OCCURRENCE OF LEAD POISONING 
Waterfowl deaths attributed to lead poisoning have been reported from practically all sections of 
the United States. A list of localities where lead poisoning has been known to afflict waterfowl includes 
Delaware Bay, Delaware; Pamlico Sound, Virginia; the coast of North Carolina; Houghton Lake, Michi- 
gan; Lake Erie marshes, Ohio; Hovey Lake, Indiana; Green Bay, Wisconsin; the Illinois River valley, 
Illinois; Forney Slough, Iowa; Dalton Cutoff, Chariton County, Missouri; Claypool Reservoir, Arkansas; 
Catahoula Lake and the coastal marshes of Vermilion Parish, Louisiana; Sand Lake, South Dakota; Boyd 
Lake, Colorado; Bear River marshes, Utah; Snake River valley, Idaho; and Nehalem Bay, Oregon. 
Most of the reported losses from lead poisoning have occurred during late fall or winter; however, 
appreciable losses from lead poisoning have occurred among diving ducks during the spring. 
Outbreaks. -- Spor2dic die-offs of waterfowl from lead poisoning increase in number and severity 
as the birds tend to concentrate on heavily shot-over areas where abundance of food‘on bottoms entices 
the birds into intensive feeding. They occur usually at or near the end of the hunting season when the 
supply of shot pellets is abundant and before the pellets have penetrated deep into the muck or have been 
covered by a layer of silt. Lack of availability of certain wild foods, often at this time restricted by ice 
and snow, constitutes a factor that may also account for the local and seasonal nature of outbreaks of 
lead poisoning in waterfowl. 
Almost every year in the past 12, we have found wild ducks in Illinois that were disabled or dead 
from lead poisoning. Most spectacular losses have occurred after the end of the hunting season, when 
ducks have moved from refuges to heavily shot-over areas to feed. With the subsequent freezing weather 
of midwinter, the effect of lead poisoning has been brought into sharp focus, for large numbers of the 
ailing birds have moved into relatively small open-water areas where dead and dying ducks could 
be readily observed. 
The largest recorded outbreak of lead poisoning among Illinois ducks occurred near Graftonin 
January, 1948. There were about 110,000 ducks, most of them mallards, wintering in the area. Soon 
after the end of the hunting season on November 27, they moved from Swan Lake, a United States Fish 
and Wildlife Service refuge, to a public shooting ground, known locally as Stump Lake. Evidently, in 
feeding upon seeds in the bottom silt of the shallow water area, many mallards picked up lead shot. A 
few weeks later, with the lake almost completely frozen over, Edward Davis, Refuge Manager, began to 
notice sick mallards on the ice and seeking concealment in the shore-line vegetation, fig. 8. Autopsy 
revealed lead shot in the gizzard of nearly every duck examined. A tally of the dead ducks revealed that 
= 110) 
. 
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