Effect of no-night light environment on behaviour, learning performance and personality in zebra finches

- We examine behaviour, learning and cognition in zebra finches under constant light, LL.
- Separate clocks seem to control the timing of daily activity and singing patterns.
- Prolonged LL restores daily rhythms in activity and singing in most zebra finches.
- LL induces a decrease in learning and cognitive performance.
- LL negatively impacts personality, measured with respect to an exploratory trait.

A periodic day-night environment is critical for daily behavioural patterns and advanced brain functions such as learning and cognition in animals. We investigated whether a no-night light environment would impair these functions in parent and F1 and F2 zebra finches, Taeniopygia guttata. Particularly, we examined song acquisition as a measure of learning, tested cognitive performance with reference to spatial and colour association tasks, and assessed personality with respect to an exploratory trait, first in the parent (P) and subsequently in F1 and F2 birds born and raised under 12:12 h light:dark or constant light (hence no-night, LL) environments. Daily patterns in activity and singing were monitored as circadian response indicators. After initial decay, the rhythmic patterns in daily activity and singing were restored after several weeks in the majority of P and F1 birds under LL; F2 birds displayed robust circadian rhythms in both behavioural patterns under LL. Further, LL decreased participation and performance in cognitive tests and reduced exploratory behaviour in birds from all generations. Overall, we found negative effects of the LL environment on daily behavioural patterns, advanced brain functions (i.e. learning and cognition) and personality in zebra finches when adult and in subsequent generations. These results give insights into the possible impact on animals of night-time illumination such as in an overly lit urban habitat.