Hen Harrier Trial Report Reveals Fate of 36 Unaccounted Birds

The final evaluation report for the Hen Harrier Brood Management Trial hit the public domain in July 2026. It contains a line that sticks in the craw. Out of 39 birds fitted with satellite tags, only three are confirmed alive. The report explicitly states there is no current evidence of survival for the other 36. It sits quietly in a dense document, yet it carries the weight of a decade of conservation effort.

For years, the narrative has been one of cautious optimism. The trial aimed to reduce conflict between raptor hunters and farmers by managing breeding colonies. If it worked, persecution should have dropped. Survival should have risen. But the data suggests a much more complicated reality. The birds are gone, and the reasons for their disappearance remain largely unknown.

The Numbers That Do Not Add Up

Between 2019 and 2023, a total of 59 chicks were taken into captivity. Of those, 58 were released back into the wild. This was a significant logistical undertaking. It required capturing young birds, housing them, and fitting them with technology before setting them free. The goal was clear. Track their movements. Monitor their health. Understand their behavior.

The tracking equipment was the key to this experiment. Satellite tags were designed to provide a continuous feed of data. If a bird died, the signal would stop. If it moved, the location would update. This allowed researchers to build a map of survival. It was supposed to be the definitive record of what happened to these specific individuals.

However, the final tally is stark. At the end of the trial period in December 2024, only three birds were still actively being tracked. The remaining 36 had vanished from the records. There is no live signal. There is no confirmed location. They are simply absent from the data.

Two Confirmed Deaths

Among the 36 birds with no current evidence of survival, two have been identified as dead. These are not assumptions. They are confirmed cases. The Raptor Persecution UK organization has included them in their running tally of missing or killed Hen Harriers. This distinction is crucial. It means these birds did not simply disappear into the wild.

The first was identified as R2-F2-20. It was part of the 2020 brood. The second was R3-F1-22, from the 2022 cohort. Both birds had spent the winter of 2022 at the same roost in the North Pennines. This geographic overlap suggests a shared environment, or perhaps a shared threat.

The post-mortem examinations revealed something disturbing. Shotgun pellets were found in both birds. This is direct evidence of persecution. It is not a natural death. It is not a predator taking prey. It is a human act. The presence of these pellets confirms that the threat the trial was designed to mitigate was still active.

The Data Gap

The remaining 34 birds are the real puzzle. They are not confirmed dead, but they are not confirmed alive. Their signals have stopped. Their locations are unknown. In the world of wildlife tracking, this is a gray area. It could mean the batteries died. It could mean the tags failed. Or it could mean the birds were killed.

Natural England published the details of these two confirmed deaths on 18 December 2024. This was after the relevant police investigations had concluded. This timing is important. It suggests that the authorities had enough evidence to close those specific cases. But it does not explain the other 34 birds.

The lack of data for the majority of the tagged group is a significant gap. Without live signals, it is impossible to determine cause of death. It is impossible to map their final movements. It is impossible to know if they were poached, or if they simply perished from natural causes. This uncertainty undermines the core purpose of the tracking.

What the Trial Was Meant to Prove

The theory behind the trial was straightforward. If brood management reduced conflict with grouse shooting interests, persecution should decrease. Survival should improve. More birds should breed in the wild. It was a logical chain of cause and effect. Manage the population. Reduce the pressure. Watch the numbers rise.

But the reality is messier. The trial ended in 2024. The final evaluation was published in 2026. In that time, the population has not shown the dramatic recovery the trial hoped for. The birds are still scarce. They are still vulnerable. The data does not support the idea that the trial was a clear success.

This does not mean the trial was a failure. It means it was incomplete. The data is missing. The causes of death are unknown for most of the birds. The trial has raised more questions than it has answered. It has highlighted the difficulty of monitoring a rare and persecuted species in a hostile landscape.

The Unanswered Questions

The most pressing question is simple. What happened to the 58 birds? We know two were shot. We know three are alive. We know nothing about the other 53. This is a significant gap in our understanding. It is a gap that needs to be filled.

The trial has ended, but the investigation should not. The data needs to be analyzed. The causes of death need to be determined. The impact of the trial on the wider population needs to be assessed. This is not just an academic exercise. It is a matter of conservation policy.

If we do not understand why these birds died, we cannot prevent it from happening again. The Hen Harrier is still one of Britain's most persecuted birds. The trial was a step forward, but it is not the end. The questions remain. The data is incomplete. The mystery is unsolved.