A few good habits do more for migration photography than costly equipment. The best light for wildlife usually comes at golden hour, meaning the hour following sunrise and the hour preceding sunset. Build your game-drive schedule so you're in position then, rather than hoping it lines up by chance.
For gear, use a beanbag instead of a tripod when you're in a moving safari vehicle. Any properly run photographic safari carries one as standard equipment. If you've never tried it, get comfortable with it first, so it doesn't let you down at a crossing you may see only once.
Here's the key shift in thinking: stay patient at one carefully chosen spot, and your pictures will usually beat those taken by moving from sighting to sighting. A guide willing to hold position near a probable crossing, rather than racing after every reported sighting, often makes the difference between a great photo and a handful of rushed, faraway ones.
Our camera gear guide has more, or browse our photographic safari itineraries.