




























1970 to 1971 population changes.--The Eastern Unit BDI declined 
h.8 percent from 18.8 doves heard per route in 1970 to 17.9 doves 
heard per route in 1971 (table 3). The 1971 population levels were 
generally higher than in 1970 in areas bordering the Great Lakes, 
north Atlantic Coast, and southern Mississippi River. Population 
indexes were lower in the central and southeastern sections of the 
Unit (figs. 5, 6). From 1970 to 1971, the combined hunting States 
index decreased 10.9 percent and the combined nonhunting States index 
increased 11.4 percent (table 3). 
Mean temperatures at the start of the survey were significantly 
colder in 1971 than in 1970 by 4.2 degrees Fahrenheit for the Eastern 
Unit, 3.2 degrees for the hunting States, and 6.6 degrees for the non- 
hunting States (table 2). No appreciable change occurred between mean 
Survey dates or percentage of high disturbance recorded per route in 
1970 and 1971. 
1961 to 1971 long-term populatton trends.--In 1971, the Eastern 
Unit BDI declined to its lowest level for the ll-year period (table 3, 
fig. 7). The indexes have declined during 4 of the last 5 survey years. 
opulations for the combined hunting States were also at their lowest 
levels in 1971 following 5 years of decline during the last 6 years 
(table 3, fig. 12). In contrast, the combined nonhunting States index 
has increased for the third successive year to its highest level in 11 
years (table 3, fig. 12). The adjusted Unit BDI for 1971 is 6.7 per- 
ent below the preceding 10-year mean (fig. 7). The combined hunting 
States index is 16.0 percent below the 1961 average, and the index for 
the combined nonhunting States 20.4 percent above this mean (fig. 12). 
Regression analysis shows a significant downward trend in the 
Eastern Unit population between 1961 and 1971; the mean rate of decline 
was determined to be 1.0 percent per year (table 3, fig. 9). During 
the same period, the combined hunting States declined significantly at 
an average annual rate of 2.0 percent, whereas the nonhunting States 
increased significantly at 2.1 percent per year. The nonhunting States 
in the Eastern Unit represent the only grouping of States having an 
upward population trend. Significant upward population trends occurred 
in Indiana, Maryland, Ohio, and Rhode Island; downward trends were 
determined for Florida, Louisiana, Maine, New York, Wisconsin, and 
West Virginia (table 3, fig. 10). 
el 
