
Analyses of several factors associated with these surveys show 
that the mean temperature at the start of the 1971 survey was signif- 
icantly colder than in 1970: United States, - 3.6 degrees Fahrenheit; 
hunting States, - 3.2 degrees; and nonhunting States, - 4.8 degrees 
(table 2). In 1971, the surveys were run an average of one day earlier 
than in 1970. The percentage of survey stops with audible disturbance 
great enough to seriously affect the counting of calling doves.increased 
from 7.9 percent in 1970 to 8.7 percent in 1971. 
1961 to 1971 long-term population trends .--The 1971 BDI's adjusted 
to a Base Year for the United States and the combined hunting States 
are the lowest observed for the ll-year period, 1961-1971 (table 3). 
This represents the fifth successive year without an increase in the 
population index. In contrast, the adjusted BDI for nonhunting States 
increased for the first time in 1971 following 4 successive years of 
decline. The indexes for these areas in 1971 are well below the pre- 
ceding 10-year means: United States, -14.4 percent; hunting States, 
-14.4 percent; and nonhunting States, -14.7 percent. 
Adjusted BDI's plotted in figures 7 and 8 reflect the general 
downward trend in population indexes since 1961. Linear regression 
analyses of these data (table 3) are shown in figure 9. The indexes 
declined at an average annual rate of 2.5 in the United States, 2.3 
in the hunting States, and 2.9 percent in the nonhunting States. This 
study reveals a significant overall decline in nationwide dove breeding 
populations between 1961 and 1971. 
eae 
Population trends as determined from linear regression analyses 
are shown by State (table 3, fig. 10) and by physiographic region 
(table 4, fig. 11). From 1961 to 1971, statistically significant down- 
ward trends exist in much of the northern Great Plains and the Pacific 
border and southern border States. Trends are significantly upward in 
several scattered mid-latitude States. 
Status of the Eastern Management Unit population 
1971 population distrtbutton.--Highest dove population densities 
in the Eastern Unit were in the west-central section, especially in 
the Central Lowlands, and in portions of the Upper Coastal Plain and 
Mississippi Alluvial Plain. Densities were generally low in the 
Appalachian Highlands, northern uplands, and the lower Atlantic Coastal 
Plain (fig. 4). States represented by a mean of 30 or more doves heard 
er route included Indiana, New Jersey, Mississippi, and Tennessee 
maple 3, fig. 3). 
15 
