Hilchos Maasei Hakarbanos 7:9

Anywhere on the altar is suitable for melikah, so long as the kohein sprinkles the bird’s blood below the dividing line. If he sprinkles it anywhere on the altar, it is valid so long as he put a little of the lifeblood below the dividing line.

Hilchos Maasei Hakarbanos 7:10

The upper half of southwest corner was used for three things and its lower half was used for three things. The lower half was used for the melikah of a bird sin offering, approaching the altar with a flour offering and pouring out on its base the remaining blood of burnt offerings, sin offerings that are eaten, guilt offerings and peace offerings. The upper half was used for the water libations on Succos, the wine libations (also on Succos) and bird burnt offerings when there are many. If the southeast corner cannot accommodate all of them, the kohanim would proceed to the southwest corner and do melikah there.