Hi Joel
I don't know too much about vultures, but having grown up in the area there are one or two things I do know:
1. There is an old breeding site (Cape Vultures) between Middleburg and Cradock near a farm called Tafelberg and I have heard that after a huge decline in the number of vultures at this site they are on the increase. I read an interesting article about a study which was conducted at this site and it was found that these birds travel hundreds of kilometers to Kruger and back to feed their chicks (but this was years ago!)
2. I have seen Cape Vultures in MZNP (four times) and AENP (once) - no others
3. These sightings are all fairly recent - within the last three years - despite having visited both MZNP and AENP since I was young
4. We have a farm in the area and have been seeing more and more Cape Vultures in the area in the past +/- 3 years. - a neighbour actually came across the remains of a Cape Vulture which had flown into powerlines on his farm two weeks ago - tragic!!
5. I presume this increase has something to do with the introduction of more and more apex predators in the Eastern Cape (in private reserves and SANParks)
I will leave the rest to the experts (I'm sure there is someone on the forum who can answer all your questions!)