Hormonal correlates of gonadal regression and spontaneous recovery in Japanese quail exposed to short day-lengths.

Adult male Japanese quail were transferred from long to short days. Plasma testosterone and dihydrotestosterone quickly decreased and this endocrine response was followed by a regression of the cloacal gland, an androgen-target organ. After about a month, a spontaneous recovery of gonadal activity was observed in some but not all birds. It was not associated with obvious shifts in the circadian system. The physiological bases of this spontaneous recovery are discussed as well as the detailed relationships between plasma testosterone and cloacal gland size.