Geology topics
Grey W. Pendleton
Publications and source records attributed to Grey W. Pendleton.
Habitat characteristics of American woodcock nest sites on a managed area in Maine
We measured characteristics of habitat near 89 nests of American woodcock ( Scolopax minor ) and 100 randomly selected points on Moosehorn National Wildlife Refuge, Calais, Maine, an area managed for woodcock. At nest sites, basal area was lower ( P < 0.001), densities of deciduous saplings were greater ( P < 0.001), densities of coniferous saplings were lower ( P = 0.001), densities of shrub stems were greater ( P = 0.002), and height of trees was shorter ( P = 0.001) than at random sites. Nest sites were closer to openings ( P < 0.001) than were random sites. Nests were in 15 cover types. The aspen ( Populus spp.), tamarack ( Larix laricina ), and alder ( Alnus rugosa ) types were used as nest sites more often than expected in relation to habitat types available at random sites ( P < 0.001). Fifty-eight percent ( n = 89) of nests were in stands of aspen, 11% in alder or tamarack, and 10% in mature second-growth gray birch ( Betula populifolia ) and red maple ( Acer rubrum ). Forty-four percent (n = 89) of the nests were in clearcuts <10 years old. Habitat characteristics around sites of first nests were not different among years ( P > 0.05) or between sites of successful nests and nests destroyed by predators, although the large variances of the variables reduced our power to detect differences. Habitat around sites of renests differed from sites of first nests. Sites around first nests had lower basal area of dead trees ( P = 0.05) and higher stem densities of aspen ( P = 0.03) and cherry saplings ( P = 0.001), and viburnum ( P = 0.05), while renest sites had taller trees ( P = 0.02). The change from nest sites in areas dominated by alders and tree-size gray birch used in 1977-80 to sites dominated by sapling trees, especially aspen, used during 1987-90 suggests that woodcock in the expanding population at the refuge are selecting nest sites created by habitat management since 1979.
Effects of diet on rate of body mass gain by wintering canvasbacks
Because habitat degradation has led to the loss of submerged vegetation in Chesapeake Bay, wintering canvasbacks ( Aythya valisineria ) have shifted from a plant diet of American wildcelery ( Vallisneria americana ) to an animal diet of Baltic clams ( Macoma balthica ). We conducted experiments with pen-reared canvasbacks ( n = 32, 1990; n = 32, 1991) to assess the effect of this diet change on mass recovery rate following a simulated period of food deprivation. During the recovery phase, canvasbacks were fed ad libitum either (1) Baltic clams (1991 only), (2) tubers of wildcelery, 3) corn, or (4) commercial control diet. Initial body mass of ducks did not differ between years ( P = 0.754) or among pens ( P > 0.264) or diets within years (1990, P = 0.520; 1991, P = 0.684). Body mass decline during food deprivation ( x̄ = 26.0 g/day ± 0.6 SE) did not differ among diets (1990, P = 0.239; 1991, P = 0.062) or between sexes in 1990 ( P = 0.197), but was greater ( P = 0.039) for males ( x̄ = 28 g/day ± 0.8 SE) than females ( x̄ = 25 g/day ± 0.9) in 1991. Mass recovery rate differed between diets (clams excluded) in 1990 ( P = 0.003) and 1991 (clams included) ( P = 0.011); mean = 42 g • bird -1 /day -1 ± 3.8 (SE) control diet, mean = 32 g • bird -1 /day -1 ± 2.8 wildcelery tubers, mean = 24 g • bird -1 /day -1 ± 4.9 whole corn, and mean = 23 g • bird -1 /day -1 ± 1.0 Baltic clams. Canvasbacks consumed an average of 2,169 g • bird -1 /day -1 of Baltic clams, 1,158 g • bird -1 /day- 1 of wildcelery tubers, 152 g • bird -1 /day -1 whole corn, and 208 g • bird -1 /day -1 (dry mass) control diet during recovery. Managers should restore and maintain aquatic plant foods that enhance winter survival of canvasbacks and other waterfowl in response to declining habitat quality.
Population modeling and its role in toxicological studies
A model could be defined as any abstraction from reality that is used to provide some insight into the real system. In this discussion, we will use a more specific definition that a model is a set of rules or assumptions, expressed as mathematical equations, that describe how animals survive and reproduce, including the external factors that affect these characteristics. A model simplifies a system, retaining essential components while eliminating parts that are not of interest. ecology has a rich history of using models to gain insight into populations, often borrowing both model structures and analysis methods from demographers and engineers. Much of the development of the models has been a consequence of mathematicians and physicists seeing simple analogies between their models and patterns in natural systems. Consequently, one major application of ecological modeling has been to emphasize the analysis of dynamics of often complex models to provide insight into theoretical aspects of ecology. 1
Habitat use at night by wintering American woodcock in coastal Georgia and Virginia
Nocturnal habitats used by American woodcock ( Scolopux minor ) were studied using radio telemetry at two coastal wintering sites in Georgia (1982-84) and Virginia (1991-92). In Georgia, use of forested habitats at night was extensive while use of fields at night varied between years but generally was low. We found no difference in the probability of moving to a field at night among the four age-sex classes ( P = 0.23). A significant effect ( P < 0.05) of age-sex class was noted between distances moved from diurnal to nocturnal locations in Georgia. Young females moved farther than any other age-sex class. In Virginia, no effect of age-sex class was found on the probability of being located during the night in either a field or a forest.
Survival rates of American woodcock wintering along the Atlantic coast
Because American woodcock ( Scolopax minor ) populations have been declining, we attached radio transmitters to woodcock at coastal plain sites to determine if survival during winter was involved in the decline. Sites were in Georgia (1982-84, 1989-92), South Carolina (1988-89), and Virginia (1991-92). Survival rates were not different between age or sex classes. Survival rates differed ( P = 0.003) among years. Daily survival rates were lowest ( P = 0.030, S = 0.987) during 1982-83 in Georgia and highest ( P = 0.004, S = 0.999) during 1990-91 in Georgia than in the other years and locations combined ( S = 0.996). We attributed all mortality to raptors and mammals. Compared with other periods of the year, winter was a time of low survival for woodcock. Lower survival rates were possibly a cause of population decline.
Interactive effects of selenium, methionine, and dietary protein on survival, growth, and physiology in mallard ducklings
Concentrations of over 100 ppm (100 mg/kg) selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Both quantity and composition of dietary protein for wild ducklings may vary in selenium-contaminated environments. Day-old mallard (Anas platyrhynchos) ducklings received one of the following diets containing 22% protein: unsupplemented (controls), 15 ppm Se (as selenomethionine), 60 ppm Se, methionine supplemented, 15 ppm Se with methionine supplement, or 60 ppm Se with methionine supplement. In a second concurrent experiment the above sequence was repeated with a protein-restricted (11%) but isocaloric diet. In a third concurrent experiment all ducklings received 44% protein with 0, 15, or 60 ppm Se added. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and histopathological lesions of the liver occurred. Antagonistic interactive effects occurred between supplementary methionine and Se, including complete to partial alleviation of the following Se effects by methionine: mortality, hepatic lesions, and altered glutathione and thiol status. With 11% protein, growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and methionine supplementation, although protective afforded less protection than it did with 22% protein. With 44% protein, ducklings experienced physiological stress, and Se was more toxic than with methionine-supplemented 22% protein. These findings suggest the potential for antagonistic effects of Se, methionine, and protein on duckling survival and physiology.
Interactive effects of arsenate, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings
High concentrations of arsenic (As) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a maJor source of protein for wild ducklings, may vary in environments that are contaminated with selenium. Dayold mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm Se (as selenomethionine), 60 ppm Se, 200 ppm As (as sodium arsenate), 15 ppm Se with 200 ppm As, or 60 ppm Se with 200 ppm As. In a concurrent experiment, the same sequence was repeated with a proteinrestricted (7%) but isocaloric diet. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and livers had histopathological lesions. Arsenic alone caused some reduction in growth. Antagonistic interactive effects occurred between As and Se, including complete to partial alleviation of the following Se effects: mortality, impaired growth, hepatic lesions and lipid peroxidation, and altered glutathione and thiol status. With 7% protein, survival and growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and As (200 ppm) caused mortality, decreased growth, and liver histopathology. These findings suggest the potential for antagonistic effects of Se and As on duckling survival, growth, and physiology with adequate dietary protein but more severe toxicological effects when dietary protein is diminished.
Nonresponse patterns in the Federal Waterfowl Hunter Questionnaire Survey
I analyzed data from the 1984 and 1986 Federal Waterfowl Hunter Questionnaire Survey (WHQS) to estimate the rate of return of name and address contact cards, to evaluate the efficiency of the Survey's stratification scheme, and to investigate potential sources of bias due to nonresponse at the contact card and questionnaire stages of the Survey. Median response at the contact card stage was 0.200 in 1984 and 0.208 in 1986, but was lower than 0.100 for many sample post offices. Large portions of the intended sample contributed little to the final estimates in the Survey. Differences in response characteristics between post office size strata were detected, but size strata were confounded with contact card return rates; differences among geographic zones within states were more pronounced. Large biases in harvest and hunter activity due to nonresponse were not found; however, consistent smaller magnitude biases were found. Bias in estimates of the proportion of active hunters was the most pronounced effect of nonresponse. All of the sources of bias detected would produce overestimates of harvest and activity. Redesigning the WHQS, including use of a complete list of waterfowl hunters and resampling nonrespondents, would be needed to reduce nonresponse bias.
Home range and movements of juvenile Puerto Rican parrots
We studied home range and movements of 15 radio-marked, juvenile Puerto Rican parrots ( Amazona vittata ) fledging from wild nests during summer and fall, 1985-87. When juvenile parrots remained in the nest valley, home ranges during 1986 ( x̄ = 32 ± 10 [SE] ha, n = 4) were larger ( P = 0.0079) than during 1987 ( x̄ = 13 ± 6 ha, n = 5). After radio-marked parrots integrated into adult flocks, home ranges during 1986 ( x̄ = 1,075 ± 135 ha, n = 3) were similar ( P = 0.10) to 1987 ( x̄ = 416 ± 62 ha, n = 2). Juvenile parrots restricted their movements to nest valleys an average of 58 ± 29 days following fledging. After joining adult flocks, juvenile parrots routinely flew between the east and west slopes of the Luquillo Mountains but did not exhibit a seasonal pattern of movement. We recommend that captive-raised, juvenile parrots used in release programs be ≥ 5 months old to ensure they are mature enough to integrate into wild flocks.
Selenium accumulation and elimination in mallards
Selenium accumulation and loss were measured in adult mallards ( Anas platyrhynchos ) fed selenomethionine during two experiments. In Experiment 1, both sexes were fed a diet containing 10 ppm selenium for 6 weeks, followed by 6 weeks on untreated feed. Selenium accumulation in liver and muscle of females was described by C=A(1−e −bt ). Concentrations of selenium were predicted to reach 95% of equilibrium faster in liver (7.8 days) than in muscle (81 days). The loss of selenium from liver and muscle of females was described by the exponential loss rate equation: C=Ae −bt , with half-times of 18.7 and 30.1 days, respectively. Males reached similar levels of selenium in liver and breast muscle as females and declined to similar levels once selenium treatment ended. In Experiment 2, females were fed increasing levels of selenium until some died. Survivors were switched to an untreated diet and selenium was measured in blood, liver, and breast muscle over 64 days. The same equation as in Experiment 1, C=Ae −bt , was used to describe the loss of selenium from blood and muscle. Halftimes were 9.8 and 23.9 days, respectively. For liver, the equation C C = A 1 e − b 1 t + A 2 e − b 2 t "> = A 1 e −b 1 t + A 2 e −b 2 t was used. Selenium initially decreased in liver by one-half in 3.3 days, with subsequent half-times of 3.9, 6.0, and 45.1 days.
Effects of organophosphorus insecticides on sage grouse in southeastern Idaho
Die-offs of sage grouse ( Centrocercus urophasianus ) were verified in southeastern Idaho in 1981. We captured 82 apparently healthy grouse to quantify the effects of organophosphorus insecticides (OP's) and other pesticides on sage grouse in sagebrush ( Artemisia spp.) bordering agricultural lands in July 1985 and 1986. Grouse were fitted with radio collars and tracked through part of each summer. At least 18% of 82 radio-tagged grouse in 1985-86 subsequently occupied fields at the time they were sprayed with OP insecticides dimethoate or methamidophos. Cholinesterase (ChE) assays of brains and residue analysis of crop contents indicated that 5 and 16% of the marked sample died from OP's in 1985 and 1986, respectively. Approximately 200 sage grouse were present in a block of alfalfa sprayed with dimethoate; 63 of these were later found dead and ChE activity in 43 brains suitable for assay were depressed >50%. Maximum residues in crop contents of dead grouse were 18 μg/g methamidophos and 30 μg/g dimethoate. Intoxicated or dead grouse were observed in or near 6 fields sprayed with dimethoate or methamidophos in 1985-86. Twenty of 31 intoxicated grouse radiotagged after being found in dimethoate-sprayed (1986) alfalfa died. Our study indicates that certain pesticides have the potential for adversely affecting grouse populations.