The adjustment may be illustrated with data from Alabama 
where 1957 was selected as the base year (table 3). In that 
year the average number of doves heard calling per route was 
21.1. The percentage change in counts on comparable routes 
from 1957 to 1958 was an increase of 12.8 percent, so the 
base figure of 21.1 was adjusted upward by this percentage 
yielding an adjusted count of 23.8. In 1959, the percentage 
change from 1958 in counts on comparable routes was a decrease 
of 21.6 percent. The calculated 1958 "average heard" figure 
of 23.8 was, therefore, decreased 21.6 percent to provide the 
1959 figure of 18.7 doves per route. 
In 1965, base years were reselected for 21 States to 
coincide with the year in which each State first established 
and used random dove call-count routes. The adjusted number 
of doves heard calling and the resultant population indexes 
for each of these States were recalculated. The seven States 
in which random routes were run for the first time in 1965 
are slated for immediate reselection of base years and recal¬ 
culation of adjusted average number of doves heard as soon as 
the 1966 data become available. Thus, Western and Central 
Management Unit totals and percentage changes in 1966 will be 
based on routes all of which will have been randomly established. 
TRENDS IN THE BREEDING-POPULATION INDEX - 1965 
Eastern Management Unit 
The breeding-population index for the Eastern Unit decreased 
2.6 percent from the 1964 level (table 1). Although the popula¬ 
tion appears to be down, the index is only about 6 percent below 
the peak index of 1960 (figure 2). 
Hunting States showed essentially no decrease, but the index 
from nonhunting States was down 12 percent from 1964 (figure 3). 
The 1965 index for the whole unit is about 1.4 percent below 
the 10-year average index (1955-1964). 
Central Management Unit 
The Central Management Unit contains about half of the 
breeding habitat estimated to exist in the United States and 
about 55 percent of the nation's mourning dove breeding popula¬ 
tion. 
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