Chickens: family Pheasantidae of the order Ornithischiaceae. It is the most common domestic fowl kept by humans. Domestic chickens are originally from the wild original chicken, the original domestication as poultry purpose is to provide people with a variety of special eggs, meat and other food, to provide people with cheap high-quality animal protein. Its domestication history is at least about 4,000 years old, but it was not until around 1800 that chicken meat and eggs became mass-produced commodities. It ranks 10th in the 12 zodiac signs.

Biological characteristics: body temperature, between 40.9 and 41.9 degrees, with an average body temperature of 41.5 degrees. The chicks, however, are bred with a high chick house temperature requirement, usually at thirty-four or fifteen degrees.

Reproductive system: the reproductive system of chickens is different from that of fetal mammals. The testes and epididymis of the rooster are in the abdominal cavity, the mating organ is a degenerated genital protuberance, and the sperm head is long conical. Sperm can survive for up to 24 days in the nest of sperm glands in the hen's oviduct and are capable of fertilization.

Rooster crowing: The rooster's crowing is a kind of "declaration of sovereignty," reminding family members of its supremacy on the one hand, and warning neighboring roosters to keep out of its family's way on the other. The rooster crows about once an hour during the day, but the first crow in the morning breaks the silence of the dawn, and the neighboring roosters take over, making a lasting impression. Typically, chickens sleep at night. Chickens have a "pineal gland" in their brains. The pineal gland secretes a substance called melatonin. If there is light in the eyes, the secretion of melatonin is suppressed. Melatonin inhibits the production of sex hormones and directly controls bird song. When the morning light appears, the secretion of melatonin is suppressed, and the male chickens can not help but "morning"; during the year, when the day is getting longer, the melatonin level in the bird's body decreases, and they begin to "call spring". The grandfather with the birdcage in the park also knows this, usually the birdcage is covered by a thick cloth cover, once the cover is removed, the light wakes up the bird's "chirping center" and the singing will begin. In ancient times, roosters could enjoy the darkness and silence of the night. Sometimes, when there was a full moon, the moonlight would occasionally stimulate the overly sensitive rooster to "wake up". And when the war, the sound and fire alarmed by the rooster night crowing probability increased greatly, so the ancient people to "rooster night crowing" as the omen of war.