Leviticus 1:14-16

14“If his offering to the Lord is a burnt offering of birds, he is to present his offering from the turtledoves or young pigeons.

15Then the priest is to bring it to the altar, and will twist off its head and burn it on the altar; its blood should be drained at the side of the altar.

16He will remove its digestive tract, cutting off the tail feathers, and throw it on the east side of the altar at the place for ashes.