Postbreeding ecology of the redhead duck (Aythya americana) was studied on Lake Winnipegosis from 1974-1977. / Daily energy expenditure, including energy for activities and molt, showed little seasonal variation. Expenditures for molt were reduced by temporally staggering molt in different feather tracts. Redheads conserved energy through behavioral adaptations and by compensating higher demands with reduced expenditure elsewhere. / Plant material comprised 92 and 98% of the dry aggregate weight of food consumed by males and females. Drought in 1977 influenced distribution of redheads through its' effect on submergent vegetation. / Body molt of pennaceous feathers in tracts II, III, and IV exhibited a bimodal pattern indicative of basic and alternate feather generations in males. Tracts I and VI molted irregularly, and tract V molted once coinciding with the single down molt. Prebasic molt was advanced in most tracts with the earlier termination of breeding during drought, whereas the prealternate molt was unaffected. / Little annual variation in timing of wing molt in males occurred, suggesting that this molt was under photoperiodic control. Upper-wing coverts were molted gradually to provide protection to the exposed wing. / Digestive organ size in males fluctuated seasonally in response to diet quality, quantity, and innately with predictable events. Changes in the gastro-intestinal tract at the beginning of molt were related to enhanced protein uptake. / The concept of a labile protein reserve was applicable to seasonal variability in the size of proteinaceous tissues. Greater food intake correlated with higher tissue weights, whereas lower intake and increased protein demand caused a reduction in tissues. Skeletal muscles contributed most to the reserve. Reserves were drawn on throughout the flightless period to meet protein requirements. / Lipids were stored in the abdominal cavity, on mesenteries of the small intestine, and in the subcutaneous depot, which was also the largest. Total fat content in males was lowest during breeding and averaged 8 to 9% of body weight at the onset of wing molt. Total fat varied inversely with body water content, and independently of fat-free carcass weight. Foraging time explained 81% of the variation in seasonal lipid levels.

Thesis (M.S.)--Ohio State University. / Bibliography: leaves 117-123. Available online via OhioLINK's ETD Center

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / Title from title screen (viewed May 27, 2009 ). Includes bibliographical references. Online version of print original.

Thesis (Ph. D.)--University of Wisconsin, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 52-54).

The mallard is the most important species of North American waterfowl; its breeding range has been reduced and is in danger of a further reduction due to agricultural and drainage practices. To maintain mallard populations at the present level, it will be necessary to control and manage sufficient habitat to provide for their needs. In such a program, the knowledge of the food habits of waterfowl is an essential tool. The objectives of this study were: to determine the spring and summer foods of the mallard, and to determine the relationship between utilization and availability of the various foods. A study of the spring and summer food habits of mallards was conducted from 1957 to 1959 on a 100 square mile study area in south central Manitoba. 211 adult and 135 young mallards were collected for analyses of stomach contents. At the same time, ponds were randomly selected from the study area for examination and analyses of faunal and vegetative characteristics. In the determination of food habits, the gullet contents proved superior to the gizzard contents. The animal foods found in the gizzard were partially digested and could not be measured accurately. There was also the possibility that the hard seeds of aquatic plants persist in the gizzard for a long period of time. The spring and summer foods of adult mallards consisted of 45.7% plant material and 54.3% animal material. The young mallards, on the other hand, consumed 9.0% plant and 91.0% animal foods. In both adult and young birds the Class Insects provided the main source of animal foods, and in both cases, the majority of the insect foods were obtained from the orders Trichoptera and Diptera. In adult mallards the important plant foods were obtained from the G-ramineae and Chenopodiaceae families. A difference.in the feeding habits of adult male and female mallards was found. The male birds consumed more plant foods and less animal foods than did the female birds. Pond fauna increased in abundance until a peak was reached in midsummer then decreased in numbers. On the other hand, seeds increased in abundance in late summer and decreased the following spring as germination took place. The proportion of plant and animal foods consumed by adult mallards varied with the availability of these foods; the importance of plant foods in their diet decreased during the summer, whereas, the importance of animal foods increased. Considerable variations in water levels, from flood to drought conditions, were experienced during the study. As a result of the change in water levels, the amount of emergent vegetation decreased. The food of young mallards reflected this change in habitat; the ratio of plant to animal foods consumed decreased from 1957 to 1959. The animal protein intake of the mallard is variable and the variations in the consumption of animal and plant foods depend upon their availability. The relative proportions of the various foods eaten may not be of primary importance; mallards appear to be able to balance their diets with widely different kinds of food. / Science, Faculty of / Zoology, Department of / Graduate

From September, 1951, until March 1952, field work was carried on to determine the distribution of wintering diving ducks on the coastal waters of southern British Columbia, and an attempt was made to discover and evaluate the factors causing distribution and movement. Diving ducks are influenced by the availability of food and other factors related to this availability. These factors include salmon and herring spawning, grain elevators, sewer outfalls, and changing tides. Local movements result from courtship activity, diel periodicity and disturbing agencies. Mortality factors, including hunting, oiling, predation and lead poisoning did not cause serious Inroads in the wintering diving duck population during the study. Lake, and bay and estuarine habitats were found to be less important wintering areas than habitats along protected and unprotected coastline. All species of diving ducks showed preference for certain habitats and regions in the study area, and were absent or uncommon in others. During the winter, the drakes and hens of most species were distributed non-randomly because of the preponderance of males and their tendency to flock together. In early spring the sexes were distributed non-randomly due to pair formation and predominance of drakes. A differential sex migration was evident in most species of ducks during late fall and early spring. Only a small percentage of juveniles of all species were wintering on the study area, indicating that they possibly winter in other localities. / Science, Faculty of / Zoology, Department of / Graduate

Macroscopic examinations of ducks in a hunter kill sample for the presence of ingested lead shot pellets in the gizzards indicated that a slight increase in active lead poisoning since 1947, had taken place among mallards (Anas platyrhynchos) and that a more severe increase had occurred in pintails (Anas acuta). Instances of proventriculii stuffed with food occurred only in conjunction with a diet of oats or wild seed. Quantitative analysis of bone and liver ash by means of a specially designed dithizone-chloroform method was carried out to determine lead contents and their significance. Analysis showed that a considerable number of ducks of both species, though proportionately more mallards than pintails were survivors of past contamination by lead and that, under normal conditions of weather and availability of food and perhaps other factors, the death toll attributable to plumbism should not equal the active leading percentages obtained by gizzard examination. Pintails appeared to suffer more, both in terms of actual incidence of leading as well as their apparent inability to offer as much resistance as mallards, to the effects of lead. Though there appeared, in mallards, to be no significant difference in the probability of ingesting lead shot and the survival expectancies between the sexes in juvenile ducks, a lower survival of adult females was recorded. A lower survival was also recorded in juvenile mallards as compared to the adults. Adverse weather conditions, probably expressing themselves as an effect on the availability and quality of food, appeared to give lead poisoning an opportunity to exert greater influence. Although the current lead deposition taking place in any one year appears to be responsible for marked increases in the incidence of lead poisoning, evidence indicated that lead shot is also available to ducks either on the nesting grounds or on the hunting grounds from the deposition of previous years. / Science, Faculty of / Zoology, Department of / Graduate

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