poisoning, throughout North America, is less serious than previously thought -- with the possible excep- 
tion of such species as the redhead, the numbers of which have been seriously depleted in recent years. 
The proportion of wild drake mallards held under artificial conditions of captivity that died from 
the effects of one shot pellet each generally exceeded that of birds dosed with one shot each and released 
in the wild. It is thought that the higher mortality rate may be largely because the penned mallards had 
no choice of food other than that provided. 
INFLUENCE OF DIET 
Experimental feeding of penned ducks showed that food has an important influence on the effect of 
lead shot ingested by waterfowl. 
Influence of Nutritional Properties. -- Chemical analyses made in the Department of Animal 
Science, University of Illinois, of several of the foods fed to lead-dosed ducks in early experiments sug- 
gested that certain nutritional properties tended to alleviate the effects of lead. Attempts were made to 
simulate diets containing these nutritional properties by adding, as supplements to whole corn, protein, 
calcium, phosphorus, calcium phosphate, or vitamin C. The results of these experiments did not corre- 
late well with results of the early experiments. It is evident that nutritional constituents alone probably 
are not responsible for the moderating influence of certain diets om lead poisoning. 
Influence of Physical Form. -- Experiments with captive mallards indicate that the effect of in- 
gested lead is influenced by the physical form of food in the diet, fig. 15. The harmful effect of ingested 
lead was most evident in the birds fed on whole corn, preferred by fall iicreanine mallards in Illinois. 
It was less evident in the birds fed on seeds of smaller size, such as wheat, tame rice, smartweed, and 
wild millet. It was still less evident in birds, feeding on corn or on corn and small grains, to whose diet 
was added the green parts of such aquatic plants as sago pondweed, duck weed, and coontail, figs. 16 and 
17. It was least evident in those birds fed on commercial duck pellets, which, upon coming into contact 
with moisture, break down into a soft mash. 
The influence of physical form was clearly shown when one group of game-farm mallards dosed 
with lead shot was fed whole corn and another corn ground to a meal. By the end of the third week, the 
group on whole corn had suffered a greater reduction in food consumption, higher weight losses, and a 
higher mortality rate than the group fed corn meal. 
Influence of Food Preference. -- Captive wild mallards dosed with lead showed different degrees 
oH Tiere 
