TABLE C-7.--Trend in waterfowl numbers, Central 
Flyway extended, winter survey, 1949-63 
[In thousands] 

Note.--Coverage during the period was not comparable 
and the data were adjusted, using 1959 and 1955 as base 
years. It was assumed that areas where comparable sur- 
veys were conducted provided an accurate measure of the 
percentage change between’2 consecutive years. On this 
basis, population estimates were calculated backward and 
forward from the base years. The 1962 figures are based 
upon only observed birds and are not adjusted. 
1 No surveys were conducted in Mexico in 1957. The 
data indicate that it is unlikely that surveys in the 
United States alone accurately revealed the trend in 
wintering population for either ducks or coot that year. 
2 Includes 111,718 miscellaneous unidentified birds. 
85 
