Leviticus 1:14-16

14 And if his offering to the Lord is a burned offering of birds, then he is to make his offering of doves or of young pigeons.

15 And the priest is to take it to the altar, and after its head has been twisted off, it is to be burned on the altar, and its blood drained out on the side of the altar:

16 And he is to take away its stomach, with its feathers, and put it down by the east side of the altar, where the burned waste is put: