But to follow a cuckoo, you must first seduce it.
The common cuckoo is by reputation a cynical freeloader.
Mothers outsource parenting by laying their eggs in the nests of smaller birds, and the birds live on grubs, caterpillars and similar soft morsels. British and Chinese bird groups decided to study two cuckoo subspecies found near Beijing, because their winter getaways were a puzzle. In an online poll for the project, nearly half the respondents guessed they went somewhere in Southeast Asia.
“We really didn’t know for sure,” said Yu Fang, a coffee importer, a prominent member of the Beijing bird-watching community and a volunteer on the project.
“We knew that the cuckoos breed around here. But where do they go over winter? I guessed it was India,” Mr. Yu said. “I’ve been bird-watching in India, and they are often spotted there. I thought that’s where they stopped.”
To tag the birds, the team set up soft, barely visible nets in May to safely catch the birds. A stuffed female cuckoo was attached to a tree or bush, and a recording of the bird’s come-hither mating call was played out.
They responded lustily.
“The male cuckoos just can’t resist. They come in from a long way,” said Mr. Townshend, who works as a consultant on a variety of environmental projects. Unexpectedly, female cuckoos also came to the party, seemingly jealous about an apparent rival in their patch, he said.
After excluding birds too light to safely carry the sensors, the team attached solar-powered tags weighing 0.16 ounces to the backs of five birds, each weighing around 3.5 ounces, and freed them into the wild, where satellites followed the signals from their tags. Such technology has revolutionized the study of migratory birds since the 1990s.
“Tracking technology has ushered in a new age of exploration,” Mr. Hewson said.
But the project was also intended to raise awareness of wild birds and their needs, especially in China, where expanding cities, pollution and commercial capture with huge nets threaten the creatures. Schools in Beijing for local and foreign children gave the birds their names. As well as Flappy and Skybomb, there was Hope, Zigui and Meng Zhi Juan, a poetic Chinese phrase meaning “dream bird.”
The wait began. As blazing summer arrived, time approached for the birds to begin their migration. But not all could. Cuckoos often have brief lives. The trackers ran out of contact with Hope after she flew north to Russia, possibly dying or losing her tag. And Zigui’s signal stopped near Beijing, where he probably perished.
Then in early August, Flappy struck south, followed weeks later by Skybomb and then Meng Zhi Juan. Each day, Mr. Townshend checked the satellite data to see whether any other birds were on the move. Their journeys, chronicled on Twitter, drew in more and more fans, including me.
By mid-September, Skybomb and Flappy were in India. That more or less ruled out the idea that they were headed to Southeast Asia, and they appeared likely to head west. But by which route?
The first answer came in late October. Skybomb struck out boldly from central India and, without stopping, headed across the northern Indian Ocean, apparently aiming to reach Africa in one lunge. It was a breathtaking gambit for one of these small creatures.
“When Skybomb set out across the ocean, it was like, Whoa! He’s going for it,” Mr. Townshend said. Skybomb had fattened on grubs, but Africa was thousands of miles away without the prospect of a stop or meal in between.
“It was a real celebratory moment,” Mr. Townshend said. “But fingers were crossed that he was going to make it across the ocean.”
There was an implacable logic in the cuckoos’ seeming folly, said Mr. Hewson, who had guessed that they would go to Africa. They stopped over in India when rains had still left plenty of food there and waited for the monsoon winds to make a drastic turnaround, so the birds could fly onward with the help of the breeze. Cuckoos that summer in Europe also head to Africa to avoid the winter.
Skybomb plowed on. Flying at roughly 2,600 feet above the sea, he held to an astonishingly straight path, apparently calibrating for shifts in the wind and conditions. By the second day, he was halfway across. After a third day, the east coast of Africa, and food and rest, beckoned.
For much of the flight, Skybomb was helped by tailwinds. But as land approached, crosswinds and then a front-on headwind struck. It was a moderate breeze, but maybe enough to exhaust a cuckoo after days without stopping.
On Oct. 31, Mr. Townshend announced on Twitter that Skybomb “is in Africa!”
Sixty-four days after he had begun his migration, the cuckoo had reached the coast of Somalia about an hour after dusk. He had flown nonstop for 2,300 miles from central India. “What a bird!” Mr. Townshend declared.
But even then, Skybomb was not done. Right way, he flew for another 190 miles until he reached an area where recent rains would have brought a proliferation of caterpillars and grubs to eat. Somehow, he knew where to follow the rain.
The other birds began their long flights later than Skybomb. Flappy took a more cautious path, crossing the Arabian Sea from India to Oman. That made for a shorter flight over water, but also meant she hit land in northern Africa, farther from the lusher terrain to the south. By Friday, Meng Zhi Juan had jumped to just a few miles from the Indian coast and appeared poised to follow Skybomb’s swoop across the ocean to Somalia or thereabouts.
The birds appear likely to edge south in Africa, following the rains. If they survive, they are expected to arrive back in Beijing in May.
Mr. Townshend and his colleagues hope to follow more cuckoos next year, if they attract enough donations to pay for the tags and satellite services. More knowledge will help protect the areas they need to stop in.
“They’re birds that are shared by China, India, Myanmar, Somalia and wherever else they go,” Mr. Townshend said. “With that comes a shared responsibility to protect them.”