Testis growth and regression in starlings (Sturnus vulgaris) as a function of the presence of females

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Abstract
Four groups of male starlings were exposed to stimulatory photoperiods. Two groups had 14 hours of light per day, the other two groups, 12 hours. One of the two groups treated with each photoperiod was in a cage including both male and female starlings; the other group was in a cage including only male starlings. Testis widths were measured via laporotomy every 15 days through a growth and regression cycle.Neither the rate of testis development, nor the maximum size reached, was significantly changed by the presence of the females in either photoperiod. Likewise, the chronology of testis involution in those treated with a 14 hour light per day photoperiod was not changed by the presence of females. But maintenance of spermatogenesis in birds treated with 12 hours of light daily was significantly longer in the group caged with females.