After these 'forty days', it would be during the eleventh month when Noah opened the window of the Ark. Again, forty means probation in Biblical numerics.
     This 'raven' was one of the two unclean fowls aboard the Ark.

 

 Lev.11: 1 And the Lord spake unto Moses and to Aaron saying unto them. 2 Speak unto the children of Israel, saying, These are the beasts which ye shall eat among all the beast that are on the earth...

 

 Deut.14: For thou art an holy people unto the Lord thy God, and the Lord hath chosen thee to be a peculiar people unto Himself, above all the nations that are upon the earth.

 

And it includes the raven as unclean to eat. This raven will not return back to Noah's Ark. So it must have found carcass for scavenging.

Gen 8:8   Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground;
9    But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark.

     Noah sent a dove also when he sent the raven. The dove, as written here, returned back to the Ark. The dove is a symbol for the Holy Spirit, even descending as a dove on Christ Jesus after He was baptized.

 

 Matt.3: In those days came John the Baptist, preaching in the wilderness of Judea... 17 And lo a voice from heaven, saying, “This is My beloved Son, in Whom I am well pleased.

     The dove is a clean fowl which may be eaten...

 

 Deut.14:11: Of all clean birds ye shall eat.

 

Thus we have two particular symbols representing two groups, one in the 'scavenger' sense for the raven, and the other as a dove for a clean sacrificial fowl, representing The Holy Spirit. The 'scavenger' found food aplenty, but the dove did not, and had to return to the Ark (of God's Protection).

Gen 8:10   And he stayed yet other seven days; and again he sent forth the dove out of the ark;
11    And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth.
12    And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more.

     'Seven days' for spiritual perfection. This time the dove brought a leaf from an olive tree. This olive leaf was freshly picked, as that's the meaning of 'pluckt off' (Hebrew 'taraph'; Strong's no. 2965). The dove found dry ground, meaning the waters had fully subsided off the earth, and new growth (olive leaf) had already been re-established.

 

Gen 8:13    And it came to pass in the six hundredth and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering of the ark, and looked, and, behold, the face of the ground was dry.
14    And in the second month, on the seven and twentieth day of the month, was the earth dried.