Status of the Western Management Unit population 













1971 populatton distrtbutton.--Highest population densities in the 
Western Management Unit were essentially restricted to coastal Californj; 
and sections of the Columbia Plateau. Lowest densities were distributeg 
through much of the Great Basin and the northwestern part of the Unit 
(fig. 4). Idaho had the highest adjusted BDI of any Western Unit State 
in 1971, with 23.2 doves heard calling per route (table 3, fig. 3). 
1970 to 1971 population changes .--The Western Unit BDI declined 1.6 
percent from 12.4 doves heard per route in 1970 to 12.2 doves heard per 
route in 1971 (table 3). Populations increased in several regions, 
especially in the States of Oregon and Utah (figs. 5, 6). Substantial 
population declines were evident in much of Arizona and Nevada. All 
States within the Western Unit hunt mourning doves. 
From 1970 to 1971, the mean temperature at the start of the surveys 
declined by 3.4 degrees Fahrenheit for the Western Unit (table 2). The 
average survey was run one day later in 1971 than in 1970. The 1971 
survey routes were run under conditions of slightly greater high disturba, 
1961 to 1971 population trends.--The 1971 BDI for the Western Unit 
is the lowest observed for the ll-year period (table 3). This is the 
seventh successive year without an increase in the population index. 
1971 index is 24.8 percent below the preceding 10-year mean (fig. 7), 
represents the greatest departure of any management unit. 
Regression analysis shows a significant downward trend in the dove 
population index from 1961 to 1971. The BDI declined at an average a 
rate of 4.4 percent along the calculated regression line--the greatest 
rate of decline of any management unit (table 3, fig. 9). Between 1961 
and 1971, only the State of Nevada had a significant upward population 
trend. Significant downward trends occurred in Arizona, California, and 
Oregon during the same period (table 3, fig. 10). 
Statistical significance of data 
1970 to 1971 population changes.--No significant (p<0.05) changes 
occurred in the BDI's of any management unit (table 1). Within the Fast 
ern Management Unit, the BDI for the combined hunting States declined 
between 1970 and 1971 (p<0.01). None of the indexes for the other com- 
bined hunting States or combined nonhunting States were significantly ~ 
different between these years. Although not designed to detect popula- 
tion changes within States, the survey showed significant increases in 
Indiana, Michigan, Wisconsin, and Utah. Significant decreases occurred 
in Florida and Arizona (table 1). 
eh 
