After 8,000 miles, Martin the cuckoo is almost home

It's nearly here, the best-loved sound of spring, the double note of the cuckoo: in fact, it's in southern Spain, on the last leg of a 4,000-mile journey from Central Africa.

Click HERE to view 'Return flights' graphic

Doing the cuckooing is Martin, one of the five British cuckoos ringed in Norfolk last summer by the British Trust for Ornithology (BTO) and fitted with lightweight satellite transmitters to record their migration to and from their African wintering grounds.

After a tremendous nine-month odyssey involving a double crossing of the Sahara desert, Martin is the first bird to make it back to Europe, and in the last few days has crossed the Mediterranean from North Africa and is currently near the town of Lorca in the Spanish province of Murcia – or to put it in Easter Holiday terms, not far from the welcoming climes of the Costa Blanca.

Depending on the weather, and the absence of accidents, he will probably be back cuckooing in the countryside near Great Yarmouth, where he was caught on 19 May last year, some time in the next 10 days. With various diversions, he will have travelled more than 8,500 miles.

Following behind him on their Britain-bound paths are cuckoos Chris, Lyster and Kasper, but sadly not the fifth bird, Clement, which died at the end February of unknown causes in Cameroon – probably taken by a predator or perhaps by human hunters – having started his return journey like the others from the mid-winter resting place of all the birds in the dense forests of the Congo.

Chris has just crossed the Sahara and is thought to be in Algeria getting ready to sail out over the Med, while Lyster and Kasper are in Ghana and the Ivory Coast respectively, fattening themselves up for the exhausting 1200-mile desert crossing ahead of them.

Just what a feat of physical endurance this is for a bird was illustrated by the satellite telemetry of Martin's Sahara transition last Sunday. In one period – in the scorching heat of the day, with no shade on the bare sand below in which to rest and refuel – he flew more than 250 miles in four hours – meaning he was averaging more than 60mph. "He must have had a strong tailwind," said Dr Chris Hewson, one of the BTO scientists in charge of the project.

"I don't think a cuckoo could fly continuously at that speed for four hours by itself, but the birds may well be able to judge the best altitude to get a following wind to help them."

He added: "We are thrilled he has made it back to Europe and we are looking forward to welcoming all the birds back to Britain."

The difficulties, dangers and challenges of these journeys – the graphic, left, gives a vivid idea of their extraordinary scale –are the reasons behind the BTO experiment, designed to see if they may be contributing to the steep decline of the cuckoo in Britain, which dropped in numbers by 65 per cent between 1984 and 2009.

The birds may be vanishing because of problems here on their British breeding grounds, such as the disappearance of the moth caterpillars on which they largely feed. But it is just as possible that they are running into difficulties on their migrations, about which – until the current experiment – virtually nothing was known.

Now, a raft of information wholly new to science has become available about their routes, timings and stopover places, which scientists hope will aid cuckoo conservation in the future.