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© BTOTrying to tell us something? Clement the cuckoo has already migrated to Africa, where he spends each winter. The tracking device can be seen on his back
It seems the chances of a warm British summer are doomed if the migratory movements of a cuckoo are anything to go by.

So unimpressed with our mild climate is Clement the cuckoo that he has already flown to Africa, where he spends each winter.

He is one of five cuckoos that scientists are tracking on their southward migration, and the first to have left Europe altogether.

Three of the others are currently in Italy, while the last has remained in East Anglia, where all five were caught and tagged with fingernail-sized tracking devices in May.

The British Trust for Ornithology (BTO) is monitoring the birds in order to work out why their population has dramatically fallen over the last few years.

The adventurous Clement left Britain on June 3, a month before ornithologists had thought the cuckoos would begin their migration.

He then surprised researchers by taking a westward route, flying over France before heading west through Spain and then crossing the Mediterranean into Algeria.

Scientists had expected all the cuckoos to travel on an easterly route down the length of Italy.

Clement - named after the BTO's director Andrew Clement - is now thought to be resting in the Atlas mountains before he prepares to cross the Sahara, a journey which undertaken at night to avoid the extreme heat of the desert.

Kasper, Martin and Chris, three other birds tagged as part of the project, took the orthodox route down Italy. Kasper was last monitored near Rome, while Martin and Chris are both thought to be around the River Po in northern Italy.

The fifth cuckoo, Lyster, has stayed in southern Norfolk for the last two months, but is expected to start his migration soon.

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© UnknownFlight paths: The British Trust for Ornithology is monitoring the cuckoos' movements in order to work out why their population has dramatically fallen over the last few years
The researchers hope to explain why cuckoo numbers have plummeted by two-thirds in the last 25 years, leaving as few as 7,000 breeding pairs migrating here from Africa each spring.

Scientists have so far been unable to explain this catastrophic decline in the number of birds whose annual visits are part of our folklore, and there are now real concerns about the cuckoo's future.

Possible explanations include a fall in the population of the caterpillars which provide the cuckoo's diet while in Britain, or the destruction of their African habitats.

However, no-one is currently sure where in Africa British cuckoos spend the winter - or how much they move around when they get there.

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© AlamyDestination: Clement has made his way to the Atlas mountains in Algeria
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© AlamyThe researchers hope to explain why cuckoo numbers have plummeted by two-thirds in the last 25 years, leaving as few as 7,000 breeding pairs migrating here from Africa each spring
The tags fitted to these birds transmit location data for ten hours, before shutting off to recharge their batteries using solar energy for two days. They are expected to continue sending data to scientists for the next three years.

Chris Hewson, research ecologist at the BTO, said: 'People have been putting tags on birds for over 100 years but haven't got a very good idea of where they go, let alone what they do.

'So all the information we get from this will be very important in understanding what's going on.'

All of the five cuckoos tagged are male, but if money can be raised for more of the £2,500 tags, female birds could also be tracked in years to come.

The cuckoos' progress can be followed on 'their' blogs on the BTO website.