The five cuckoos are carrying satellite tags — which look like miniature backpacks — fitted before they began their migration from Norfolk, in eastern England, in July bound for Africa’s southern nations. Information collected on their route is helping experts learn more about the impact of population growth and climate change on the birds’ habitats.
For the first time, scientists are examining where and when the migrating cuckoos stop off on their journey through Africa, hoping to understand more about why fewer and fewer birds are able to make the return trip the following year.
Graham Appleton, a spokesman for the British Trust for Ornithology, which is carrying out the research work, said the number of cuckoos in Britain has fallen by about 60% over the last 25 years.
Cuckoos traditionally arrive in Britain in April and migrate again around June or July.
Appleton said that the five birds were captured in large mesh nets — lured with a recording of a female bubbling call — and fitted with the 5 gram, solar-powered satellite tags. “The tags turn on for about 10 hours every two days, and relay information about where a bird is. That will tell us more about the routes the cuckoos take to their wintering areas and where they stop off along the way,” he said.
Once they know more about the cuckoos’ favoured stops, scientists plan to work with colleagues in those countries to examine the possible reasons behind the fall in numbers of migrating birds.
“We’ll be looking for ways to work with local partners in those areas to look at the impact of population growth on biodiversity and on habitats,” Appleton said.
Two of the cuckoos’ are now in Chad, with other birds in Burkina Faso and Nigeria. A fifth bird, named Lyster by scientists, remained in Britain until late July, and was tracked on Thursday to the coast of Morocco, about 13 miles (20km) from Casablanca.
“The satellite tags should last for at least a year, so we also hope to track the birds as they make their return journey to Britain,” said Appleton.
Richard Grimmett, director of conservation at Birdlife International, said: “In some cases it is necessary to gain a better understanding of what is driving these declines, but for others we already know enough to be able to target the principle causes. These birds urgently need our help.”