Cloud cuckoo land? How one bird's epic migration stunned scientists

When Onon the common cuckoo took off from Mongolia last June no one expected him to make a 26,000km round trip to southern Africa

When Onon took off above the rolling hills of the Khurkh valley in Mongolia last June, researchers had no idea if they would see him alive again. Along with one oriental cuckoo and three other common cuckoos, each fitted with a tiny tracking device, he was about to embark on an epic journey to southern Africa.

Last month, he was the only bird to return safely with his tracker intact.