In late November and December, the herds arrive on the short-grass plains of the southern Serengeti, around Ndutu and into the northern Ngorongoro Conservation Area, dispersed across the plains feeding on fresh, nutritious grasses. They stay here through January, February and March.

This is calving season, and it is extraordinary. Over 500,000 wildebeest calves are born during this period, with around 8,000 calves born per day at peak. The strategy is ancient and deliberate: by flooding the plains with newborns simultaneously, the odds of any individual calf surviving improve dramatically. Predators eat their fill and the rest survive. The result is exceptional predator activity alongside scenes of new life that are, frankly, difficult to prepare yourself for.

February is the peak. Mid-January and March offer almost the same experience with considerably fewer visitors.

Around April the herds start moving north. These can be long snaking herds (reaching lengths of 25miles! That’s 40 kilometers). By May, the wildebeest all seem to be moving together in a series of columns, often containing hundreds of thousands of animals joined by many zebra, moving through the area around Moru Kopjes and west of Seronera.

Rain plays a huge role in the wildebeest movements at this stage, as heavy rainfall promises lush vegetation and influences the pace and direction of the herds. The rutting (‘mating’) season is also in full swing during April and May — males jousting for dominance as the columns move. It is chaotic, hormonal, and spectacular in a completely different way from the calving season.

Interesting fact: males that did not mate will often go out on their own to create their own herds.

Around June the migration is often halted on the south side of the Grumeti River, which has channels that block or slow the northward movement. The wildebeest congregate here in the Western Corridor, often building up to high density before crossing. The river here is normally a series of pools and channels, and whilst it always represents an annual feast for the Grumeti River's large crocodiles, these crossings are not usually quite as spectacular as the Mara River crossings further north.

That said, "not as spectacular as the Mara crossings" is still very spectacular.

This is the chapter that made the migration famous. The wildebeest migration continues moving northwards during July and August, often spreading across a broad front — some heading through the Grumeti Reserve, others north through the heart of the Serengeti. September sees the herds spread out across the northern Serengeti, where the Mara River provides the migration with its most serious obstacle.

Watching the frantic herds cross the Mara River can be very spectacular, with scenes of great panic and confusion. It is common to see herds cross north one day and back south a few days later. They follow storms, flee predators, and respond to signals we cannot perceive. A crossing can happen in minutes. The buildup can take days. There is no crossing schedule. That unpredictability is part of what makes witnessing one feel like such an extraordinary piece of luck — even when you have planned carefully for it.

The herds in Kenya's Masai Mara are at their peak numbers from July through October, swelled by local wildebeest populations joining the migration. If you are planning a trip around the crossings, this is your window. Give yourself at least four nights.

By October the wildebeest herds are heading south with more accord, moving through western Loliondo and the Serengeti's Lobo area, returning to the green shoots which follow the rains on the short-grass plains of the southern Serengeti in November.

The southbound crossings of the Mara River in late October are often large and dramatic, and they happen with a fraction of the audience that the northbound crossings attract. Worth knowing.

By December the herds are back on the southern plains, the females heavily pregnant. The cycle is complete and immediately starts over.