Can East Anglian cuckoos help shed light on why their numbers are in sharp decline?

PUBLISHED: 10:25 26 June 2019 | UPDATED: 10:38 26 June 2019

Cuckoo Picture: CHRIS KNIGHTS/British Trust for Ornithology

Cuckoo Picture: CHRIS KNIGHTS/British Trust for Ornithology

CHRIS KNIGHTS/British Trust for Ornithology

Cuckoos fitted with tracking devices are part of a project to discover if the hazards they face on their 5,000-mile migration journey are related to their drastic population crash.

Cuckoo named Valentine  Picture: Lee Barber/BTOCuckoo named Valentine Picture: Lee Barber/BTO

The satellite tags have been attached to four birds from Thetford Forest on the Suffolk-Norfolk border, so researchers can follow the cuckoos as they make their way to the Congo rainforest in central Africa, where they winter, and back to the UK again next spring.

Thanks to the continuing miniaturisation of tracking devices, these four cuckoos - which have been named Senan, Valentine, Tennyson and Nussey - are carrying a transmitting backpack that will monitor their every move, feeding back information to British Trust for Ornithology (BTO) scientists, whose headquarters is also in Thetford,

According to the BTO, three of these newly-tagged birds are already on the way, having crossing the Channel and moving into France within the last few days.

A dunnock feeding a juvenile cuckoo  Picture: Alan LeeksA dunnock feeding a juvenile cuckoo Picture: Alan Leeks

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Their journey is full of hazards and will include a crossing of the Mediterranean and a long and arduous flight over the Sahara Desert, before a more leisurely cruise south into the Congo Basin. By following these four cuckoos, and another eight birds that are already part of the project, scientists at the BTO hope to get a fuller picture of the pressures these birds face whilst outside of the UK.

Each year migrating cuckoos face different conditions along the route. The project has been running since 2011, and so far tagged migrating cuckoos have faced severe summer droughts in Spain and Italy, unseasonal hailstorms in spring in Spain, sandstorms in the desert and energy sapping headwinds.

Cuckoo named Senan  Picture: Lee Barber/BTOCuckoo named Senan Picture: Lee Barber/BTO

The Cuckoo is arguably the UK's best known summer visitor but the BTO says since the early 1980s UK cuckoo numbers have dropped by 65%. Scientists are hoping that by relating the performance of the tagged cuckoos to the conditions they face on their journey they may be able to identify what is contributing to their decline.

READ MORE: Why is there a growing number of red kites in Suffolk?

Dr Chris Hewson who is leading the cuckoo study Picture: Mike TomsDr Chris Hewson who is leading the cuckoo study Picture: Mike Toms

Lead scientist on the project, Dr Chris Hewson, said: "Before this project began we had no idea where our Cuckoos spent the winter months, or indeed what the journey to get there entailed. Not only do we now have a very good knowledge of both of these but we are also beginning to understand how changing conditions drive mortality rates.

"By continuing the project with these new birds we will gain more valuable insights into how conditions across the annual cycle, including here in the UK, affect the birds and how this relates to population declines.

"Each year is different and presents its own challenges to the birds."

The progress of the cuckoos can be viewed on the BTO website.

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