Amaterasu and the Rooster Perches
According to Shinto legend, Amaterasu, the sun goddess, was having trouble with her brother who was wrecking her gardens. She hid herself from him and thus there was only darkness. The Council of the Gods decided to put up a bird perch outside her door for the rooster to call out the day. They thought that such a thing would coax her to come out and thereby bring back the light. "Bird perch" is the meaning of the old Japanese word toreii. The rooster crows three times each morning, therefore three toreii gates lead to the Shinto shrine. As the rooster prepares for the day, the three toreiis prepare the heart of the worshiper as he passes through, approaching his shrine.
Source: Okinawa: a tiger by the tail by M. D. Morris
In March, 2014 Dr. Bung and I visited the shrines at Nominoue. Seen here are some of the toreii that are encountered along the way.