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 have been applied to the base figure 
(average doves heard calling per route) to give an adjusted 
figure 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. From a base year, average 
doves heard calling per route for each State has been adjusted 
annually according to the percentage change from the preceding 
year in counts on routes covered both years. For example, 
1957 was selected as a base year in Alabama (table 2). In 
that year, the average doves heard calling per route was 21.1. 
In 1958, the percentage change from 1957 in counts on comparable 
routes was an increase of 12.8 percent, so the base figure of 
21.1 was adjusted upward by 12.8 percent to a level of 23.8. 
In 1959, the percentage change from 1958 in counts on comparable 
routes was a decrease of 21.6 percent, so the 1958 adjusted 
figure or adjusted base was decreased by 21.6 percent, from 
23.8 to 18.7. 
TRENDS IN THE BREEDING POPULATION INDEX - 1962 
Eastern Management Unit 
The breeding population index for the EBastern Unit decreased 
3 percent from the 1961 level (table 1). Figure 2 shows that 
the breeding index of the Eastern Unit increased generally over 
the 7-year period prior to 1961, followed by a 2-year decline. 
“ee In hunting States of the Eastern Unit, the breeding index 
remained unchanged from 1961. In nonhunting States, the index 
decreased 12 percent: from 1961 to 1962 (table 1). The long-term 
trend of the breeding index in nonhunting States of the Eastern 
Unit is shown in figure 3 and indicates a relatively stable 
population in recent years. 
Central Management Unit 
The breeding population index for the Central Unit decreased 
11.5 percent from the 1961 level (table 1). Figure 2 shows that 
for 6 years up to 1960 the breeding index of the Central Unit 
generally increased. This has been followed by declines in 
1961 and 1962. 
