It was observed while taking the absolute census that in the spring 
and early summer doves have long periods of continuous calling but in the 
late summer many doves will call for periods of a few seconds only and 
then remain quiet for long periods. There were some mornings in August 
on which no calls at all were heard during the absolute census. However, 
the very next morning might be marked by a period of intense calling in 
the very same area. This habit of sporadic calling in August makes it 
more difficult to take an absolute census as the doves may stop calling 
before they can be located. Often it was necessary to remain in the 
same spot for an hour waiting for one of these spells of sporadic calling. 
Discussion 
A comparison of the one-man call count and the five~-crew count over 
all twenty stations (Figures 8, 9, 10) does not show a very close agree-~ 
ment in the average number of doves heard. Generally speaking the five- 
crew count and the one-man count agree on the scarcity and abundance of 
doves at most of the stations. The five crews heard, on the average, 
more doves than the writer in every count that was made (Table 1). 
Table 1.--Average number of doves heard by one-man call count 
an, ve two-man crew count by months 

A.M. P.M. 

One-Man Five-Crew One-Man Five-Crew 
April 11.33 28.77 6.00 16.10 
May 15.00 -- 10.33 Ae. 
June 14.00 27.62 8.50 13.87 
July 12.00 ~~ 5.00 as 
August 11.33 15.50 3.00 3.10 

The evidence shows that the writer, who ran the one-man call count, 
was well below the average in the perception of dove calls (Figures 8, 9, 
10). This inability of the writer may explain why there is a lack of high 
counts at stations like number 8 in June where there were surely doves to 
be heard aS an examination of the five crew count will show. This lack of 
acuity of hearing may also explain the blank stations on the route-stations 
where experienced men in the five two-man crew heard doves consistently. 
How can it be explained that the five crews were hearing twice as 
many doves in April and June as the writer whereas in August they were 
hearing approximately the same number (Table 1, Figures 8, 9, and 10)? 
When the doves are numerous or the calling is intense as in April and 
June the person of low perception finds the doves difficult to separate 
and may report too few in an effort to keep from over estimating their 
number. On the other hand when calling is less intense, or is sporadic 
as in August the person of low perception may be able to count them more 
easily. 
