Effects of nontoxic shot regulations on lead accumulation in ducks and American woodcock in Canada.

Prior to the first nontoxic shot zones being established in Canada, a nationwide survey of lead (Pb) concentrations in wing bones of hatch year (HY) dabbling and diving ducks determined the incidence of elevated Pb exposure in waterfowl in different parts of the country (Scheuhammer and Dickson 1996). The main objectives of the present study were (1) to compare these previously collected data with the incidence of elevated Pb accumulation in the same species several years after the establishment of a national regulation in 1997 prohibiting the use of Pb shot for waterfowl hunting; and (2) to survey waterfowl hunters to determine reported levels of compliance with the nontoxic shot regulation. Average bone-Pb concentrations in dabbling ducks (mallards [Anas platyrhyncos] and American black ducks [Anas rubripes] combined) decreased significantly between 1989+1990 and 2000 (11 microg/g vs. 4.8 microg/g, respectively [p < 0.01]). Ring-necked ducks (Aythya collaris) showed a similar decrease in mean bone-Pb concentrations, from 28 microg/g to 10 microg/g (p < 0.01). These declines in bone-Pb concentration were consistent with the results of a large anonymous hunter survey, which indicated a high level of reported compliance (>80%) with the nontoxic shot regulation among waterfowl hunters residing in Ontario and British Columbia. Conversely, American woodcock (Scolopax minor), an important upland game species not affected by the nontoxic shot regulation, showed no decrease in mean bone-Pb concentration since the national regulation came into effect (19 microg/g in 1995 vs. 21 microg/g in 2000). A majority (70%) of waterfowl hunters in British Columbia and Ontario who also hunt upland game birds report continued (legal) use of Pb shot for upland game bird hunting.