Environmental enrichment can have effects on the physiology and behavior of animals. In our study we addressed the effects of physical enrichment on the activity behavior of a subtropical songbird, the Spotted Munia (Lonchura punctulata). Specifically, we measured the activity-rest pattern in two groups of singly housed Spotted Munia (N = 6 each), with or without alterations in cage environment, in both the rhythmic (synchronized) and arrhythmic states. Birds were sequentially exposed to a 12/12-h light/dark (12L/12D) photoperiod (synchronized, rhythmic state) and to constant bright light (LL; arrhythmic state; bright LL causes disruption of circadian rhythmicity) for 6 and 2 weeks, respectively. Group 1 birds' cages were enriched with green grass nest cups and green twig foliate perches, which altered the complexity of the caged envi- ronment, representing the enriched environment (EE). Group 2 birds' cages remained as before; representing the non-enriched environment (NE). Birds on 12L exhibited a bimodal diurnal activity pattern with similar activity levels regardless of their cage environment. In comparison, birds in the EE exhibited a significantly smaller phase difference between light and activity onsets and, therefore, showed a shorter activity duration than those housed in the NE. Further, in the first week of LL, both EE and NE birds exhibited a similar response, with half of birds in each group in circadian rhythmic and arrhythmic states. In the second week of LL, all birds showed circadian arrhythmia, but more birds in the EE than in the NE had rhythmic activity bouts, with four of six EE birds and one of six NE birds being in ultradian rhythm. Thus, physical enrichment of the cage environment influenced the pattern, phase and duration of activity behavior in the Spotted Munia. We suggest that the physical environment actively contributes to the optimization of circadian clock controlled behavior in animals.