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differences in age ratios could have been due in some way to the 
differences in hunting practices in the three areas was pointed 
out by a number of refuge managers and by Mre Chattine Mre Re M 
Abney, Biologist at the Tule Lake Refuge, (letter of May 23, 1960) 
reported that the wings received from that area were collected 
"from birds bagged on refuge public hunting areas, where there 
was hunting every day of the season, and on a 'free lance' basis. 
In contrast, the Willows-Merced collections were probably made from 
State- opergted areas and private clubs where hunting management 
embodied ‘rest’ days, a limited number of hunters, and perhaps other 
controls. It is possible that these controls might function in such 
a way as to make the unwary immatures more vulnerable to the gun." 
Age ratios in samples of trapped birds suggest that different hunting 
conditions in the area are at best only a partial explanation. At 
Tule Lake, prior to the 1959 hunting season, the age ratio in trapped 
birds was 0035 immature per adult (Abney, letter of May 23, 1960) 
while at Merced it was 3.00 immature males per adult male and 2.78 
immature females per adult female (Chattin, letter of February 25, 
1960). These age ratios from trapped samples are almost exactly the 
same as those observed in the wing-collection samples from the same 
areas. This can be taken as evidence that the birds available in 
these areas prior to the hunting season had the same differences in 
age composition as later in the season. 
Mre Stroop, refuge manager of the Merced National Wildlife 
Management Area, offered another suggestion that might help explain 
the age composition of the wing collection in that area (letter of 
May 31, 1960). He suggested that locally produced birds could have 
concentrated in the areas at the time the wing-collection samples 
were gathered. He pointed out that the hunting area on Merced 
opened a month later than the general season, and that, therefore, 
birds produced locally could have been concentrated on the management 
area by hunting pressure on the outside. Table 37 shows that the 
age ratio in the hunting kill at Merced dropped substantially after 
the latter part of December, and so supports Stroop's hypothesis. 
This drop could have been produced, however, by the arrival of birds 
having lower age ratios. Despite the possible arrival of birds 
having low age ratios, age ratios among mallards in the Merced area 
were much higher throughout the season than those in wing-collection 
samples from areas farther north in California. 
Black Duck 
Regional differences in age ratios of black ducks are shown in 
Table 38. Age ratios declined progressively from north to south. 
The differences in the age ratios possibly reflect changes in 
vulnerability of immatures as the season progressed. Bednarik found 
2.21 immatures per adult in a sample of 241 black ducks shot at Magee 
Marsh in northeast Ohio. Although samples of black ducks in the 
wing collection were small, it was possible to divide the data from 
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