Constant light and removal of the pineal gland disturb daily singing patterns and reduce breeding success in zebra finches

A significant increase in body mass and testis size was observed in male zebra finches exposed to constant light.

• Testis size decreased under constant darkness conditions.
• Singing patterns were synchronized with the light phase under a 12L:12D schedule but became arrhythmic under constant light.
• Pinealectomy disrupted both activity and singing rhythms, but did not alter the overall features of the songs.
• Pinealectomized pairs showed a notable reduction in nest-building and breeding efforts.
• The findings indicate a potential role of the circadian clock in regulating singing and reproductive behaviors in zebra finches.

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