It has been suggested that the early-morning surge in testosterone triggers crowing in roosters.A rooster is often portrayed crowing with its head high, displaying its brightly colored combs. Crowing is interpreted as a type of communication in these birds. Roosters may crow when they hear others crowing. They may crow in response to any sort of disturbance, like a loud sound or flash lights. They may crow on seeing a predator, as a warning for others. They may crow to attract the attention of other members of the group for foraging. This type of vocalization is also used to woo their mates.
In short, crowing of roosters is not restricted to pre-dawn hours. They may crow at any time, as and when they like. However, crowing at dawn is much more prominent in these birds. According to one theory, most birds are active during the morning, which is the time they sing and vocalize in different forms. Being birds, roosters are no different; however, early morning crowing in roosters is explained with various theories. Go through this Buzzle article for a brief overview of the same.
A rooster in a chicken flock is the one that guards and protects other members. The early morning crowing of a rooster is often interpreted as a warning signal for other roosters in the neighborhood, to stay away from the former's territory. The start of the day is the best time for such advertising, as these birds are diurnal (active during the day). It has also been noted that if there are more than one rooster in a flock, the dominant one has the authority to crow first.
Though roosters crow during other times of the day (as well as night), this behavior is more explicit before sunrise. This gives rise to the doubt about the link between early morning sunlight and rooster crowing. It has been suggested that an increase in light could be the reason behind this behavior. However, roosters may crow in the middle of the night, when the lights are turned on. If any type of light can trigger a rooster to crow, then what is the factor that causes its early morning crowing behavior. The phenomenon as explained by some Japanese scientists, is given below.
According to a recent research conducted by animal physiology researchers Tsuyoshi Shimmura and Takashi Yoshimura of Nagoya University in Japan, light is not the factor that triggers early morning crowing in roosters. As per their experiments, roosters have their own internal clocks or circadian rhythm that helps them know the time of the day. The study was conducted on two groups of roosters, that were kept in different sound-proof chambers with different light conditions. The chambers were equipped with sound recorders and video cameras.
Experiment 1: The birds in the first chamber were subjected to 12 hours of continuous bright light followed by 12 hours of dim light. The roosters started crowing two hours before the onset of bright light. Occasional crowing was noticed with sudden flash lights or with recorded crowing of other roosters. However, even these triggers induced high-frequency crowing, when activated during pre-dawn hours. In other words, these stimuli triggered only a mild response from the roosters during other times of the day, but the response was much stronger during dawn.
Experiment 2: The second group of birds were subjected to 24 hours of dim light. The crowing pattern of these birds was recorded throughout the day. Though they crowed occasionally throughout this period, its frequency increased at a specific time, which they thought was dawn. Everyday, the roosters crowed at the same time, at a gap of 24 hours. However, after two weeks, this interval became irregular and they started crowing at different times of the day.
- Internal Body Clock: From the experiments, it has been proved that roosters have a special internal mechanism (circadian rhythm) that is much more prominent than the external stimuli (like sunlight), when it comes to crowing. This is proved with the fact that they crowed at dawn, even though they were not exposed to sunlight or the outer world for days together.
- Sunlight: So, roosters mostly follow their internal body clock, and rely less on external stimuli. But, it is possible that their body clock is set according to external stimuli. In case of the second experiment, the roosters followed their body clock and crowed at the same time, everyday. But, after two weeks, their crowing become irregular. This suggests that may be required to see sunlight and dawn, so that their internal clock is set properly.
- Pre-dawn Hours: Even though they respond to stimuli, like the headlight of a car, the intensity of such response would be much higher during the dawn, as compared to other times of the day.
In short, it is the circadian rhythm or the internal body clock that is the main factor that trigger roosters to crow in the morning. However, these birds may take cues from external stimuli, like sunrise to tune their body clock to function properly. Their crowing behavior is very prominent during the early morning hours, as compared to other times of the day. Further studies about this curious behavior in roosters are still underway.