Ramban on Genesis 15:11/רמב"ן על בראשית ט״ו:י״א

1AND THE BIRDS OF PREY CAME DOWN UPON THE CARCASSES. [They came down] to eat them, as is the nature of birds.

2AND ABRAM DROVE THEM AWAY. It was thus alluded to Abraham that the nations would come to abolish the sacrifices, but the children of Abraham would drive them away.