Avian air miles
In the last two decades, Britain has lost almost half of its cuckoo population, and numbers are continuing to decline steadily. However, conservation of the cuckoo has been hampered by a lack of information surrounding the cuckoo’s long migration to and from its breeding grounds.
In an effort to understand more about this extraordinary species, the British Trust for Ornithology (BTO) fitted five male cuckoos with small satellite tags in May last year. It was hoped that following these avian adventurers would help scientists to discover why fewer and fewer cuckoos are returning to the UK each year.
Two of the birds, named Lyster and Chris, are helping scientists to unravel the mystery of the cuckoo’s migration. After a remarkably long journey – Lyster clocked an incredible 10,000 miles in total – both birds arrived back in the UK last week. Lyster was spotted in the Norfolk Broads on Tuesday, just 10 miles from where he was tagged last May.
“It’s just fantastic,” said Dr Phil Atkinson, head of international research at the BTO. “We know where he’s been, we know the routes he’s taken and now he’s back in the Broads.”
By tracking Lyster and Chris, scientists were able to create a migration map, which revealed exactly where the cuckoos spent the winter. The map also highlighted how little time cuckoos, which are often thought of as British birds, spend in Britain.
“They’re African birds, really,” said Phil Atkinson. “They evolved in Africa.”
Missing on migration
Unfortunately, three of the birds didn’t make it back to Britain. As with all migratory species, cuckoos respond to the changing seasons, and rely on the presence of lush vegetation to provide food for the insects that they feed on. This means that a changing climate could create additional barriers along their already arduous journey.
“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. So we think the crunch time is just before they cross the Sahara.”
The loss of the birds was a blow to the research team. However, the new information gleaned from this event regarding the most challenging parts of a cuckoo’s migration could actually help with the conservation of the species.
“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,” said Dr Atkinson. “That’s where we need to focus our research effort and conservation action.”
Following the success of the tagged males, the team now plans to continue its research by fitting female cuckoos with the same devices and tracking their progress. The team is keen to find out if migration patterns, both in terms of route and timing, are different between males and females.
Male cuckoos may need to return to the UK earlier than females in order to ensure they occupy a good territory and find females to mate with, while the females may have to stay in the UK later than the males, to lay the last clutch of the season.
“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,” said Dr Atkinson.
Grahame Madge, of the RSPB, praised the tagging study, and expressed relief that some cuckoos were successfully completing their migrations and returning to Britain to breed.
“The cuckoo is an urgent priority for research,” he said. “This fantastic project is boosting the understanding of this bird so that, hopefully, we can give this bird a future.”
Read more on this story at BBC – Tagged cuckoos complete migration and return to the UK.
Learn more about the cuckoo on ARKive.
Kathryn Pintus, ARKive Species Text Author