Figure 1.

A) Experimental protocol. Photosensitive black-headed buntings maintained on short days (SDs; 8 h light:16 h darkness, pretreatment) were divided in 3 groups and singly housed in activity recording cages. Group 1 was retained on SD throughout the 24 d treatment period (SD-S), while groups 2 and 3 were exposed first to SDs and then to long days (LDs; 16 h light:8 h dark) for varying durations [group 2 (LD-pM) – SD 17 d + LD 7 d; group 3 (LD-M) – SD 6 d + LD 18 d]. A group of photorefractory buntings previously maintained on LDs were simultaneously housed individually in activity recording cages and maintained on the same long photoperiod for the next 24 d (LD-R). On d 25, all birds were humanely killed and tissues collected for measurement of gene expressions. B, C) Change in activity behavior with photoperiod-induced seasonal phenotypes. Representative double-plotted activity record (B, actogram) and percentage daily activity distribution between light day and dark period (C) in black-headed buntings with photoperiodically induced seasonal states under SDs (Ba, Ca, SD-S) and LDs (Bb, Cb, LD-pM; Bc, Cc, LD-M; Bd, Cd, LD-R). Gray boxed portion of actogram (B) indicates 7 d segment for which total activity during day and night was calculated. Asterisk on bar (C) indicates significant difference in distribution of activity between light and dark periods of 24 h LD cycle (P < 0.05, Bonferroni correction).