Black vultures have weaker beaks than raptorial birds, and as a consequence they can't crack through the tough hides and solid bones of a carcass. So they have to attack the softest body parts of their victims first -- the anus and eyeballs. No, that's not the gross part. You can't handle the gross part. Just ... there's some good stuff later about exploding penises -- maybe that's more your speed. Go check that out.
You really want to know? All righty. You insisted. Once the butthole buffet is depleted, the black vulture then burrows in through the devoured rectum to get at the rest of the tender innards. Think about that: Every time they get hungry, they have to dig an asshole tunnel using their mouths instead of shovels. If you really want to understand the plight of the black vulture, here's a fun little experiment: The next time you microwave a bean-and-cheese burrito, try poking a hole in one end and then shoving your whole head in there to eat it from the inside out, because the textures are probably pretty similar and -- oh goddamn it. We just ruined burritos for everybody, didn't we?
They were delicious, we know. We're so sorry.
We usually start at the stomach, but now their cold, dead ass just sits there, judging us.