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Fig. 10. -- Percentage of waterfowl populations carrying ingested commercial shot pellets in autumn and 
early winter. Data for six regions of the United States are based upon an examination of 22,071 gizzards 
collected in recent years. 
The proportion of ducks that swallow shot while feeding, as revealed by examination of gizzard 
contents, varies among the different species, fig. 11, indicating that lead poisoning losses may be higher 
for some kinds of ducks than for others. Whether they are actually higher can be determined only 
by further study. 
The great difference between the less than 1 per cent of the gadwalls and the more than 13 per cent 
of the redheads swallowing lead shot suggests a basic relationship between the quantity of ingested shot 
and the feeding traits and habitat of each kind of waterfowl. It seems likely that relatively few gadwalls 
and baldpates swallow shot because they feed on leafy plants rather than on seeds in the bottom soil. 
Shovelers and green-winged teals feed on mud flats and in shoal water areas where they apparently skim 
the surface rather than puddle into the bottom silt. Probably in feeding on the surface they come into 
contact with lead less frequently than do mallards and pintails, both of which have been found to puddle 
6 inches or more through the bottom silt for food. Blue-winged teals, which apparently puddle more than 
do green-wiriged teals, have a higher proportion of gizzards containing shot, even though the blue-wings 
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