William L. Anderson

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 (Anas 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 valisineria). 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 ≥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-in pellets came from ducks shot with toxic pellets, and only 1 toxic fishing sinker was found in the 16,651 duck gizzards.

EFFECTS OF LEAD, IRON, AND BISMUTH ALLOY SHOT EMBEDDED IN THE BREAST MUSCLES OF GAME-FARM MALLARDS

Effects of five lead (Pb), iron (Fe), or bismuth (Bi)/tin (Sn) alloy shot embedded in the breast muscles of game-farm mallards (Anas platyrhynchos) were studied from 28 March 1994 through 27 March 1995. We detected no differences in the mean survival times, mean hematocrits, or mean body weights among the three shot types. Connective tissue encapsulated Pb and Bi/Sn shot but only slight changes occurred in tissues surrounding the shot. Recovered Pb and Bi/Sn shot were essentially unchanged in appearance and weight. A thin zone of “oxide” surrounded Fe shot with a slight inflammatory response and a small amount of scarring adjacent to the embedded shot. Fe shot decreased slightly in weight while embedded. Bacterial infections were absent in all dosed ducks. Mean weights of kidneys, livers, and gonads did not vary by type of shot. Kidneys and livers of Bi-dosed ducks had higher concentrations of Bi than in Pb- and Fe-dosed ducks. Muscle and blood showed no differences in Bi concentrations among doses. We found no histological dose-related effects in kidneys, liver, and gonads from the embedded shot.