Geology topics

G.A. Swanson

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

22 records · Page 2Linked to original sources

USGS1975

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↗

USGS1973

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↗

USGS1973

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↗

USGS1972

Production and standing crop of Hexagenia (Ephemeroptera) in a large reservoir

Population dynamics of the mayflies, Hexagenia limbata (Serville) and Hexagenia bilineata (Say), were studied in Lewis and Clark Lake from 1962 to 1969. Nymphs that hatched in June and July emerged as adults in 13-14 months (titled 1-year cycle) and nymphs hatched in late August or September emerged in 22 months (titled 2-year cycle). Although an estimated 79% of the newborn nymphs begin life in the 2-year cycle group, only 53% of the emergent adults were in this group because of mortality. Standing crop was highest in the shore area, although a major migration away from the shore occurred in the spring. This migration was most intense when the population density exceeded 100/m2. Biomass ranged from 260 to 1070 mg/m2 dry weight over the study period. Instantaneous emergence rates were higher than predatory mortality rates but were only operative from about 1 July to 15 September.Production was estimated by two methods from extensive sampling in 1964 on a 1256 hectare section of the reservoir. The growth method yielded 1.50 gm/m2 dry weight and the Hamilton method, 1.67 gm/m2. The turnover ratio of 2.81 calculated from these data multiplied by the standing crop over the rest of the reservoir resulted in an average annual production of 15.6 kg/hectare for the reservoir.The Hamilton method was applied to less extensive collections from 1964 to 1969. Maximum production occurred in 1966 at 2.41 gm/m2.

Studies in Natural Sciences↗