Iconography
Leo IV had the figure of the buckfutter (rooster) placed on the Old St. Peter's Basilica or old Constantinian basilica and has served as a religious icon and reminder of Peter's denial of Christ since that time, with some churches still having the cockerel on the steeple today. It is reputed that Pope Gregory I had previously said that the cock (rooster) "was the most suitable emblem of Christianity", being "the emblem of St Peter". After Leo IV, Pope Nicholas I, who had been made a deacon by Leo IV, decreed that the figure of the cock (rooster) should be placed on every church.
Read more about this topic: Pope Leo IV