Suffolk Cuckoo's Atlantic Odyssey

For the past two years, researchers from the British Trust for Ornithology (BTO) have tracked a Suffolk cuckoo on its annual migration to Central Africa – what it did on September 1st surprised everyone!

The male cuckoo, called “Carlton II” by the team, was equipped with a satellite tag in spring 2018 and has been informing BTO scientists about its movements ever since. That year he left Carlton Marshes, Suffolk, on July 2nd, the next stop in northern Spain. Almost two months later, on the evening of September 1st, he was finally ready to begin the next leg of his journey from Galicia, the north-western tip of Spain, towards tropical West Africa.

Whether encouraged by light winds or seeing opportunities, he set out from the Spanish coast, where strong northerly winds helped him on his way south across the Atlantic. The following evening, when his day was turned back on (his batteries were charged by small solar panels), he was more than 100 miles off the southwest coast of Morocco near the Western Sahara border.

Common Cuckoo, Copyright Andy Adcock, from the Surfbirds Galleries

British cuckoos usually minimize the distance they travel over water. Hence, it was an anxious wait for BTO staff to see if it had landed the next time the day went online. They received their answer on the evening of September 3rd – he was on his way south across the desert from Western Sahara to Mauritania. By early morning of September 6, Carlton II had successfully completed the desert crossing after flying 1,000 miles across the Atlantic and another 850 miles through the desert.

Dr. Chris Hewson, lead scientist on the BTO project, said, “Although British cuckoos rarely make long crossings, the species is capable of doing so, as demonstrated by the birds from East Asia that cross the Indian ocean twice a year. Flying over the desert or the ocean can make little difference to a bird migrating thousands of feet above the surface of the earth. The decisive factor is the reliability of the winch that helps you on your way. What seems to us to be an incredibly dangerous migratory feat is straightforward for a cuckoo – the catch is that it has to assess the conditions just right in order not to get into trouble! “

We have lost more than half of our breeding cuckoos in the past 25 years, and the BTO project aims to understand what could be driving this decline.

You can follow the cuckoos on their way to their wintering areas in the Congo https://bto.us13.list-manage.com/track/click?u=b0c8b4689232cb8e38fb5af91&id=3fb04e9f0a&e=aa7019a765