It has been known from previous studies that crowing in roosters can be triggered by external stimuli like car headlights and crowing of other roosters apart from their crowing just before dawn.
Animal physiologist, Dr Takashi Yoshimura and his colleague set out to investigate the scientific explanation behind crowing in roosters. They experimented with 12 roosters by initially exposing them to 12 hours of light and 12 hours of darkness for two weeks. Later the roosters were constantly kept in dim light for two weeks. It was observed that in both the setups, the roosters crowed two to three hours before dawn.
Researchers also observed the behavior of the roosters to external stimuli like fluorescent light and recorded sound of other roosters crowing.
Yoshimura notes that crowing is mainly induced in the morning and the roosters are more sensitive to external stimuli in the morning.
The findings of the study are published in the journal, Current Biology.