A cuckoo has just completed one of the longest migrations ever recorded by any bird. The cuckoo left its winter home in Zambia in Southern Africa on March the 20th and has arrived at its breeding ground in Mongolia. Ornithologists named the bird Onon after a Mongolian river. They tagged five different cuckoos in Mongolia with microchips last summer to track their migration. The satellite tags monitored the progress of the birds across the Indian Ocean and 16 countries. Onon was the quickest of the five birds to make the return journey from Mongolia to Zambia and back. The ornithologists hailed Onon's feat and described it as being "a mammoth journey".

The tagging of the birds was a joint venture between the Wildlife Science and Conservation Center of Mongolia and the British Trust for Ornithology. It was facilitated by the group Birding Beijing and the Oriental Bird Club. A special blog called the Mongolia Cuckoo Project was set up so bird lovers could track the birds' progress. It reported that Onon arrived home, "as of 15:30 local time on May 27, 2020 after a round trip of about 26,000km, including 27 border crossings involving 16 countries." It called the journey: "Remarkable navigation and endurance." It added: "Onon has no time to waste as he needs to set up his territory, defend it from competing males and mate with as many females as possible."