POPULATION LOSSES IN THE MALLARD, 
BLACK DUCK, AND BLUE-WINGED TEAL 
Frank C. Bellrose 
and 
Elizabeth Brown Chase* 
Up to about 15 years ago, few wildlife conservation agencies had a significant amount 
of factual information on game populations and kill. Consequently most hunting regulations gov- 
erning the take of game were based largely on opinions and more often than not were applied in 
a hit-or-miss manner. Even though recent development of wildlife technology has given conser- 
vation agencies increasingly large amounts of factual information on which to base game regula- 
tions, most of the information obtained to the present time has been inadequate in that it has been 
concerned mainly with censuses of the population and inventories of the hunter take. 
POPULATION MECHANICS AND MANAGEMENT 
Officials engaged in drafting hunting regulations need to know more than trends in 
game populations and kill; they need to know the maximum proportion of a game population that 
can be harvested without adversely affecting the future of that population. It is evident that a 
large proportion of any game population will disappear each year from natural causes; itis a 
responsibility of management to see that the greatest possible use is made by man of the annual 
losses that normally occur. Shooting a wild duck in the autumn does not necessarily reduce the 
total spring population by one duck, for many a game bird falling before some hunter's gun would 
otherwise have died from natural causes before another breeding season rolled around. Para- 
phrased from Elton (1942): A duck shot might have died in any case the next day or week in its 
ordained place in the life curve. 
In order to formulate the proper hunting regulations for a game species, we must first 
measure the total annual loss that a population of that species undergoes, and we must measure 
the influence of varying kill intensities on that loss. What effect does a moderate hunter-kill have 
on the over-all annual mortality? How high can the kill rate go in a game species before it 
reaches a point beyond which the productivity potential cannot bring the population back to its 
former level? 
The year-to-year game-regulation "tactics'' should come, as they often do now, from 
up-to-the-minute census and kill information. The population information necessary to lay out 
the general game-regulation "strategy'’ should develop from long-term band recovery data and 
from age ratio data. Band recoveries furnish facts on population losses; age ratios supply facts 
on productivity. 
* Frank C. Bellrose, Associate Game Specialist, Illinois Natural History Survey; Dr. Eliza- 
beth Brown Chase, 1945-48, Research Assistant, Illinois Natural History Survey. 
