By Tom Grose, Investigations Officer

Satellite tags have been fantastic for helping to shed light on the lives of a wide variety of animals around the world. One outcome from their use on birds of prey in the UK has highlighted the scale of persecution facing some of these species. A peer-reviewed paper utilising the tagging data of 58 Natural England tagged Hen Harriers was published in 2019. The science showed what was long anecdotally suspected: Hen Harriers were 10 times more likely to die or disappear within land managed for grouse shooting compared to areas that weren’t. 72% of the tagged harriers in that study were either confirmed, or considered very likely to have been, illegally killed.  

Unsurprisingly, intelligence suggests that these small, lightweight devices are not popular with those carrying out the killing. The case of a Golden Eagle tag which was wrapped in lead and thrown into a river shows the lengths that criminals will go to avoid detection. It has often been suspected that Hen Harriers and their tags have been subject to similar tactics (see the story of Bronwyn).  

The RSPB has been fitting satellite tags to hen harriers for many years. The work is carried out to extremely high standards by trained, BTO-accredited experts. In the summer of 2021, the RSPB fitted a satellite tag to a male hen harrier chick on United Utilities land in the Forest of Bowland. It was fantastic to see this bird – named Anu – spread its wings as it explored further afield, eventually reaching the edge of the Peak District in South Yorkshire where it spent the winter. Our team were able to observe him interacting with a female Hen Harrier, sparking hopes that he might stay to breed in that part of the world. Sadly, those hopes were dashed. 

On the night of 10 February 2022 Anu roosted near Upper Midhope in South Yorkshire. The area was known to our team as a spot where other harriers have roosted in previous years and was clearly attractive to them. It is also land managed for driven grouse shooting. Hen Harriers roost on the ground often amongst heather or long grasses like rush, flying into the roost at dusk to settle in for the night. The tag data confirmed that Anu was alive in the early hours of 11 February, but strangely that the bird had been unexpectedly active during the night: a time when Hen Harriers do not usually fly and we would expect it to be roosting and still. 

The next signal from the tag on 11 February gave cause for concern. The data indicated that Anu was dead. Further location data indicated bird/tag was now approximately 9Km away to the east at Wharncliffe Chase. After a thorough search using specialist equipment in wet conditions, we found no sign of the bird or tag, despite the tag continuing to transmit from the same location.  

We returned for another intensive search and eventually found the tag. There was no sign of the body, not even a scattered feather indicating it may have been removed by a scavenging animal. Worryingly, and crucially, the harness which securely fastens the tag to the harrier appeared to have been severed. We reported our concerns to South Yorkshire Police who took the tag for forensic analysis. They agreed that Anu’s disappearance was now suspicious. 

The next step was to comb the roost area near Upper Midhope where Anu was last known to have been alive. A large search party comprised of the police, the National Wildlife Crime Unit and RSPB Investigations staff found no Hen Harrier feathers or remains. A public appeal for information was swiftly issued. Police enquiries continued while we waited for the forensic tests to be carried out on the tag and harness. 

When the police received the initial results back from the lab in May, it confirmed what we had feared and suspected. The results indicated that the harness had “been cut….rather than having been severed as a result of any animal activity”. In the opinion of the examiner there was no indication on the tag or harness that it had been removed by an animal. This was now officially a criminal investigation.  

Anu's tag, showing the cut straps

Despite the best efforts of the police, further enquiries were unsuccessful in establishing those involved. As raptor persecution often occurs in isolated rural locations, narrowing the enquiry down to a single suspect is often very challenging. It seems probable that Anu met the same fate as many other Hen Harriers, and that the culprit tried to cover their tracks by removing the tag from the bird’s body and relocating it away from the crime scene.  

Instead of going on to rear chicks of his own, Anu had become another dead Hen Harrier statistic, waiting to be collated and published in yet more science clearly indicating the impact of human persecution on this species. 

With only a fraction of the UK Hen Harrier population carrying tags, you can’t help wonder what is happening to those other, untagged birds. Until human and criminal persecution ends, this species will continue to struggle. That’s why the RSPB is urging the UK Government to implement licensing for driven grouse shooting, as is due to happen in Scotland this year. It’s clear that we need meaningful change, and a meaningful deterrent to illegal killing, otherwise this depressing narrative will only continue.  

The RSPB would like to thank South Yorkshire Police and the National Wildlife Crime Unit for their hard work on this case.