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Significance of lead residues in mallard tissues

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Abstract

Tissues of adult, lead-dosed mallards that either died or were sacrificed were analyzed for lead. Lead levels in brains, tibiae, and breast muscle of ducks that died and in tibiae of ducks that were sacrificed increased significantly from dosage until death. Lead in the heart, lung, and blood from sacrificed ducks decreased significantly from dosage until death. Lead concentrations in tissues from ducks in the two groups were not significantly different except for the liver, kidney, and lung. Average lead levels in the livers and kidneys of ducks that died were significantly higher than those in ducks that were sacrificed. The mean concentration of lead in the lungs of the ducks sacrificed was significantly higher than the mean level in the lungs of ducks that died. Measurements of the lead concentrations in this study, when compared with lead levels reported in the literature for avian and non-avian species, showed that arbitrary diagnostic levels indicating lead poisoning could be set. In mallard ducks, lead levels exceeding 3 ppm in the brain, 6 to 20 ppm in the kidney or liver, or 10 ppm in clotted blood from the heart indicated acute exposure to lead.

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1974. Significance of lead residues in mallard tissues. https://pubs.usgs.gov/publication/ssrw182

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USGS1982

Changes in vegetation structure in seeded nesting cover in the prairie pothole region

A sample of 365 stands of seeded nesting cover (mixtures of cool-season grasses and legumes) was studied in the glaciated prairie pothole region during 1977-79. Measurements of species composition, canopy cover, plant height, and visual obstruction values differed with stand age but only in a general way when results from over the entire region were pooled. Maximum values for plant height and visual obstruction occurred once per stand during the first 10 growing seasons. Although the year of maximum growth was variable and unpredictable, stands showed trends of degeneration in height and visual obstruction after the year of maximum growth.Seeded nesting cover grew similarly throughout the region when on soils of capability class IV or better and within a precipitation range of 30 to 61 cm. Precipitation was the factor that most affected stand growth, especially the amount received in the year before spring measurements. Height and visual obstruction values within a stand were also directly affected by some individual species and by the percentage of grass within a stand. In 2 of the 3 study years, the height and visual obstruction values of residual cover were extremely reduced by ice pack, heavy snow pack, or a combination of snow pack and harvest by rodents. Such events, if frequent, largely negate the possibility of using minimum visual obstruction or plant height measurements for assessing quality of vegetation for wildlife cover and management purposes.Species composition, number of species, and canopy cover varied most during the first three growing seasons and least during the next six. Succession toward dominance by native grasses and forbs and woody species was retarded by the predominance of the species of seeded nesting cover, at least during the first 10 growing seasons.All stands had at least one species present that was either a noxious weed, a problem cropland weed, or a nuisance weed. Weeds were usually local in distribution. Five weed species needing special management attention on public lands are leafy spurge (Euphorbia podperae), wormwood (Artemisia absinthium), Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), and plumeless thistle (Carduus acanthoides). Sites disturbed by mammal diggings or those skipped during planting operations became revegetated mostly with species other than those of seeded nesting cover.Successfully established stands on good sites provided substantial food and cover for wildlife for at least 6 years and retained stand composition for at least 10 years. Further study will be necessary to determine longevity of these stands. Except for mandatory noxious weed control, no management treatments of seeded nesting cover were necessary before the seventh growing season, at which time some stands needed renovation. The primary goals for management of seeded nesting cover should be stand quality and longevity. Guidelines to these goals are suggested.

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