BIRD BANDING LINCOLN 



335 



Table 3. — Percentages of returns throughout the country of banded ducks during 

 the shooting season immcdiatelij follotoing their tanding, 1920-1926 



Table 3 shows this relationship and the percentages based on the 

 material available after seven years' work. The average of about 

 12 per cent is slightly increased when the results from the different 

 banding stations are considered separately, the average first-season 

 recoveries being between 12 and 13 per cent. Twelve per cent, how- 

 ever, is very close to a general average and may be accepted as a 

 basis for computation, particularly when it is remembered that we 

 are dealing with a problem in which the units are to be shown in 

 millions. Disregarding other factors (which are, however, of de- 

 cided importance), an illustrative case may be assumed as follows: 

 If in one season, 5,000 ducks are banded and these yield the expected 

 GOO first-season returns, or 12 per cent, and during that same season, 

 the total kill is determined at 5,000,000, then the waterfowl popula- 

 tion for that reason was approximately 42,000,000. To assume 

 further : If during the following season (both seasons of equal 

 length), the total kill is estimated at 500,000 birds less, then the 

 total duck population for that year would be about 37,500,000, or 

 an approximate decrease of 4,500,000 in the continental waterfowl 

 population. 



Such figures naturally should be considered only as approxima- 

 tions but they would at least have the merit of being based on 

 factors ai^pearing to have a definite relationship. As the work 

 continues, additional data are being accumulated so it should be 

 possible ultimately to arrive at an average percentage in which the 

 margin of error will be reduced to a negligible quantity. 



Sex ratio. — It is common knowledge among sportsmen that the 

 average bag of ducks is likely to contain more males than females. 

 This, however, is not surprising, since it is fairly obvious that in a 

 mixed flock of both sexes the aim of tlie shooter would unconsciously 

 be directed toward the males because of their more striking and con- 

 spicuous plumage. 



But it would seem that the large cage traps used to capture ducks 

 for banding can not be selective as regards sex. As a matter of fact, 

 observations of the autiior on one species, the pintail, indicate the 



