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JAC is named in loving memory of Professor Jenny Clack, a world-class palaeontologist, widely acknowledged as the leading authority on the evolution of land vertebrates from fish. The name JAC was chosen by Jenny’s husband Rob who said: “It seemed appropriate I should contribute to this important scientific study of Cuckoos in memory of a top-class scientist, whom I adored.”

JAC the Cuckoo
Tuesday, June 1, 2021 - 05:00
Tagging Location:
World's End, Llangollen, Denbighshire
Age when found:
Satellite Tag No.:
Wing Length (mm):

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JAC's journey from 02 May 2023 to 26 February 2024

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JAC's movements

09 Jun 2023 - The end of the road for Cuckoo JAC

We are very sad to report that we have heard the last from Cuckoo JAC.

JAC, named in loving memory of Professor Jenny Clack, was tagged at World’s End near Llangollen on 1 June 2021. Since then we have had the privilege of tracking him over two full migration cycles from Wales to Africa and back.

His route south across the Sahara took him via Algeria and Mali to the Sahelian areas of Burkina Faso or Niger. He then spent some time in northern Nigeria before heading on to the Congo. On his return migration north, he visited West Africa where he stopped in Ivory Coast in 2022 and Guinea in 2023, arriving back in Llangollen around the end of April each year. 

The diagnostic data received from his tag shows the recorded temperature dropping and this, along with the fact that he appears to have been stationary for quite a while, suggests that he has perished (rather than there being a tag failure).

He has made a very valuable contribution to our growing knowledge of Cuckoo ecology and we will miss reporting on his movements.  

24 Apr 2023 - JAC is back!

We are pleased to report that JAC completed his migration back to his breeding grounds over the weekend. Over the last three months he has flown 8,270km (5,138 miles) on his migration north and has arrived at his breeding grounds approximately one week earlier than last year. In 2021 he departed on 23 June and in 2022 he left on on 20 June so we expect him to stay in the World's End area for approximately two months before heading off on his return migration to the Congo. 

21 Apr 2023 - JAC reaches northern France

New updates received from JAC's tag on Wednesday (19 April) show that he had flown 923km (574 miles) north from his last location in eastern Spain to northern Brittany. At 21:42 on Wednesday 19 April he was just west of the town of Saint-Gonnery. Where will he be when we receive the next update?

30 Mar 2023 - JAC pushes north through Spain

New updates received late last night show that JAV has flown a further 515km (320 miles) north east from his last location in Andalusia. He is now close to the village of Graja de Campalbo in the province of Cuenca, Castilla-La Mancha. 

28 Mar 2023 - JAC crosses the Sahara

We predicted, based on data from last year, that Ellis would be the first of our tagged Cuckoos to cross the Sahara this year. Last year he crossed on 28 March, while JAC waited until 7 April and Victor II lingered until 14 April. New updates received last night show that JAC has not only crossed the Sahara but continued on into Spain. He has flown 3,047km (1,893 miles) north since our last update, taking him from south eastern Guinea over the Sahara and the Strait of Gibraltar into southern Spain. He is now close to the town of Gaucín in the mountains of Andalusia in Málaga. Last year he stayed in southern Spain until 26 April when he moved north again, arriving back in Llangollen on 29 April. It'll be interesting to see whether he takes a break in Spain this year before embarking on the next stage of his migration.

Past updates from Jac

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© British Trust for Ornithology.