Unfortunately, we have received no further locations for Boris. We are unable to draw any conclusions as to what might have happened. The new 2g tags have not worked well on the Cuckoos and his loss could well be down to tag failure but we don't really know. We are unlikely to hear from him again, even though we have occasionally lost Cuckoos for several months for them to pop-up again when they begin to move. Boris should now be in an area where the tag should be getting plenty of sunlight to charge the battery. If the tag was going to burst into life it really should have done by now.

In 2017, we have been trialling the very latest satellite tracking technology - this year’s cohort were tagged with 2g tags from Microwave Telemetry.

We have, unfortunately, ‘lost’ contact with most of them already. It would seem that the smaller size of the new tag allows the solar panel, used to recharge the tiny battery, to become shaded by feathers, resulting in much less efficient charging of the battery, and consequently lower contact with the tag. Although some may have died, the lack of transmissions from the tags makes it impossible to assess this and in all cases, there were no indications that the birds were in trouble when we last heard from their tags.

This is exacerbated during the winter months by the birds spending more time under the canopy in the Congo rainforest. We don’t know how the batteries will fare when the birds begin their northward migration back to the UK. On leaving the rainforest the tags should receive more sunlight which might be enough to overcome feather shading, and if this happens some of the ‘lost birds’ could pop-up again in February or March, but it is possible that the prolonged shading will have caused irreversible damage to the much smaller batteries in the 2g model. We all have our fingers crossed.

As we move forward we are continuously looking for effective ways to continue gathering this important data for Cuckoos, and other species, to benefit our knowledge and ultimately wildlife conservation. We hope that next year we will be able to track a cohort of cuckoos without these issues arising. 

A new signal from Boris's tag on 18 September places him in Senegal roughly 600km (350 miles) south west from his last location in Mauritania.  He is just south of the Senegal River and close to the town of Dagana. 

A poor signal on 21 August placed Boris in southern Mauritania, roughly 1140km (700 miles) further south than his previous position in Algeria and not far from completing his Sahara crossing. We would have expected him to continue at least as far as Mali where conditions will likely be better for feeding up after his long journey but so far no further locations have been received to reveal that he has moved on and completed his desert crossing.  We are a little concerned about this but will have to wait for more information.