Roosters crow at dawn due to their internal clock and not the rising sun, researchers have found.
" 'Cock-a-doodle-doo' symbolizes the break of dawn in many countries," scientist Takashi Yoshimura of Nagoya University said in a statement, according to LiveScience. "But it wasn't clear whether crowing is under the control of a biological clock or is simply a response to external stimuli."










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