Bowie joins BTO's cuckoo class of 2018


As part of its ongoing Common Cuckoo project, the British Trust for Ornithology (BTO) has tagged a further 10 birds this summer, including one named by Chris Packham.

'Bowie', titled by Packham in memory of one of his favourite musicians, was tagged on Tuesday 22 May in the New Forest, Hampshire. On 12 June, his tag transmitted outside the UK for the first time, showing that he was just to the south of Orléans, France, and confirming that his autumn migration had commenced. He is currently north of Montluçon, central France, around 370 miles from his tagging site.

The project was launched in 2011 to help identify what might be driving the decline of Common Cuckoo in the UK, where almost three-quarters of breeding cuckoos have been lost since 1990. The study has revealed the life histories of individual cuckoos to scientists and the public alike, for the first time, uncovering the migration routes taken and possible causes behind the decline.

Since the beginning of the project, 80 cuckoos have been fitted with state-of-the-art satellite tags. Thanks to this, it's now known that the winter months are spent in the Congo rainforest, where they arrive in September and leave, via West Africa, in February. Heading south, the birds use one of two different routes, either through Spain or Italy, yet all winter in the same part of Central Africa – a migration pattern that was new to science when uncovered by the project.

At the moment it is uncertain which route Bowie will take, but the route he chooses may well determine his chances of survival. The survival rates for the two routes are very different, with those migrating via Spain suffering greater mortality. To date all of the cuckoos that have migrated through Spain have come from England, where cuckoos are declining rapidly. All of the cuckoos tagged in Wales and Scotland have taken the Italian route; in Scotland numbers are increasing, while in Wales they are mostly stable.

Dr Chris Hewson, lead scientist on the project, commented: "The route a cuckoo takes on migration seems to play a big part in its chances of survival, and that this could have a big impact on the cuckoo population in different parts of the UK. One of the things we need to understand is what determines the chosen route. Do they come from genetically different populations, for instance? Only time will tell. Right now I have everything crossed for this year's birds, and I'm looking forward to seeing which route they use over the next couple of weeks."

You can follow Bowie's adventures and see which route he takes to the Congo Rainforest by clicking here, while more can be found about the project at www.bto.org/cuckoos.