Scientists in Japan have discovered that the dawn crowing of a rooster is controlled by their internal body clocks, not just by the rising of the sun.
In the 12-hour situation, the birds began to crow about 2 hours before the light was switched on, just as they do in the wild. And when kept under only dim-light they also still crowed most at the pre-dawn period, indicating that they instinctively knew when to crow, even in the absence of any light cue.
Shimmura and Yoshimura also found in these low-light exposed birds that, with each successive day, the cocks crowed a little bit earlier each day. This is a characteristic sign that a process is under internal clock control.
Delivered later in the day, however, these stimuli elicited far fewer responses. Moreover, if the stimuli were given during the night-time, the roosters didn’t crow at all. This suggests that not only the pre-dawn crow, but also, light and sound–induced crowing, is under the control of the rooster’s own body clock.
So, more accurately, we should be talking about clock-a-doodle-doo from these birds...