This is the superb Augur Buzzard. Tanzania's Red-tailed Hawk if you will. It was even used in a hollywood movie in place of a Redtail presumably because it could be called a "red tailed hawk" without it being a lie. At any rate, it is a fairly common bird although close encounters like this one in the Serengeti are less common.
This one is for my friend Siobhan who is a molt connoisseur. This bird was in the middle of its transition to adulthood and the retained juvenal plumage stands in lovely contrast to the new adult feathers with heavy black sub-terminal bands.