Dancing Cranes of Sweden Wild

Each year in the heart of southern Sweden,

a special lake hosts a natural spectacle.

It's a stop off point for thousands of cranes migrating north.

A sight in itself, but when the moment is just right,

the cranes stage a remarkable performance which once seen is never forgotten.

The dance of the cranes.

It's the end of March in Sweden,

and at Lake Hornborga, spring should have arrived.

But this winter has been one of the worst in recent memory.

Half a metre of ice has covered the shallow lake for months, and snow still lies on the ground.

But regardless of this, the cranes have already started to arrive.

They have spent the winter in sunny Spain, but their breeding grounds are in northern Scandinavia.

Gliding in gracefully, they take their place on the stage.

When it's warmer and all of the cranes have arrived, the show will begin.

The dance they perform will be between couples,

and will strengthen relationships prior to breeding.

But for now, food is the first priority.

And food is the main reason the cranes first chose to come here.

These fields were once full of potatoes, the perfect fuel for migrating cranes.

When the farmers here stopped growing potatoes,

they were so attached to these visitors that they fed them grain instead.

And today, the cranes continue to be fed, ensuring that they return to the lake each year.

As April arrives, more and more cranes show up at the lake.

With them, they have finally brought the spring.

Their performance is just days away.

The ice on the lake has melted, and in the open water other visitors have gathered.

Whooper swans also stop off on their journey north.

And great crested grebes have arrived, already showing signs of courtship.

As each day draws to an end, the cranes head off to their roosting ground at the north end of the lake.

But come the morning, they'll be back for more grain.

Lake Hornborga is a big success story in Sweden.

Over many years, farming practices had made water levels drop.

There was little left of the lake apart from boggy, scrub-filled fields.

But in recent years, scrub has been cleared and water levels restored.

The cranes are well looked after.

It's mid-April and the number of cranes has peaked at around 10,000.

Nobody knows exactly what triggers the dance, but for whatever reason,

the cranes still don't quite seem ready for their curtain call.

With so many birds in such a small area,

it's easy to understand why they have to be fed.

And these are big birds, taller than most men.

They have an appetite to match their considerable size.

The cranes soon pick out all the grain from the grassy banks.

It will give them the energy they need to continue the journey north.

The numbers of whooper swans on the lake have also reached a peak.

The lake is getting crowded.

With less space, males become more aggressive.

They too are preparing to breed.

But the swans are the supporting act.

The stars are now ready for the show to begin.

It is the climax of the gathering at Lake Hornborga.

The dance of the cranes.

Cranes mate for life, so some will have joined their partners

in this display for as many as 20 years.

Like us, some are better dancers than others.

But whether clumsy or graceful,

the dance affirms bonds between couples like a renewal of vows.

The whole performance ensures that that when they reach the breeding grounds,

they will be ready to get straight to the business of raising a family.

With the dance completed, the time has come for the cranes to move on.

Their breeding site is much further north.

When conditions are right,

they take off and fly up to great heights, using thermals for lift.

Gradually as more and more leave, the numbers at the lake dwindle.

By the end of April, the cranes will have gone.

But the show must go on.

In autumn they will stop off at the lake on their return journey south,

with some new troop members in training for next season's performance.

And with a little help from man to ensure this site provides food

and shelter, this will continue to be the lake of the dancing cranes.