
Long-term Trends 
For the purpose of showing long-term trends in the 
breeding-population index of a State, a base year was selected, 
and annual percentage changes are applied to the base figure 
(average doves heard calling per route) to give an adjusted base 
which shows the true relation of indexes from year to year. The 
selection of a base figure is necessary because not all routes 
are censused each year. To measure year to year changes in indexes, 
only routes censused in both years are used. For example, in table 1 
the adjusted base figure for Alabama in 1959 is 18.7 doves heard 
calling per route. To adjust this base figure to its proper 1960 
level, the percentage change in doves heard calling on comparable 
routes in 1959 and 1960 is applied to the 1959 base figure. The 
percentage change in Alabama was an increase of 21.2 percent, 
which increases the base figure from 18.7 to 22.7. 
TRENDS IN THE BREEDING-POPULATION INDEX - 1960 
Eastern Management Unit (figure 1) 
The breeding-population index for the Eastern Unit in- 
creased 5 percent fram the 1959 level (table 1). Figure 2 shows 
that the breeding index of the Eastern Unit has been increasing 
rather steadily over a 7-year period and is now 38 percent above 
the 1953 level. 
In hunting States of the Eastern Unit, the breeding index 
increased 5 percent above the 1959 index and is 45 percent above the 
1953 level (table 1 and figure 3). In nonhunting States, the 1959 
to 1960 trend was up 3 percent (table 1). The long term breeding= 
index trend in nonhunting States of the Eastern Unit is shown in 
figure 3 and indicates a relatively stable population in recent years. 
The 1960 index, however, is 21 percent above 1953. 
Central Management Unit (figure 1) 
The breeding-population index for the Central Unit in- 
creased 14 percent from the 1959 level (table 1). Figure 2 shows 
that for six years during a 7-year span the breeding index of the 
Central Unit has increased and is now 69 percent above the 1953 level. 
