought to be greatest utilizing species of Crustacea. Faunal lists compiled by Sublette and Sublette (1967), Parks (1975) and this study support the observation that Crustacea are scarce in playa lakes surrounded by agricultural farmland. Results of extensive toxicological tests by Sanders (1969, 1970) suggests a causal relationship between agricultural runoff and the distribution of Crustacea in playa lakes. The species composition and seasonal development of insects is too variable from year to year to allow generalizations concerning their usefulness as biological indicators.