Genesis 15:11

The fowls came down. This was, of course, a real occurrence and not merely a vision or dream. The reality of Abram’s fulfilling the divine directives is implied by the fact that he had to drive away birds of prey that tried to feed on the carcasses. If they are not prevented from doing so, vultures and other birds, in Oriental lands, begin to consume fallen animals immediately upon their death, usually picking their bones clean within a matter of minutes. Abram reverently walked between the severed parts of the sacrifice, according to custom, yet there was no visible evidence that God on His part accepted the obligations of the covenant. This was to come later (v. 17). But until then Abram felt it his duty to protect the carcasses from being torn to pieces and devoured (PP 137).