Ge 
Table 6.--Weights of mallards taken in the Tillinois Valley, 
1938. 
Number Weighed Average Weights* 
Period Drakes Hens Drakes!” ‘Hens | 
October 15-31 er 82 43.8 56.8 
November 1-15 68 69 AN. 9 Oho 
November 16-28 196 | meee peel Seared 
Total O41 269 42.8 O72 
“Weights in ounces 
The fact that the weights of females increased as the sea- 
Son advanced whereas those of the males behaved erratically seems to 
be further evidence that the male migration is more or less independ- 
Eat Of that of the female. 
LO. Age groups: The goal of game management Is the ethical 
mervesting of the surplus. A surplus in that part of a population in 
excess of a breeding stock large enough to maintain the species at 
pome desired population level. In waterfowl at the present time, 
mors is no surplus, because the desired population level Is.not in 
meeot. Wwe are, therefore, harvesting a portion of the capital stock. 
Bithough this is not good management, under the circumstances, it is 
Boe best thing to do. It means, however, that unusual vigilance must 
me Girected toward the status of the capital stock, to guard against 
Bnarp deflation. 
Since increases or decreases in the duck population are 
Meamarily the- result of successes or failures in breeding, it seems 
Jogical that actual measures--not guesswork--are necessary in deter- 
Mining the number of young ducks raised. Two methods of measuring 
the number of young birds in relation to the number of old birds 
meme bo hold the best possibilities: (1) inspection of the kill of 
Hunters (2) banding. both mcthods are limited in application because 
Mm 8 dearth of definite and usable criteria in some species for sep- 
Meeting birds of the year from thoir parents. Work is now in progress 
GO remove this obstacle. 
1939 ACTIVITIES AND FINDINGS 
In addition to wood duck nesting studies (to be reported 
in another paper) the 1939 waterfowl program of the Illinois Natural 
History Survey has given major consideration, up to September 20, to 
meeuck food survey of the Illinois Valley. This is a continuation of 
Studics started in 1938. 
