Altered light conditions during spring: effects on timing of migration and reproduction in migratory redheaded bunting (Emberiza bruniceps)

Photoperiod is the most consistent environmental cue, and therefore, any change in anticipated light environment may affect subsequent response under long days. To test this hypothesis, photosensitive migratory redheaded buntings (Emberiza bruniceps) were exposed to altered photoperiods for 4weeks [short days (SP, 8L:16D, group 1; control), short days alternated with constant dim light (SP/LLdim; group 2), constant dim light (LLdim; group 3) and constant bright light (LLbright; group 4)] before being transferred to long days (LP; 16L:8D) for 15weeks. Group differences in long-day-induced responses were observed. The onset of migratory restlessness (Zugunruhe) was earliest in LLbright but persisted for maximum period in LLdim group. The LLdim group attained peak testis size significantly delayed and had more food consumption under long days. The results suggest that the altered photoperiodic exposure during photosensitive stage affects the seasonal phenotypes such as migration and reproduction in migratory buntings.