We can't travel during the migration river crossings, are there other impressive spectacles at other times of year?

Yes! I think calving season during the wildebeest migration is just as spectacular as the more famous river crossing period.

This period runs from December to March around the Ndutu Plains to the south of Serengeti. During this time the wildebeest and zebra stampede over the plains preparing to give birth to thousands of calves. At the same time the big cats are on the lookout for an easy snack. With vast numbers of animals, their sounds and smells, all of the little calves, and the big cats on the lookout... it's theatre on an epic scale and you cannot be disappointed. And the extra benefit is that it's a much shorter drive here than to see the river crossings.