Tagged cuckoo 'missing in action'
One of the five British Cuckoos fitted with satellite tags by the British Trust for Ornithology (BTO) almost a year ago has disappeared.
The BTO say they received their last transmission from the bird, which the researchers named Clement, on 25 February this year.
His last known location was Cameroon.
The team say that Clement had begun his journey back to the UK after making it safely to his winter home in sub-Saharan Africa.
End Quote Andy Clements BTO
Let's hope his colleagues all make it back to the UK safely”
The BTO said: "Other tagged cuckoos have gone missing only to reappear at a later date, [but] analysis of the data by BTO scientists show that he is almost certainly dead."
Between 1995 and 2010 the population of cuckoos spending summer in the UK fell by almost half. The team embarked on their satellite tracking project in an attempt to find out more about the birds' migration routes and to shed light on the possible causes of this decline.
The BTO said that Clement made "ornothilogical history"; he was the first British Cuckoo found to take a western migration route - crossing from Europe to Africa via Spain rather than Italy.
From North Africa he made his way to Senegal, before joining the other four tagged Cuckoos in the Congo rainforest. Until then, the wintering sites of British Cuckoos had been something of a mystery.
Andy Clements, director of the BTO, and Clement's namesake, said Clement's demise was "sad news", but that thanks to the tagged birds, the organisation had "gathered extraordinary data about Cuckoo migration".
"Let's hope his colleagues all make it back to the UK safely," he added.
According to a 2010 survey by the Royal Society for the Protection of Birds (RSPB), of the 10 UK birds that have declined the most since 1995, eight are summer migrants, including the cuckoo, turtle dove, yellow wagtail and nightingale.
Grahame Madge, an RSPB spokesman, told BBC Nature: "There is an urgency with cuckoos because they are dwindling so fast.
"All individual birds die at some time, but the important thing here is that scientists are working towards the survival of a rapidly-declining species."