For thousands of years, roosters have served as nature's alarm clock. The cock-a-doodle-doo serves as a claim to territory at light's first break. One crow triggers a cascade of calls.

But who initiates the domino effect of cock-a-doodle-dooing?

New research out of Japan suggests the most dominant rooster of a localized group is always the first to announce the sun (and his territory). Chickens are social animals, and like hens, roosters maintain a social hierarchy, or pecking order.

The term "pecking order" is derived from our understanding of chicken society, where the term very literally describes the birds' social structure. Within a group of hens, the dominant bird asserts her superiority via pecks. All beneath her are fair game. The second-ranking hen will peck all the other birds aside from her superior. The bottom bird is out of luck.

Roosters maintain a similar hierarchy. In addition to first dibs on the dawn-announcing yodel, the highest ranking rooster is also first to eat and mate. Researchers Tsuyoshi Shimmura and Takashi Yoshimura, of Nagoya University, found this to be so after many hours spent observing a group of roosters.

After identifying the social order, Shimmura and Yoshimura removed the highest ranking rooster and found that the second-in-command took over inaugural crowing duties.

We have discovered that roosters live in a strictly linear hierarchy, where social ranking reflects the order to announce the break of dawn," Yoshimura said in a press release.

The researchers, whose new work is published in the journal Scientific Reports, previously showed that roosters can accurately announce the coming of the sun in a dark room -- proving the roosters rely on internal biological clocks.