SEX RATIOS 
The sex ratios among both immature and adult ducks of most of 
the species in the wing-collection samples are summarized in Table 53. 
The table shows the actual number of birds of each age and sex in the 
samples from each State, as well as both weighted and unweighted sex 
ratios for the Flyway as a whole. There were marked differences in 
the sex ratios of the various species. These differences will be 
discussed below under the species. 
Mallard 
Geographic differences in sex ratios of adult mallards are 
summarized in Table 54. Samples from most States contained more 
adult males than adult females. Females were slightly more numerous 
in the northern tier of Statese Numbers of immature males and females 
were much more nearly equale Only in Illinois did the sex ratio of 
immatures differ significantly from a 50:50 ratioe In Minnesota and 
Wisconsin a few more adult females than males were taken. In all 
other samples of adults, males predominated. The predominance of 
adult females in the samples from the northernmost States apparently 
resulted either from a greater vulnerability of females or from a 
greater availability in areas close to the breeding grounds. A 
predominance of females early in migration has been described for 
the black duck (Martin, 1960), and for the canvasback (Stewart, Geis 
and Evans, 1958, Geis 1959). The most unbalanced adult sex ratios 
were in the samples from Missouri, Illinois, Kentucky, Arkansas and 
Tennesseee Numbers of adult males and females were somewhat more 
nearly equal in the wing collections from Louisiana, Mississippi, and 
Alabama. Bag-check samples in Louisiana showed 91 males per 100 females 
in a sample of 212 adults (Smith, 1960), very similar to the proportion 
in the wing-collection samples. Sex ratios of adult mallards in the 
samples during the season are shown in Table 55. During the first 3 
weeks of the season, the sexes either were equal or there were slightly 
more females. During the remainder of the season, there were considerably 
more males than females. 
Changes in adult sex ratios also were examined in the data for 
the States (Table 56). In Minnesota, there were consistently more 
females until the last period(November 4-25) when the proportion of 
males increased, No seasonal change in sex ratios was apparent in 
either the Wisconsin or Michigan datas In the Iowa samples, adult 
females outnumbered adult males during the first week of the Season, 
but the proportions changed during the second period until there were 
slightly more males than females. During the latter part of the season, 
November 3 through December 8, there were more than two and one-half 
times as many males as females. The sample sizes were very small in 
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