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G.A. Swanson

Publications and source records attributed to G.A. Swanson.

18 recordsLinked to original sources

Changes in atmospheric circulation patterns affect midcontinent wetlands sensitive to climate

Twenty-seven years of data from midcontinent wetlands indicate that the response of these wetlands to extremes in precipitation-drought and deluge-persists beyond the extreme events. Chemical changes transcend such simple relations as increased salinity during dry periods because drought provides mechanisms for removal of salt by deflation and seepage to groundwater. Inundation of vegetation zones including rooted or floating mats of cattail (Typha glauca) can stimulate sulfate reduction and shift the anion balance from sulfate to bicarbonate dominance. Disruptions in the circulation of moisture-laden air masses over the midcontinent, as in the drought of 1988 and the deluge of 1993, have a major effect on these wetlands, which are representatives of the primary waterfowl breeding habitat of the continent.

Limnology and Oceanography

Coleoptera species inhabiting prairie wetlands of the Cottonwood Lake Area, Stutsman County, North Dakota

The aquatic Coleoptera of a prairie wetland complex in Stutsman County, North Dakota, were collected from April 1979 to November 1980. Identification of 2594 individuals confirmed 57 species, including seven new records for North Dakota. Two seasonally flooded and two semipermanent wetlands, totaling 7.43 ha, contained 53% of the Dytiscidae, 43% of the Haliplidae, 38% of the Hydrophilidae, and 22% of the Gyrinidae species previously identified from North Dakota. Although 49.1% of the Coleoptera species occurred in both types of wetlands, the occurrence of 29 species varied by wetland class.

Prairie Naturalist

Prairie basin wetlands of the Dakotas: a community profile

This description of prairie basin wetlands of the Dakotas is part of a series of community profiles on ecologically important wetlands of national significance. The shallow wetlands of the Dakotas form the bulk of the portion of the Prairie Pothole Region lying within the United States. This region is famous as the producer of at least half of North America's waterfowl and an unknown, but large, proportion of other prairie-dwelling marsh and aquatic birds.The wetlands described here lie in relatively small, shallow basins that vary greatly in their ability to maintain surface water, and in their water chemistry, which varies from fresh to hypersaline. These wetlands occur in a wide variety of hydrological settings, in an area where annual and seasonal precipitation varies greatly in form and amount. Thus the presence of surface water in these wetlands is largely unpredictable. Superimposed on these phenomena are the effects of a variety of land uses, including pasture, cultivation, mechanical forage removal, idle conditions and burning. All those factors greatly affect the plant and animal communities found in these basins.This profile covers lacustrine and palustrine basins with temporarily flooded, seasonally flooded, and semipermanently flooded water regimes. Basins with these water regimes compose about 90% of the basins in the Prairie Pothole Region of the Dakotas. This profile outlines the wetland subsystems, classes and subclasses that occur in these basins, and provides a useful reference to their geologic, climatic, hydrologic, and pedologic setting.Detailed information on the biotic environment of the wetlands dealt with in this profile will be useful to scientists and resource managers. Special recognition is paid to the macrophyte and invertebrate communities, which have dynamic qualities found in few other of the world's wetland ecosystems.The most noteworthy animal inhabitants of these basins are waterfowl, which are a resource of international concern. Because of the importance of this resource, much research on the habitat use and feeding ecology of breeding waterfowl has been conducted in the region. These topics receive special attention in this profile.The Prairie Pothole Region is a major world supplier of cereal grains. Consequently, wetlands in the region are often drained for crop production or otherwise cropped when water conditions permit. These practices degrade the value of wetlands for most species of wildlife and conflict with the aims of conservationists. The subject of human uses and impacts to prairie wetlands is thus an important part of this profile.

Biological Report

Agricultural chemicals and prairie pothole wetlands: Meeting the needs of the resource and the farmer -- U.S. perspective

Included are the reasons for concern over the effects of agrichemicals (pesticides and fertilizers) on prairie-pothole wetlands in the United States. Summarized are the results of studies conducted to date on this topic. Identified is additional research needed to assess the impacts of agrichemicals on these wetlands. Included is a discussion of management strategies and initiatives which we believe may minimize inputs of these chemicals and their impacts on wetlands and waterfowl within this portion of the prairie pothole region, while still meeting the needs of the agricultural community.

Transactions of the North American Wildlife and Na

Agricultural chemicals and the quality of prairie-pothole wetlands for adult and juvenile waterfowl - What are the concerns?

A review of the literature and results of ongoing studies indicates that the potential for agricultural chemicals, particularly aerially-applied insecticides, to enter prairie potholes and reduce the quality of these wetlands for waterfowl is great, and that a coordinated effort by farmers, wildlife managers, and regulatory agencies is needed to minimize these impacts

Biological Report

Renesting Characteristics of Captive Mallards on Experimental Ponds

Renesting characteristics of captive wild-strain mallards (Anas platyrhynchos) were investigated on experimental ponds in southcentral North Dakota during the breeding seasons of 1976-81. Renesting efforts and egg production increased during the 1st 3 years. Post-yearling females that experienced clutch loss during early incubation produced 3 clutches of eggs during the breeding season. All of the birds produced 4 clutches and 50% produced 5 during the study. Birds provided with an unlimited food supply produced an average of 10.36 ± 1.03 (SD), 9.97 ± 1.09 (SD), 9.59 ± 0.91 (SD), 8.47 ± 0.94 (SD), and 8.50 ± 0.50 (SD) eggs during each successive nesting attempt. Clutch size differed (P < 0.01) among birds, ages, and nesting attempts. Renesting intervals for mallard females on unlimited food averaged 7.13 ± 1.24 (SD) days and ranged from 5 to 10 days. Intervals differed (P < 0.01) among birds and interval sequences. When food availability was reduced, renesting intervals increased and clutch size decreased.

North Dakota

Potential impacts of agricultural chemicals on waterfowl and other wildlife inhabiting prairie wetlands: An evaluation of research needs and approaches

The potential for agricultural chemicals to enter prairie-pothole wetlands and impact wildlife dependent on these wetlands for survival and reproduction appears to be great. However, the actual risk to wetland wildlife from the inputs of these chemicals cannot be adequately assessed at this time, because of insufficient data. Available data on the use of pesticides in the prairie-pothole region and the toxicity of these pesticides suggest that insecticides pose the greatest hazard to wetland wildlife, particularly birds. The majority of the most widely used insecticides within the region are very toxic to aquatic invertebrates and birds. Of particular concern are the impacts of agricultural chemicals on the quality of the remaining wetlands in the region and whether or not these impacts have contributed to observed declines in waterfowl populations. Although existing data suggest that adult and juvenile waterfowl may not be more sensitive to these chemicals than are other wetland wildlife, their food habits and feeding behaviors may make them more vulnerable to direct toxic effects or chemical-induced changes in the abundance of aquatic invertebrates. Laboratory and field studies in the United States and Canada are critically needed to assess these potential impacts.

Transactions of the North American Wildlife and Na

Fall foods of migrant common snipe in North Dakota

Studies of foods consumed by common snipe ( Capella gallinago ) during fall migration (Sperry 1940, Erickson 1941, Choate in Tuck 1972, Tuck 1972) have shown that diets vary among habitats. More recently, Fogarty and Arnold (1977) expressed the need for more detailed information on snipe food habits and more refined knowledge of the snipe's range and adaptability to various food situations. There is a paucity of information on snipe feeding ecology in the prairie pothole region of North America where unstable and unpredictable hydrological conditions affect abundance and availability of aquatic foods. The objectives of study were to (1) identify foods consumed by common snipe during fall migration in south-central North Dakota, and (2) describe changes in diet during years with different water regimes.

North Dakota

Feeding ecology of breeding gadwalls on saline wetlands

The feeding ecology of breeding gadwalls ( Anas strepera ) from saline wetlands in North Dakota was examined in relation to sex, pair mates, reproductive status, food availability, and wetland type during the spring and summer of 1971 and 1972. Esophagi of males and females contained 40.4 and 48.2 percent animal food, respectively, between 17 April and 25 August. Animal foods consumed by paired females varied with reproductive condition and were independent of their mates. Invertebrates increased from 47.7 i?? 17.4 percent in the diet during prelaying to 72.0 i?? 18.4 percent during laying and declined to 46.3 i?? 30.0 percent during postlaying. Aquatic insects dominated the diet during egg-laying and were selected disproportionately relative to their availability. Esophageal contents indicated that diversity of plant and animal foods in the diet varied inversely with specific conductance. Major factors influencing food selection of the breeding birds are discussed as interactions among their physiological status, their anatomical and behavioral characteristics, and the abundance and behavior of food organisms as influenced by chemical and physical features of the environment. The data suggested that these interrelated ecological factors act simultaneously to control the phenology of events and determine the foods utilized.

North Dakota

Some nutritional aspects of reproduction in prairie nesting pintails

The nutritional significance of invertebrate foods in the diet of breeding hen waterfowl during the period of egg formation is discussed. Proximate, elemental, and amino acid analyses of the principal foods consumed by hen pintails ( Anas acut ) during the nesting season indicate the animal foods selected are rich sources of protein and calcium, whereas plant foods tested were low in protein, particularly in the essential amino acids lysine and methionine. Calcium content in major plant foods was far below needs considered adequate for egg production. Studies with penned, hand-reared pintails indicated the inadequacy of wheat as the dietary staple during breeding. Egg production among pairs on the control diet differed significantly from that of the wheat plus oystershell (P < 0.05) and wheat (P < 0.01) diets. Pairs fed wheat during the breeding period experienced nearly complete reproductive failure. The poor reproductive response among hens on the diet of wheat plus oystershell suggested that calcium availability was not the only factor limiting productivity.

Journal of Wildlife Management

Mercury residues in pintails breeding in North Dakota

Livers of 42 pintail hens ( Anas acuta ) breeding in eastern North Dakota during the spring and early summer of 1969 and 1970 were analyzed for total mercury by the neutron activation technique. Mercury content on a wet weight basis ranged from 0.055 ppm to 9.512 ppm and averaged 0.888 ± 1.796 ppm (SD). Liver mercury levels of hens collected in early spring (prior to planting of crops) were significantly lower than those of hens taken late in the nesting season ( P < 0.01). Mercury residues among prelaying, laying, and postlaying groups collected following the onset of spring planting did not differ significantly ( P > 0.05). Albumen mercury residue was correlated with liver mercury content (r = 0.756, P < 0.05). Mercury content in livers of five wild juveniles averaged 0.123 ± 0.074 ppm.

North Dakota

Chemical stability of preserved oligotrophic water samples

Tests were conducted to determine whether changes that may occur in the chemical characteristics of stored oligotrophic waters collected on 15 sites in northeastern Minnesota were affected by chloroforming. Chloroform was added on site to one of each pair of samples to stabilize the organic content of the water by preventing biological decomposition. The samples were subsequently stored at 25 deg.C, and pH and specific conductivity were measured at intervals for a period of 13 months at which time nine additional chemical parameters (total dissolved solids, total alkalinity, chloride, sulfate, silica, calcium, magnesium, sodium and potassium) were measured.pH increased and specific conductivity decreased. Average changes occurring in time from the original levels were not influenced by treatment, and first differed significantly (P<0.05, paired t test) at 14 days for pH and 8.5 months for specific conductivity. Total dissolved solids and sulfate were significantly (P<0.01 and <0.05, respectively) larger in treated than untreated samples after 13 months storage while the reverse was true for calcium (P<0.05). Total alkalinity, chloride, silica, and magnesium, however, did not differ significantly (P>0.05). Sodium and potassium levels were too low to provide meaningful comparisons. It was concluded that chloroform may be advantageous in preserving oligothrophic waters with respect to total dissolved solids, sulfate and calcium.

Proceedings of the North Dakota Academy of Science