I have seen, and have testified that this is the Son of God."

 In Palestine the dove was a sacred bird. It was not hunted and it was not eaten. Philo noticed the number of doves at Ascalon, because it was not permitted to catch and kill them, and they were tame. In Genesis 1:2 we read of the creative Spirit of God moving upon the face of the waters. The Rabbis used to say that the Spirit of God moved and fluttered like a dove over the ancient chaos breathing order and beauty into it. The picture of the dove was one which the Jews knew and loved. 