Starting in mid-February, half a million sandhill cranes turn an unassuming part of the US Midwest into the setting for one of North America’s greatest wildlife spectacles.

Like clockwork each year, starting around Valentine’s Day on 14 February and peaking around St Patrick’s Day on 17 March through early April, hundreds of thousands of sandhill cranes fly to the Big Bend in Nebraska’s Platte River, turning a rather unassuming part of the US Midwest into the setting for one of North America’s greatest wildlife spectacles.

This 75- to 80-mile stretch of river between the Nebraska towns of Grand Island and Kearney will see more than half a million birds – nearly 80% of the world’s population of sandhill cranes – pass through during their spring migration. The large grey-feathered birds, known for the bright red skin above their eyes, a loud trilling call that can be heard up to a mile away, and a wingspan of up to 7ft, travel around 350 miles a day from Texas, Oklahoma or Mexico to stop in Nebraska on their way to their breeding grounds, which are spread across the northern United States and Canada. Returning to within feet of their original nesting sites, the birds will travel upwards of 1,000 miles during a migration.

The sight and sound of nearly the entire population of the world’s oldest living bird species is awe inspiring, and the best way to see it is from a river viewing blind – a camouflaged, long wooden room with window panels built near the edge of the river. For the best views of the cranes, head to the blinds at the 1,150-acre Rowe Sanctuary, about 20 miles southeast of Kearney.

You will need to be in place well before sunrise, which means arriving at Rowe Sanctuary around 5 am, dressed in warm clothes and ready to stand quietly for about two hours with the other eager birders and photographers who may have waited their entire lives to witness the spectacle.

Long before you can see the birds along the river, you can hear them. Calling to each other through the night, the birds do not ever seem to stay quiet. Amazingly, a mother can distinguish her baby’s call and a male can hear his mate from amid the cacophony. When the sun starts to rise and the indistinct black shapes dotting the river as far as you can see come into focus, the noise will, incredibly, increase as all the birds begin to wake up.

Without warning, or at least without one that you can determine, nearly an entire roost, hundreds of birds, will take flight at once in a whoosh of wings and trills that will take your breath away. And when the early morning sunlight hits the underside of their wings, they take on a golden glow. Circling over the river, continuously calling out to each other, they will eventually fly to a nearby field and spend the day gorging on corn.

They are here, after all, to gain weight and energy for their long journey north. They will put on one-fifth of their body weight, about 1lb to 2lb, during the month or so that they stay. The cranes are also here to start forming pairs. Sandhill cranes mate for life, and if it is their first mating season, the bonding begins around the time they get to Nebraska.

One of the ways they connect with a future mate is through dancing. From a single crane bowing alone to a mated pair jumping and turning around one another, each dance has a meaning. A young, single crane throwing a piece of straw into the air for a potential mate is saying, “Look at me. I can build you a good nest.” Throwing their wings out, twirling, curtseying and hopping energetically from foot to foot, cranes do not dance solely to find a partner, they also do it to relieve stress; young ones will imitate parents or other older cranes dancing, and some naturalists theorize they dance to express emotion or just for the fun of it.

It is not about all dancing and getting fat, though; the arrival of the cranes means the arrival of a food source for predators. And with patience and binoculars, you can watch the drama of nature unfold before you. Bald eagles, for example, will prey on any cranes that are injured or left behind when the roosts fly to the fields for feeding.

Near dusk, another good viewing time, the cranes will gather on the sandbars in the river, reversing their grand morning exit. The further they are from the river banks, the lesser their chance of getting attacked, so the sandbars in the middle of the river fill up first, with the birds jostling for a good place. If a predator tries to get close, the water acts like an alarm system and alerts them of any danger. And the cranes can fight back; their talons and beak are surprisingly effective at taking out a fox, bobcat or coyote.

For pioneers making their way west during the 19th Century, the Platte River was known as being “a mile wide and an inch deep”. As a braided river, typified by shallow, meandering channels separated by sandbars, it is an ideal crane habitat. But today, only the Big Bend portion of the river can support the large crane population. Over time, the channel has been altered, wetlands drained and the flow of the water controlled and diverted for use in nearby cities and farms. This means the spring floods that cleared the river of vegetation no longer happen, making it difficult for the cranes to use the length of the river to roost out of range of most predators. This makes for spectacular and guaranteed crane viewing, but also means that ongoing projects, including clearing vegetation off the sandbars with heavy machinery each year, are needed to protect this last stretch of habitat, not just for sandhill cranes but also for the endangered whooping cranes who migrate through the area around the same time, and of which there are only 300 left in the wild. As important as the Platte River is for the cranes’ survival, the birds do not stay in the area long. After putting on some weight, when they feel a warm updraft of wind beneath their wings sometime around early April, it is time to continue moving north. And it will be another year before they all return.

Rowe Sanctuary runs crane viewings ($25 per person) every morning and evening from 2 March to 7 April when the crane numbers are at their peak (reservations required); before or after those dates head to the public bridges along the river to see the birds. You can celebrate the birds and learn more about them at the Nebraska Crane Festival from 21 to 24 March, hosted by the Nebraska branch of the Audubon Society. And Kearney hosts the Crane Watch Festival between 22 and 31 March, with events such as tours to the viewing blinds and crane cake decorating contests.