An unexpected journey
An unexpected journey11 Sep 2020
For the last two years we have been following our Suffolk Cuckoo Carlton II on its annual migration to central Africa – what it did on 1 September took us all by surprise!
The male Cuckoo was fitted with a satellite tag during the spring of 2018 and has been providing us with information on his movements ever since. This year he left Carlton Marshes, Suffolk, on 2 July, next stop northern Spain. Nearly two months later, on the evening of 1 September, he was finally ready to begin the next leg of his journey from Galicia, the north-western tip of Spain, heading for tropical West Africa.
Whether encouraged by light winds or sensing opportunity, he set off from the coast of Spain, where strong northerly winds helped him on his way south over the Atlantic. The following evening, when his satellite tag powered up again, he was found to be more than 100 miles off the south-western coast of Morocco, close to the border with Western Sahara, at which point the tag powered down again.
British cuckoos usually minimise the distance they travel over water, so it was an anxious wait for BTO staff to see whether he had made landfall when the tag next came back online. On the evening of the 3 September we got our answer – he was making his way south across the desert from Western Sahara into Mauritania. By the early morning of 6 September Carlton II had successfully completed the desert crossing, having flown 1,000 miles across the Atlantic and another 850 miles across the desert.
Although British cuckoos rarely make long sea crossings, the species is perfectly capable of doing so, as illustrated by the birds we have tracked from Eastern Asia, which cross the Indian Ocean twice a year. Flying over the desert or ocean may make little difference to a bird migrating thousands of metres above the earth’s surface – what matters is the reliability of winds helping them along their way. So what appears to us to be an incredibly dangerous migratory feat is straightforward for a Cuckoo – the catch is it has to judge conditions just right so as not to end up in trouble!Dr Chris Hewson, lead scientist
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