| Summary: | 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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