Five cuckoos put on their backpacks for a big adventure

Clement is somewhere south of Paris and Chris has flapped his way to Battle in Sussex. Both appear to be heading back to sub-Saharan Africa, as inexperienced young adult males often do.

Next summer, when they’ve got the hang of claiming territory and mating techniques, they will stay in Britain for longer and breed more successfully. In the meantime, ornithologists in the UK will be able to track the movements of the two cuckoos – and three others – using tiny electronic tags and global positioning via satellite technology to pinpoint their whereabouts over the next year. They’ll use the tracking data to try and figure out why the population of the species in this country has dwindled by 65 per cent in 25 years.

When was the last time you heard a cuckoo’s song, that welcome sound telling you summer is on its way or already here, in full flower? Hordes of concerned bird lovers have been calling the British Trust for Ornithology, saying they’ve not heard a cuckoo in years. The reports are sad, but no surprise to the scientists who have been watching successive surveys and pulling out all of the stops to try and understand the reasons behind the alarming disappearance of one of our best-loved birds.

“The European cuckoo is the iconic sound of summer, and it is the only species of cuckoo that breeds in the UK,” says Paul Stancliffe, an ornithologist with the BTO. “We’re a scientific organisation that monitors breeding trends across all species, with some of our surveys running since the 1920s. The cuckoo is a migrant species that winters in Africa then comes to breed in Britain in early to mid-April. It doesn’t brood its own eggs, but lays them in a host bird’s nest, commonly that of the reed warbler. The nest will already contain some reed warbler eggs, but the cuckoos hatch sooner and get rid of the other eggs, and are then adopted and fed by the host mother. It helps that the young cuckoo’s begging call sounds very like that of the young reed warbler, and it has the same tongue spots.”

The mother cuckoo is already on her way back to Africa by the time her babies are being tended by another female, and the youngsters follow in September, when they are strong enough to make the journey. Scientists who are exercised by the rapid decline in the cuckoo population here are looking at all of the possible drivers of the phenomenon, including habitat and the movements and habits of the host species. So far no joy.

“We know a lot about what happens to cuckoos when they are in the UK and haven’t found the answer,” says Stancliffe. “Once they head off back to Africa for the winter we lose sight of them and factors that might explain what’s going on. That’s why we’ve taken five male cuckoos named Chris, Clement, Martin, Lyster, and Kasper, and attached electronic tags to them that are like little five-gram backpacks with soft loops that fit over their wings. Using satellite technology, the backpack or tag means we can track the birds for the next year, updating their movements every 24 hours.”

The BOT experts know that the birds have to stop en route to their winter feeding grounds, and it’s hoped that the technology will enable them not only to track the precise movements of the birds, including exactly where they stop on their journey back and forth and for how long, but also to marry up the data with information on weather at every point and agricultural information in each place they rest and feed. Each bird lays down huge fat stores before journeying back to Africa, but those stores are exhausted along the way and have to be topped-up. It’s known that the birds’ route to Africa takes them across the Channel and south-east towards the Italian Alps and the Mediterranean. Beyond there, things are hazy.

Tracking the birds is a new endeavour for the BTO, and the five cuckoos’ progress can be followed via the trust’s website, where each of the travellers has his own blog.

The charity hopes this new investigation harnessing the tiny tags and technology often used to track much larger objects (each cuckoo weighs 100g-140g) will enthuse people enough to donate something towards the thousands of pounds that will be needed to monitor “the boys” over the next 12 months.

The three who are still mooching around breeding sites on the Norfolk Broads should soon be on their way, little realising that they are feathered pioneers of the 21st century.

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