Then he sent out a raven and it kept going back and forth until the waters were drying up from the land.
Genesis 8:7 TLV

Why a raven first? As a carrion eater, it would be satisfied with any piece of bare ground with something dead nearby, but Noah knew that there was some dry ground outside. Perhaps it was to make sure that all corruption had been washed away? The raven goes first to ensure that death is complete and the ground is ready to begin producing life.