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| Extended nighttime leads to dawn chorus-like intense singing in adult zebra finches. |
| Satoshi Kojima1, Chihiro Mori2, Joowon Kim1, Ednei B. dos Santos1. 1Korea Brain Research Institute, Daegu, , South Korea; 2Teikyo University, Tokyo, Tokyo, Japan |
Birds have served as important models for understanding how animals adjust their behavioral rhythms to variations in day/night length. Using captive zebra finches, we tested if nighttime length affects singing behavior in the subsequent morning. We conducted an experiment manipulating nighttime length in sound-proof boxes by shifting light-on time in the morning to observe the potential impact of 'short' vs. 'long nights' on singing motivation. Then, we manipulated nighttime length again allowing a gradual transition from dim light to full brightness. Also, we explored the role of melatonin in singing motivation, conducting a systemic injection experiment using Luzindole, a selective antagonist of melatonin MT1/MT2 receptors. Our results show that: longer nights lead to increased singing rates and shorter latencies to start singing; birds initiate singing under dimmer light conditions following longer nights compared to shorter nights; and birds start singing earlier when they receive Luzindole injections. These results suggest that extended night periods suppress singing and boost singing motivation, leading to intense singing early in the morning, reminiscent of a dawn chorus. |