British Cuckoo completes 22,000 mile odyssey in record time

24 Apr 2020 | No. 2020-12

 A Cuckoo called Carlton II has just arrived back in England having spent the last ten months travelling to and from the Congo rainforest, becoming the first of the BTO’s satellite tracked cuckoos to return to this country in 2020. 

Aided by favourable southerly winds, he completed the last leg of his mammoth journey in record time, Ivory Coast to southern England in seven days. In doing so, he leap-frogged two other tracked cuckoos, named PJ and Senan, currently stopping over in Spain and North Africa respectively.

Carlton II was fitted with a high-tech satellite tag in May 2018, by scientists from the British Trust for Ornithology at SWT Carlton Marshes, Suffolk, to allow them to follow his every move. We have lost almost three-quarters of our breeding Cuckoos during the last 25 years and, as Cuckoos spend more time outside of the UK that they do in it, it is vital to understand where they go, the journey they take to get there, and any pressures they face that might be contributing to their decline.

Carlton II spends the summers in Suffolk and the winters in Gabon, Central Africa, and travels over 5,500 miles between the two, dodging many hazards, such as high winds, sand and hailstorms, ferocious thunderstorms, drought and lengthy sea-crossings. Since having his tag fitted Carlton II has flown over 22,000 miles on his migration.

Dr Chris Hewson, BTO lead scientist on the project, “It is great to see Carlton II getting back to the UK so quickly. Taking just a week to cover more than three thousand miles from Liberia to Berkshire is an awesome feat and something even  swifts don’t manage. This shows us just how quickly these harbingers of spring can get here from tropical Africa when conditions for their journey are good It’s a journey so full of hazards that it’s always a relief when they get back,  no matter how fast or slow. These Cuckoos have taught us so much about their lives, giving answers but also raising more questions as to what might be behind their decline.”
Anyone can watch the Cuckoos as they make their incredible journeys at

Contact Details

Paul Stancliffe
(BTO Media Manager)
Mobile: 07585440910
Email: press [at] ()

Images are available for use alongside this News Release. Please contact images [at] quoting reference 2020-11 if you have any queries.

Notes to editors
BTO Cuckoo Tracking Project 
It's well known that we have lost over half of our breeding cuckoos during the last twenty-five years. Populations of many UK breeding migrant species are declining, however, there is little known about the mechanisms of these declines.
Climate change is causing the timings of the spring season to change and there is evidence that many migrant species are not advancing their arrival times sufficiently to track the earlier spring. There is also some suggestion from previous studies that there are constraints in the migration timing of species wintering in or beyond the humid zone in Africa.
We also know from the BTO/JNCC/RSPB Breeding Bird Survey that Cuckoos are doing better in some areas of the country than in others, with the decline in England (68%) being greater than in Scotland and Wales, but why are they are declining at the rate they are?
Clearly we need to understand all aspects of the Cuckoo’s annual cycle before we can begin to suggest what might be driving the decline. Read more here

The BTO is the UK's leading bird research charity. A growing membership and up to 60,000 volunteer birdwatchers contribute to the BTO's surveys, collecting information that underpins conservation action in the UK. The BTO maintains a staff of 100 at its offices in Thetford, Stirling, Bangor (Wales) and Belfast (Northern Ireland), who analyse and publicise the results of surveys and projects. The BTO's work is funded by BTO supporters, government, trusts, industry and conservation organisations.

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