MONTHLY WILDLIFE RESEARCH LETTER 
Department of Conservation and Natural History Survey, Cooperating 
T. G. Scott, Editor 
Urbana, Illinois 
June, 1961 
Vol, U, No. 6 
W-30-R-1U 
R. F. Labisky, S. H. Mann 
The crowing of cock pheasants on the Sibley area reached maximum frequency 
between May U and 7 in each of the five years, 1957 through 1961. This precise 
timing of maximum crowing occurred in spite of variations in weather conditions 
in these years. Such precision suggests a constant control mechanism. Weather 
factors, such as precipitation, temperature, or sunlight, would not provide such 
constancy. It would appear that photoperiod, and not light intensity per se , 
must be involved in the regulation of crowing by cocks. This is to say that 
increasing photoperiod associated with increasing day length or the decreasing 
ratio of dark to light may reach an "optimum" at which time maximum crowing occurs 0 
It is possible that the photoperiod stimulus acts neurohumorally through the 
hypothalamus to release gonadotropic hormones (GTH) necessary for testicular 
recrudescence and subsequent production of androgen, which is ultimately responsible 
for crowing. Some aspect of increasing photoperiod may reach a critical level after 
early May (for the Sibley area) and would then tend to act as a depressor, in¬ 
hibiting the release of GTH. However, until refined crowing-count data become 
available for areas with latitudes different than that of Sibley it will be 
impossible to ascertain the role of the photoperiod in regulating the crowing of 
cock pheasants. 
Should the photoperiod factor be responsible in regulating crowing of cocks, 
it would become feasible to predict the peaks of crowing by cocks on different 
areas (by computation of the photoperiods at different latitudes). If the period 
of maximum frequency of crowing could be determined for each area, much less time 
and money would be expended by biologists in obtaining reliable call counts of 
pheasants each spring. 
W-H2-R-10 
R. D. Lord, Jr., D. A. Casteel 
The nest attendance records taken automatically on two cottontail nests in 
our enclosure showed that each female spent most of the first night following the 
night of birth at the nest, presumably nursing their young. Then neither rabbit 
natural 
