Genesis 8:7

and he sent forth a raven, which went forth to and fro until the waters were dried up from off the earth. Forty days after the summits of the highlands had become visible, Noah opened the window of the ark, that is, he took away the screen from the light-opening and let a raven fly out, his intention being to find out whether it were possible for birds to find the necessary food on the earth by this time. But this experiment was not satisfactory, since the raven went forth and returned, probably feeding on the carrion which he found and then returning for his mate, without, however, becoming an inmate of the ark again.