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Geology topics

Gary L. Krapu

Publications and source records attributed to Gary L. Krapu.

At least 73 records · Page 4Linked to original sources
USGS1979

Age determination of mallards

A technique for distinguishing adult from yearling wild mallards ( Anas platyrhynchos ), from late winter through the nesting season, was developed by applying discriminant analysis procedures to selected wing feather characters of 126 yearlings and 76 adults (2-year-olds) hand-reared from wild eggs during 1974, 1975, and 1977. Average values for feather characters generally increased as the birds advanced from yearlings to adults. Black-white surface area of greater secondary covert 2 was the single most reliable aging character identified during the study. The error rate was lowest in females (3%) when discriminant functions were used with measurements of primary 1 weight and black-white area of greater secondary covert 2 and in males (9%) when the functions were used with black-white area of greater secondary coverts 1, 2, and 3. Methodology precludes aging of birds in the field during capture operations.

North Dakota↗
USGS1979

Use of prairie pothole habitat by breeding mallards

Detailed information on the use by mallards ( Anas platyrhynchos ) of prairie pothole habitat during the nesting season is necessary to interpret habitat needs of the species during the breeding period. Many data have been collected and published relating pair counts to habitat use and water conditions (e.g., Evans and Black 1956; Smith 1971; Stoudt 1971; Stewart and Kantrud 1973, 1974). However, use of pair-count data to assess wetland use tends to emphasize individual wetland units and does not consider total wetland habitat required to sustain a breeding pair on a daily or seasonal basis. We therefore attempted to determine habitat use by individually radio marked mallards during the breeding period. This paper describes home range characteristics and habitat use of a radiomarked sample of mallard hens breeding in North Dakota during 1973-75. Time budget data are also presented for 2 marked pairs of mallard pairs of mallards.

North Dakota↗
USGS1979

Marsh nesting by mallards

Nest-site selection by mallard (Anas platyrhynchos) hens was studied on a 52-km2, privately owned area in the Missouri Coteau of south-central North Dakota during 1974-77. Sixty-six percent of 53 nests initiated by radio-marked and unmarked hens were in wetlands in dense stands of emergent vegetation and usually within 50 m of the wetland edge. These findings and other sources of information suggest that significant numbers of mallards breeding in the Prairie Pothole Region nest in marsh habitat. Potential factors contributing to mallard use of marsh habitat for nesting purposes are discussed. Management considerations associated with marsh nesting by mallards are described and research needs are identified.

Wildlife Society Bulletin↗
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↗
USGS1974

Foods of breeding pintails in North Dakota

Food habits of breeding pintails ( Anas acuta ) were studied relative to sex, land use, and reproductive condition during the spring and summer of 1969, 1970, and 1971 in eastern North Dakota. Hens and drakes, respectively, consumed 79.2 percent and 30.0 percent animal matter on nontilled wetlands and consumed 16.6 percent and 1.1 percent animal matter on tilled wetlands. Aquatic dipterans (primarily larval forms), snails, fairy shrimp, and earthworms accounted for 71 percent of the diet of hens on nontilled wetlands, while barnyard grass ( Echinochloa crusgalli ) seeds formed 71 percent of the diet of hens on tilled wetlands. Cereal grain seeds formed 84 percent of the diet of 10 hens feeding on cropland. The diet of hens was influenced by reproductive status. Animal foods were predominant during the laying period (77.1 percent) but were less important in the postlaying diet (28.9 percent). Invertebrates formed 83.9 percent of the diet of renesting hens, 61.0 percent were dipteran larvae and snails. High consumption of animal foods during egg formation presumably is related to invertebrates being superior to plants in providing certain nutrients required for production of viable eggs. Research findings suggest that food requirements of prairie-nesting pintails can be met most effectively by providing pairs access to shallow, nontilled wetland habitat subject to periodic drawdowns.

North Dakota↗
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↗