Standardized procedures were suggested for testing the call count 
so that the results could be subjected to statistical evaluation. Closed 
course routes of 20 stations at intervals of one mile to be censused in 
the early morning and early evening were suggested so that the resulting 
data from different latitudes could be compared intelligently. Weather, 
land use, and other factors affecting either the human ability to hear or 
the dove calling intensity were considered in order to permit evaluation 
of the effects of these factors in relation to the annual calling cycle. 
It was thought important that the resulting technique be broad enough in 
scope for use throughout the range of the Mourning Dove and permit area 
to area comparisons which could not be made through other indexing methods. — 
Marked similarities will be seen in the results of these intensive 
investigations from five areas in the eastern United States. During 1951 
the seasonal picture of Mourning Dove calling activity in different parts 
of the range was relatively uniform, usually with a pre-plateau peak in 
late April and early May which was followed by approximately a month of 
near=level calling activity. Data agree that from late April into July, 
calling levels are quite stable from station to station, indicating some 
degree of territorialism and no marked shifting of the calling population 
during this period. All data agree that the population is more homogeneous- 
ly spread throughout the range during this period than at any other season 
(cf. Nelson, 1951, Statistics as a Tool in Measuring Dove Inventories, 
8 pp., Mimeo. Oct.; Foote, Moore and Peters, 1951, Mourning Dove Newsletter, 
No. 4h, June 30, Summary Progress Report, Mourning Dove Study Report, 1952). 
Two studies indicate a relationship between calling birds censused and 
absolute numbers of calling birds, and one study calls attention to human 
variations in hearing and in interpreting numbers of birds calling. The 
data show a significant relationship (probably curvilinear) between calling 
rate and numbers of individuals calling. | 
These distinct similarities plus the statistical reliability of the 
data early suggested that an economical census index could be developed 
from these researches. Since the Cooperative Dove Investigation sought 
to secure management data as well as the necessary techniques, during 
1951 a total of 101 transects were sampled in various states east of 
the 100th meridian, statistically allowing designation of a 13 percent 
calling population change 95 percent of the time. Plans for the 1952 
counts, call for an increase to 176 transects to secure a better distribu- 
tion.of the sampling and (with the same variation) to allow prediction of 
a 10 percent calling population change 95 percent of the time. 
