Tagged cuckoos complete migration and return to the UK
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Tracking devices fitted to five cuckoos have revealed the remarkable annual journey of a bird that heralds the arrival of the UK's spring.
The male birds were fitted with the satellite tags last May by scientists from the British Trust for Ornithology (BTO).
Two cuckoos, Lyster and Chris arrived back in the UK this week - the first to have their African migration mapped.
After a 10,000 mile trip, Lyster was seen 10 miles from where he was tagged.
Phil Atkinson, head of international research at the BTO spotted the cuckoo in the Norfolk Broads on Tuesday.
"We saw him flying past - you can see the wire antenna poking out [from his tag], so it was definitely him," he told BBC Nature.
"It's just fantastic; we know where he's been, we know the routes he's taken and now he's back in the broads."
The aim of the project was to discover why, each year, fewer and fewer of the birds return to the UK.
Britain has lost almost half of its cuckoos in the last two decades and the population of the birds is continuing to decline steadily.
The lack of information about the cuckoos' long migration has hampered the understanding of how to help conserve the birds.
This cuckoo migration map has now revealed, for the first time, exactly where the birds spend the winter and just how brief the time that these so-called British birds actually spend in Britain.
"They're African birds really," said Phil Atkinson, who has taken a leading role in the cuckoo project.
"They evolved in Africa."
Missing in action
Like all migrating animals, they respond to the changing seasons - depending on lush greenery to provide the fruit and the food for insects that they feed on.
This reliance seasonal patterns means that a changing climate could make an already challenging journey impossible.
"All the birds got down to Congo and survived, and it's only on spring migration that we started to lose birds," said Dr Atkinson.
"We lost our first bird, Clement, in Cameroon on the return journey," he told BBC Nature.
"So we think the crunch time is just before they cross the Sahara."
Although the team were sad to lose the birds, Dr Atkinson said that understanding the most challenging parts of a cuckoo's journey - and where they were most likely to die - provided them with "an incredible amount of new and important information".
"These birds move into west Africa, they fatten up as much as they can - enough to fuel their Saharan crossing.
"And if they're not able to do that, I think that's going to be a real pinch point in terms of mortality.
"That's where we need to focus our research effort and conservation action."
The team now plan to continue the project by fitting a group of female cuckoos with the same tracking devices.
"Males and females may well do different things in terms of migration," said Dr Atkinson.
"Males may well be more time-stressed to get back in spring to get a good territory and find females and females might have to stay later to get the last few eggs out.
"As we have seen in the five cuckoos, timing is really important and this may be crucial in determining whether a bird undertakes a migration successfully or not."
Grahame Madge from the RSPB said it was a relief to know that at least some birds were coming back to Britain to carry on future generations.
"The cuckoo is an urgent priority for research," he told BBC Nature.
"This fantastic project is boosting the understanding of this bird so that, hopefully, we can give this bird a future."
