Summer is winging its way towards Britain

No.:  2018-01
January 2018

We can see summer coming from over 4,000 miles away as the first of BTO’s satellite-tracked Cuckoos begins to head north.

One of BTO’s tracked Cuckoos, known as PJ, was tagged in June 2016 in Suffolk and has since been providing BTO with key knowledge about Cuckoo migration. PJ has now begun to move north, travelling from Angola to Gabon on his way back to Britain, but this move is only a fraction of the journey that he will have to make.

Last year PJ returned to Suffolk on 29th April where he remained throughout his breeding season. On the 24th of June he began his migration to Africa for the winter, taking a more central route from the UK to his most southern point – Angola – avoiding the western route where we have seen more fatalities in other tracked Cuckoos.

PJ is one of only two BTO Cuckoos to have gone as far south as Angola; the information received from the tag identifing this as a new wintering location. In the last 20 years the number of Cuckoos in the UK has decreased by half. To find out why, BTO have been satellite tracking a number of Cuckoos since 2011. This year we are tracking eight different Cuckoos and following their migrations.

In 2009, the Cuckoo was added to the Red List of Birds of Conservation Concern. Although there was a lot of knowledge on the Cuckoo’s breeding behaviour while in the UK, little was known about their migratory behaviour. In order to get some insight into why there may be a drop in numbers of the UK’s Cuckoos BTO decided to use satellite tracking devices to understand their migration routes. We are using this information to find out what is causing the Cuckoo numbers to fall.

Dr Andy Clements, Chief Executive of BTO, says:  “BTO’s migration tracking research is pioneering. Six years into the programme we continue to discover new facts. For example, some of our Cuckoos winter in Angola, previously not well known as a wintering location for UK migrants."

From Angola, PJ has travelled 760km north but there has been little movement from PJ since 27th December 2017. However, this may indicate that he is preparing for his journey back to the UK. When PJ does make his return journey, it is likely that he will head west towards Ivory Coast, following his previous migration routes. This is one of the really great things about our satellite-tracking: you can compare previous years’ journeys and anticipate what the same Cuckoo may do in a different year. It can also help highlight any differences such as changes in the weather, and therefore allow us to understand why individual birds may change their routes.
 
If you would like to follow PJ, please follow this link: www.bto.org/science/migration/tracking-studies/cuckoo-tracking . You will also be able to find seven of the other Cuckoos and follow their journeys as they too begin to head north.

Notes to editors
1. Continuing to tag in future years. Not only does continuing to tag Cuckoos help gain more information, but it also allows us to understand similarities and differences within the Cuckoos we tag.  It also means that we are more likely to have Cuckoos providing us with information over a number of years rather than one or two, this means we can easily look at the differences with weather conditions and other factors that could change each year and how these factors affect the Cuckoos travel.  We can see whether birds that do ‘unusual’ things survive better or worse than others, giving insight into what limits the normal range of the population. 

2. What we have found out so far:

  • Return routes - The Cuckoos followed so far take a different return route to the UK than the one they followed on their outward autumn migration. No matter which route they take south, whether it be via Spain, Italy or further east, all the Cuckoos head to West Africa to make the return crossing over the Sahara to Europe. This information suggests that there are good reasons why Cuckoos visit West Africa on their way back and this is another important aspect of their journey which could prove a pinch point in their success.
  • British Cuckoos - Using data collected in previous years we were able to find out that although the Cuckoos we tag in Britain are referred to by us as ‘British’ Cuckoos, these Cuckoos only spend a small amount of time in Britain. One of the Cuckoos we tagged at the start of the project spent just 15% of his time in Britain, spending most of his time in Africa (47%) and the rest on migration (38%).
  • Mortality - Having followed Cuckoos over a number of years we are beginning to gather a wealth of data about the difficult points during the Cuckoo’s annual cycle. Knowing where the birds are struggling (and dying) will help us understand how their numbers change and hopefully will help to identify the causes of their declines to help inform conservation in the future. 

3. 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 Bangor (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.