During May, three Cuckoos were fitted with satellite tags in Sherwood Forest by the British Trust for Ornithology (BTO) to gain information on their movements once they leave the UK.
During the last week they have all left Nottinghamshire and are now well on their way to the rainforest.
Two of the Cuckoos were caught at Sherwood Pines and the third bird, named Dudley, at Shirebrook.
Dudley is the first Sherwood-tagged Cuckoo to reach Africa, and the first to successfully cross the Sahara Desert; he is currently on the edge of the rainforest, in eastern Nigeria.
Unnamed Cuckoo, 134955 is in Morocco, just east of Marrakesh, with the other unnamed bird, 134957, being in Belgium, close to the border with the Netherlands and Luxembourg.
During the next couple of weeks all of them will make their way south but each bird will take its own route, all crossing the Mediterranean Sea and the Sahara Desert.
They might not all make it to the wintering area in the Congo Rainforest, the crossing of the desert is extremely tough and can take its toll.
The information that they provide as they make their way there will be vital in helping scientists at the BTO understand what might be driving the decline of the British Cuckoo; we have lost almost three-quarters of our breeding Cuckoos during the last twenty-five years.
Erin McDaid, of Nottinghamshire Wildlife Trust, said: “We are delighted to be supporting the BTO in their efforts to understand more about the enigmatic Cuckoo.
“Our staff were involved in the work to fit the birds with the tags and we hope to use the experience gained in other species monitoring projects in the future. We are following the progress of the birds from Sherwood Forest with great interest and very much hope they all return next year.”