The formula for deriving the corrected number of recoveries for the O-1 year-class 
to the end of the banding period is as follows: 
Corrected number of 
recoveries from Octo- Number of days from 
ber 1 to end of banding October 1 to end of 
period = banding period 
Actual number of re- Number of days from 
coveries before end of mean banding date to end 
banding period of banding period 
Recoveries from the time banding is terminated until September 1 of the following 
year are added to the corrected number of bands recovered up to the end of the banding period. 
The result gives the corrected year-of-banding recovery data, which are roughly comparable 
to recovery data for ducks banded on the breeding grounds before the beginning of the hunting 
season. 
Below is given an example of the use of the formula in correcting the year-of-band- 
ing recovery data. Bands were recovered from 33 juvenile male mallards during the 1939 
banding period and 16 after the end of this period but before the following September 1 -- a total 
of 49 recoveries, table 1. The number of days from October 1 to termination of banding in 1939 
was 89. The number of days from mean banding date to end of the banding period was 28.2. 
Substituting the appropriate figures in the formula gives the following equation: 
x = 89 
33 28.2 
a = 89 x 33 
28.2 
x = 104 
To 104, the corrected number of band recoveries before the end of the banding period, 
are added the 16 recoveries after the end of this period, to give a total of 120, table 1. 
Another method by which the corrected number of recoveries can be determined is 
more nearly accurate for individual years, but it requires a good sample of recoveries for a 
given year from prior bandings; it cannot be used for the year in which banding is first instituted! 
This formula is as follows: 
Corrected number of Total number of previously 
recoveries from selected banded ducks recovered in 
year of banding — selected year 
Actual number of recoveries Number of previously banded 
from selected year of band- ducks recovered after mean 
ing before end of banding selected-year banding date 
period before end of banding period 
In addition to these two formulas developed by the authors for correcting current- 
year banding data on the flyways is still a third method, which was developed simultaneously 
and independently by Thompson & Jedlicka (1948). 
Year-of-banding band recoveries for the blue-winged teal, table 7, were not corrected 
