— — ee rN TE. re, 
2e Chronological variation 
Seasonal changes in mallard age ratios are shown in Table 34 
for the entire Flyway. Age ratios dropped markedly during the 
first three weeks of the season, then from November through the 
end of the season continued to be less than one immature per adult. 
The drop in age ratios as the season progressed apparently was due 
to an increase in the portion of the kill occurring in the southern 
States, where mallards had low age ratios throughout the season. 
Changes in the relative vulnerability of the two age groups probably 
also contributed to the drop. Inspection of the weekly data indicated 
that weighting of the State data would have little effect on the 
estimates for the entire Flywaye In most States, age ratios for a 
given week either were similar to each other or, if they were dis- 
similar, the State had its proper weight. Data from Minnesota, 
Iowa,and Ohio were exceptions, so the observed data for those States 
were weighted as described earlier before obtaining the weighted totals. 
Seasonal changes in mallard age ratios in certain States of the 
Mississippi Flyway are summarized in Table 35. The States included 
are those having large enough samples to make the comparisons mean- 
ingful. Age ratios on opening day are shown also for those States 
having the largest samples. 
The age ratio in Minnesota on opening day was 1.91 immatures 
per adult, but during the remainder of the first week the average 
age ratio was 1.11 immatures per adult. This change may have been 
due to a greater vulnerability of immatures on opening day. During 
the remainder of the season, age ratios were lower but showed no 
consistent trende 
In Wisconsin, on opening day, a sample of 30 birds had an age 
ratio of 5.0 immatures per adult. The age ratio during the remainder 
of the first week of the season was 2.52e During the period of 
October 14 through October 27, the age ratio dropped to 1.42, and 
during the remainder of the season, October 28 through November 25, 
the age ratio was 1.89 immatures per adult. 
In Michigan, age ratios decreased from 4.54 during the first 
four days of the season to 2.38 during October 12 through 25, then 
to 1.06 immatures per adult during the remainder of the seasono 
Age ratios in the first week of the season in Iowa were extremely 
low, averaging 9.28 immature per adult. Age ratios increased pro- 
gressively thereafter to 0.45 during the period of October 27 to 
November 2 and to 1.00 for the remainder of the season (November 3 
through December 8). The increase in age ratios during the period 
Novenber 3 through December 8 probably was due to the arrival of 
~23- 
