Leviticus 1:14-16

14"If his offering to the Lord is a burnt offering of birds, then he shall bring his offering of turtledoves or pigeons.

15And the priest shall bring it to the altar and wring off its head and burn it on the altar. Its blood shall be drained out on the side of the altar.

16He shall remove its crop with its contents and cast it beside the altar on the east side, in the place for ashes.