. Bulletin. Natural history; Natural history. 268 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 decade, the incidence figure for Illinois mallards almost doubled. Increases in the percentage of water- fowl ingesting lead have paralleled in- creases in the number of waterfowl hunt- ers. Because there is expectation that the number of duck hunters will continue to increase, it can be anticipated that lead poisoning will become a greater hazard to waterfowl than it is at present. Incidence of Various Shot Levels. —The incidence of various levels of in- gested lead shot found among duck
. Bulletin. Natural history; Natural history. 268 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 decade, the incidence figure for Illinois mallards almost doubled. Increases in the percentage of water- fowl ingesting lead have paralleled in- creases in the number of waterfowl hunt- ers. Because there is expectation that the number of duck hunters will continue to increase, it can be anticipated that lead poisoning will become a greater hazard to waterfowl than it is at present. Incidence of Various Shot Levels. —The incidence of various levels of in- gested lead shot found among ducks of seven species in North America in the autumn and early winter months of 1938-1954 is shown in table 18 and fig. 6. (By level of ingested lead shot, or shot level, is meant the number of ingested shot pellets found in a gizzard.) The va- rious shot levels have an important bear- ing on the rate of mortality in ducks for, as will be shown later, the larger the num- ber of ingested shot pellets per duck, the higher is the death rate, other factors be- ing equal. Of 2,184 duck gizzards that contained lead when collected from hunters in many parts of North America in 1938-1954, per cent contained one pellet each, table 18; per cent contained two pellets each. Only per cent of the gizzards containing shot pellets contained more than six pellets each. Comparatively few ducks killed by North American hunters during the fall months in the period 1938-1954 carried 20 or more ingested shot pellets each, table 19. The maximum number of pellets re- corded was 172, in a lesser scaup gizzard. Cottam (1939:39) reported 1 to 58 pel- lets in individual gizzards of lesser scaups shot near Marquette, Wisconsin, in April, 1909; Shillinger & Cottam (1937:403) reported that 179 pellets were found in the gizzard of a pintail victim of lead poi- soning. Data in table 19 indicate that pintails, ring-necked ducks, and lesser scaup ducks are more likely to have large numbers of pe
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