Ingestion of lead and nontoxic shotgun pellets by ducks in the Mississippi Flyway

We examined the extent to which ingested nontoxic (steel and bismuth-tin) shotgun pellets replaced toxic (lead) pellets in ducks harvested in the Mississippi Flyway during the 1996 and 1997 hunting seasons (fifth and sixth yr after nationwide conversion to nontoxic shot). Gizzards were collected from 16,651 ducks and processed for the presence of pellets. Prevalences of ingested pellets were 8.9% for 15,147 mallards (Anus platyrhynchos), 12.7% for 749 ring-necked ducks (Aythya collaris), 4.3% for 579 scaups (Aythya affinis and A. marila), and 9.7% for 176 canvasbacks (Aythya valisinerta). For gizzards with ingested pellets, as: much as 68% of mallard, 45% of ring-necked duck, 44% of scaup, and 71% of canvasback contained only nontoxic pellets. We estimated that nontoxic shot reduced mortality from lead poisoning in Mississippi Flyway mallards by 64%. Ingestion of greater than or equal to 2 toxic pellets declined by as much as 78%. To the extent that our findings apply to other species and flyways in North America, an estimated 1.4 million ducks in the 1997 fall continental flight of 90 million were spared from fatal lead poisoning. Only 1.1% of 1,318 gizzards positive for shot-is pellets came from ducks shot with toxic pellets, and only 1 toxic fishing sinker was found in the 16,651 duck gizzards.