Incidence of lead shot in canvasbacks

During 1975 and 1976, 2,544 canvasbacks (Aythya valisineria) from North Dakota, Wisconsin, Illinois, and Maryland were flouroscoped to determine the incidence of body shot. A significant increase from west to east was detected in the incidence of shot for immatures from the four states. The incidence of shot in immatures after the 1975-76 hunting season was 18 percent in Maryland and 20 percent in Illinois. In Wisconsin no difference in the incidence of shot could be detected between areas trapped or time periods when trapping was conducted. In Maryland a significant decrease in the incidence of body shot was detected in adults, but not immatures, between 1975 and 1976. shot was located throughout the body of canvasbacks. Frequency varied from one to nine shot per bird and averaged 2.0 for adults and 1.5 for immatures.