Wildlife experts have tracked the 5,000 mile migration journey of five cuckoos, after fitting the birds with satellite trackers in bird backpacks.
Scientists from the British Trust for Ornithology caught and fitted the birds with the tracking devices in June to find out where they like to live.
They're worried that cuckoo numbers in the UK have halved in 15 years.
The trackers showed the birds flew off from the same part of East Anglia, but spread out over 1,860 miles of Africa.
Four of the birds have already crossed the Sahara; two are in southern Chad, one is in northern Nigeria and the fourth one is in Burkina Faso.
One cuckoo is lagging slightly behind the rest and has made it as far as Morocco.
Cuckoos only live in the UK for part of the year, before flying to warmer countries. But in recent years fewer and fewer birds have been making the return trip to the UK and experts want to find out why.
This is the first time cuckoos have been tracked and it's hoped the results will help to solve the mystery of why their numbers are falling.
Now the birds have reached Africa, experts will be watching to see what happens to them before they try to return to the UK.