RESUMEN
To test the circadian clock characteristics, activity behaviour of male blackheaded munia was recorded. Two experiments were performed. In experiment 1A, activity of munia was recorded under long days, LD (14L: 10D); and short days, SD (10L: 14D). Locomotor activity of two groups of munia exposed to equinox (12L: 12D) daylength followed by transfer of one group each to continuous dimlight (DD) and continuous bright light (LL) was recorded in experiment 1B. Experiment 2 aimed to describe seasonal trend in daily pattern of activity/rest cycle under natural illumination conditions (NDL). Hourly activity during daytime was more under SD than under LD. Munia did not exhibit bimodality in daily activity pattern; activity during morning, M (2h) was more than evening, E. A free-running activity rhythm was recorded in munia under DD; the same was arrhythmic under LL. The seasonal pattern in daily activity profiles under NDL corresponds to the seasonal changes in daylength. Daylength regulates daily and seasonal activity patterns in blackheaded munia.