a. Corn and added supplements of one or more important nutritional elements failed to furnish 
a satisfactory substitute for natural foods of similar constituents in alleviating lead poisoning among 
penned waterfowl. 
b. Penned ducks fed on food items of small size and the succulent parts of aquatic water- 
fowl food plants were affected less by lead poisoning than those fed on food items of large size and 
greater hardness. 
c. Some penned mallards and Canada geese suffering from lead poisoning increased their 
chances for survival when they shifted their food preferences to smaller and softer food items. 
d. Symptoms of lead poisoning failed to appear in lead-dosed, penned mallards that maintained 
a normal rate of food intake. The amount of food consumed varied with sex and age, and the effect of 
ingested lead varied accordingly. 
12. Captive wild mallards showed individual differences in tolerances to lead doses. These dif- 
ferences seemed to be related to corresponding differences in the amounts of food consumed under 
normal conditions. 
13. Increasing the shot dose (within the limit of four pellets) administeredto penned mallards was 
found (1) to increase the proportion of ducks affected, (2) to increase the rate of mortality, but (3) not to 
increase the severity of symptoms nor (4) to shorten the survival period of poisoned ducks. 
14, Some severely affected penned mallards apparently recovered from lead poisoning following 
elimination of shot or renewal of appetite. 
15. Lead-induced starvation appeared to be the immediate cause of death in lead-poisoned mallards. 
16. Of the three metallic components (lead, arsenic, and antimony) of commercial shot, lead was 
found to be the only one to produce ill effects when fed to ducks. 
17. With the effects of commercial shot used as a standard, lead-magnesium, lead-calcium, lead- 
tin-phosphorus, and copper-coated lead-shot pellets were evaluated in the search for a possible means 
of eliminating or reducing lead-poisoning losses among waterfowl. None showed promise under the 
conditions of these experiments. Iron shot was found to be nontoxic to penned mallards, but this shot 
is not now available commercially. 
18. At the present time only stopgap measures can be undertaken to reduce wild waterfowl losses 
Eom lead poisoning. The following remedial measures are suggested: (1) Increase the amounts of 
certain natural waterfowl food plant resources, (2) disperse waterfowl from known focal areas of lead 
poisoning, (3) exercise greater care in shooting and thereby reduce the cripple loss as well as the 
amount of expended lead pellets deposited on the feeding grounds of waterfowl. 
5 eS 
