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Ducks; Birds--Migration; Bird populations; Fowling


The incidence of lead shot in l ,687 lesser scaup (Athya affinis) and 416 ring-necked ducks (Athya collaris) in spring migration in Minnesota and the implications as related to the bird population and hunting harvest the preceding fall are considered in this study. The ducks, which were examined for shot by photofluorographic radiography had died as a result of oil pollution on the Mississippi River in the vicinity of Red Wing in the spring of 1963. The birds were separated into two age groups and by sex. Yearling lesser scaup had a body shat incidence (proportion of birds containing shot) of 5.5 per cent and yearling ring-necked ducks 17.8 per cent. For both species, yearling males had a higher incidence of shot than yearling females, and the most common location of shot was just beneath the skin on the back and abdomen. By using shot incidence in conjunction with other data, the harvest rate during the preceding hunting season (1962) was estimated as being 15 to 20 per cent of the population for yearling lesser scaup of both sexes; 30 to 35 per cent far yearling female ring-necked ducks, 60 to 70 per cent for yearling males, and 45 to 55 per cent for yearlings of both sexes of ring-necked ducks combined. Incidence of ingested shot in the digestive tracts of the birds (mostly gizzard) was low, being 1.7 per cent for lesser scaup and 1.6 per cent far ring-necked ducks.

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