Mark 1:9-11 says:
9 And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan. 10 And straightway coming up out of the water, he saw the heavens opened, and the Spirit like a dove descending upon him: 11 And there came a voice from heaven, saying, Thou art my beloved Son, in whom I am well pleased.
Jesus receives The Holy Spirit and it came down on Him like a Dove. The Dove symbolizes The Holy Spirit.
De dove also symbolizes peace.