Effect of hunters' switch from lead to steel shot on potential for oral lead poisoning in ducks.

Mallards and black ducks (n = 409) killed by hunters during the 1980 and 1981 hunting seasons in Pennsylvania (Susquehanna River and Crawford County) were examined to evaluate the effectiveness of regulations that converted the studied areas from lead to steel shotgun pellets in 1977-1978. Gizzards were examined for ingested lead and steel shot, and liver specimens were analyzed for lead. Since there is no evidence to suggest that ducks preferentially ingest steel or lead shot, it was concluded that ducks with steel shot would have contained lead shot. Therefore, we concluded that the conversion to steel shotgun pellets accounted for the decreased prevalence of ingested lead shot from 11.2% to 5.6%. Toxic concentrations of lead (greater than or equal to 6 ppm, wet weight) in the liver were found in 6 of 23 ducks that contained lead shot, whereas only 2 of 386 ducks without lead pellets had toxic concentrations. It was concluded that the conversion to steel shotgun pellets in the studied areas probably has decreased the exposure of ducks to lead shot, thereby decreasing the potential for lead poisoning.