Every July the wildebeest, those ungainly, yet endearing animals, migrate north in vast numbers from the Serengeti plains in search of fresh pasture, and return south around October. The Maasai Mara is by far the best-watered part of the 28000 km² eco-system of the Serengeti. The Great Migration is one of the most spectacular wildlife experiences nature has to offer, involving an immensity of herbivores: some 1,300,000 wildebeest, 360,000 Thomson's gazelle, and 200,000 zebras. These numerous migrants are followed along their annual circular route by hungry predators, most notably lions, cheetahs and hyenas.
A dangerous barrier for the migratory zebras and wildebeest is the Mara River, with the largest crocodiles found in East Africa. The crossing of the river by these herds is one of the most fabulous times of the Great Migration. It is not rare to find photographers, film makers and animal lovers waiting for days by the river to view the animals crossing. 

Additionally, some 450 species of birdlife have been identified in the park, including vulture, marabou, secretary bird, hornbill, crowned crane, ostrich, long-crested eagle, and pygmy falcon.