At any moment now, four very special birds will return to the UK for the summer.

Their arrival is eagerly awaited, for the information they carry could revolutionise what we know about migration.

Clement, Martin, Kasper, Lyster and Chris set out from England last summer as unknown cuckoos.

But thousands of miles later, these birds have become the famous five as their exploits captured the imagination of the public. Disaster and death en-route to Africa and back reduced the ‘famous five’ to the ‘fab four’, but the information captured during individual flights will guarantee their journeys are never forgotten.

The reason why these birds have become avian A-listers is because scientists are desperately worried about our cuckoos.

Cuculus canorus is disappearing fast. We have lost half of our breeding birds in the last 25 years alone.

Their call, a sound synonymous with spring and summer, has sadly disappeared from large swathes of our countryside.

Previously, scientists had little idea of what happened to our cuckoos once they left the relative safety of UK.

So last year, a scheme led by the British Trust for Ornithology (BTO) was unleashed to find out just what fate was befalling them.

Five birds were netted in Norfolk last May and fitted with 5g solar-powered satellite trackers. It was hoped the trackers would reveal vital information such as which routes the birds took, the duration of key stages of their journeys and the locations of important re-fuelling sites.

If scientists could harness this vital data, it might inform them how best to conserve the birds in the future.

Updates of the cuckoos’ locations were revealed every few days from the transmitters and the scheme quickly began to attract interest.

Each bird had a dedicated blog updated by scientists featuring the latest migration news and email updates were sent to cuckoo addicts revealing how they were faring.

There were moments of high tension. Birds would disappear for days on end, leaving followers on tenterhooks, only for the individuals to turn up safe and sound hundreds of miles from where the last transmission was sent.

The project’s runaway popularity has surprised everyone involved.

The BTO’s Paul Stancliffe said: “People have become attached to the birds, which has definitely helped with media coverage.

“We always thought that there was a lot of potential for this to be a big story but are still a little surprised just how big it has been.”

But on March 22, news came through from Cameroon that everyone had feared. Clement, named after the BTO’s director, was declared dead. The famous five had become the fab four.

But Clement’s death was not in vain, the project is already starting to unearth some surprising results.

The first shock for researchers was how early the birds left the UK last summer.

Three birds had departed England by the end of June and the last to leave was gone by July 22 — the cuckoos were only spending about a quarter of the year here.

The next surprise was how varied the cuckoos’ routes were.

Rather than all following a similar migration path, the birds all took dramatically different courses.

Lyster and Clement headed south across the Channel and then travelled down through France and Spain — in doing so they revealed a new migration route.

They then travelled on into Africa —minimising the risks of crossing the migrant death trap that is the Sahara by skirting its western edge.

By following this route they became the first British cuckoos ever recorded in West Africa.

The other three birds followed a more typical path, heading down through Italy and resting in the Po Delta — a vitally important re-fuelling spot for migrating birds.

The cuckoos then headed off into North Africa, crossing the vast continent through its centre — with a much longer 2,000km journey straight through the heart of the mighty Sahara.

Clement also revealed that cuckoos cross the desert in the sweltering heat of the day as well as at night. During the afternoon of July 15 last year, he covered 337km of the Sahara in extreme heat.

The remaining four birds are due to return at any point. Chris, named after BBC Springwatch presenter Chris Packham, is currently leading the pack.

Stancliffe added: “The weather in southern Europe is not too good at present and is holding up a lot of our migrants.

“We think that the birds will come back to the area in Norfolk that they were tagged in but we can’t say this for sure.”

The cuckoos will have to get used to the limelight — the trackers will stay on them transmitting vital data for the next two or three years.

Plans are afoot for more cuckoos to join them. Scottish cuckoos are faring better than their English counterparts and several will be tagged this summer to find out why.

So if you are lucky enough to hear a cuckoo in the next few weeks, have a peek to see if it is wearing a tiny transmitter — if so, you are being serenaded by one of the fab four.

To find out about the famous five’s adventures, visit www.bto.org/science/migration/tracking-studies/cuckoo-tracking

  • Latest reports from the BTO show Chris and Lyster have returned to the UK.