Determination of population distribution 
The density distribution of doves has been determined from a study 
of BDI values adjusted to a BY for each physiographic region and State. 
These data for 1971 have been assigned to one of five density classes. 
Changes in the adjusted BDI's greater than 10 percent between 1970 and 
1971 within physiographic region and State also were determined. 
FINDINGS 
From 1970 to 1971, the dove breeding population indexes decreased 
in each management unit; by 5 percent in the Eastern Unit, 4 percent 
in the Central Unit, and 2 percent in the Western Unit. All 1971 man- 
agement unit values are below the preceding 10-year means and are repre- 
sented by statistically significant downward population trends for the 
ll-year period, 1961-71. Further, all unit indexes are at their lowest 
levels for the 18-year period since establishment of the survey on a 
nationwide basis in 195). 
Status of the United States dove population 
1971 population dtstrtbuttion.--The density distribution of mourning 
dove populations in the United States is presented by State (fig. 3) and 
by physiographic region (fig. 4). The most extensive area of high dove 
density was in the middle States, especially in the eastern Great Plains, 
Central Lowlands, and in the lower Mississippi River plain. High densi- 
ties were also observed in the Upper Coastal Plain of Georgia and the 
Carolinas. A mean of 40 or more doves were heard per route in the States 
of Indiana, Kansas, and Nebraska (table 3). 

1970 to 1971 population changes.--The United States BDI declined 
3.7 percent from 18.7 doves heard per route in 1970 to 18.0 doves heard 
per route in 1971 (table 3). Changes greater than 10 percent in the BDI 
are illustrated by State (fig. 5) and by physiographic region (fig. 6). 
The 1971 indexes were generally lower than in 1970 in the southern two- 
thirds of the United States, and generally higher in the norther third. 
From 1970 to 1971, the combined hunting States index declined 5.7 per- 
cent, whereas the combined nonhunting States index increased 2.3 percent. 
LO 
