The Role of Darkness in Sexual Activity of the Quail

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Abstract
Under natural conditions in the bobwhite quail (Colinus virginianus) the period increase in genital physiology, culminating in reproduction, corresponds with the period of increasing daylength in the spring. Experimentally, the same conditions can be duplicated in midwinter under artifical illumination of 17 hrs. per day, and conversely the typical spring-time changes will not appear under exp. short-day conditions. However, midwinter birds showed full sexual activity (after 37 days) on an exp. 9-hr. day when the dark period was interrupted each night with one hour''s illumination. Male birds on a 10-hr. day, with only 15-min. of light during the night also come into full sexual activity. Thus both the light period and the dark period are important in the changing pattern of genital physiology.