Abstract
Day length regulates the circadian behavior of several avian species. The birds can synchronize their circadian behavior with photoperiod length and different levels of illumination. The present study investigated the effects of pre-exposure to long and short photoperiods on nighttime activity behavior (Zugunruhe) in redheaded buntings. The analysis of locomotor activity data was conducted across both long and short photoperiods. The experiment was completed in two phases. In phase I, two groups of birds were exposed to 13L:11D and 11L:13D (group 1) and 8L:16D (group 2) photoperiodic conditions for 30 days. Then, all birds from both groups were transferred to a short photoperiod (8L:16D) for the next 28 consecutive days in phase II. Data on locomotor activity were presented as actograms, a daily activity profile (24 h), and total activity counts (day/night). Clearly, birds change their locomotor activity patterns in response to different photoperiods under a LD cycle. Birds of both groups were active during the day under 13L, 11L (phase I), and 8L photoperiods (phase I & II). Most locomotor activity in all birds was concentrated during the light phase. Interestingly, the birds showed migratory restlessness behavior (Zugunruhe) under an 8L:16D photoperiod, which received pre-exposure to 13h of light during phase I. But no nighttime locomotor activity was observed in birds exposed to a short photoperiod (8L:16D) throughout the experiment. The present study demonstrated that the onset of night migratory behaviour (Zugunruhe) depended on pre-exposure to a stimulatory photoperiod.
Get full access to this article
View all access options for this article.