Following the tables comparing 1958 and 1959 data is a 
graph which presents the trend in duck, goose and coot population 
for the period 1949 through 1959. Survey coverage during the 
period has not been completely conparable. Therefore, the data 
have been adjusted to make them as comparable as possible. The 
adjustments were made by using 1955 and 1959 as base years and 
then assuming that areas where comparable surveys were conducted 
provided a measure of percent change from one year to the next. 
On this basis, population estimates were calculated backwards 
from the two base years. 
In some respects, it appears that the above method of 
adjusting data for comparability is not entirely adequate. For 
example, in 1957, it was not possible to conduct the annual winter 
survey in Mexico and the trend figure for 1957 was calculated on 
the basis of changes in population observed in the United States 
only. It does not seem likely that the marked reduction in the 
duck and coot population recorded in the Central Flyway States in 
1957 properly reflected the trend in populations wintering in the 
Flyway. 
Generally speaking, the trend in wintering populations 
of ducks in the Central Flyway seem to have been slightly upward 
during the ll-year period, the trend in goose population seems to 
have been somewhat downward, while the data for coot seems to show 
that the population has fluctuated markedly. For coot the informa- 
tion may be of questionable value for the purpose of determining — 
population trend. 
Percent Change in Central Flyway Population Index Figures 
for Ducks, Geese, and Coot - max x ve to eae 1999 
Comparable Coverage ) 


Area Ducks Geese Coot Total 

Central Flyway 

States - 18 4) Boe” = ao: - 18 
Mexico ~- Central f 9k f 188 f 293 f 107 
Mexico - East Coast - 21 pf Ble te Be eer SEL! 
TOTAL _ ae . BR * ae ~ 42 

