Regular readers of this blog will be aware that Natural England is involved in several initiatives under the Hen Harrier Action Plan, one of which is the brood management trial. Natural England is committed to protecting and conserving hen harriers, and to working in partnership to combat the persecution of these magnificent and iconic birds.
Illegal persecution is the main threat to the recovery of hen harriers in England – as demonstrated by this 2019 study using Natural England satellite-tagging data. The brood management trial aims to establish whether brood management is an effective tool to protect hen harriers from illegal persecution by seeking to change the perception and behaviour of the moorland community.
The aims and background of the trial were described in detail in a blog published in 2020. In short, brood management involves taking hen harrier chicks from the wild and rearing them in captivity. This is expected to lead to reduced predation pressure on red grouse during the breeding season as the adult hen harriers from brood managed nests do not have to find food to feed their young. Once the young harriers taken into captivity have fledged, they are released back into the wild, with the same number of birds being released into the same broad areas of upland habitat that chicks were taken from.
It is a controversial technique, and not everyone agrees that it will have a positive impact. To manage these risks, strict conditions are put on the licences required to carry out this activity.
In 2021, trial interventions were approved at two nests. For 2022, Natural England has issued a further one-year research licence to allow the fifth year of the trial to go ahead, following on from the two-year licences issued in 2018 and 2020. The trial will operate this year in much the same way as in the first four years. There are strict measures in place to safeguard the birds’ welfare and to ensure the local population is not adversely affected.
So far, the results of the trial have been encouraging and we are pleased to have seen an increase in the number of nesting female hen harriers in England during this period, from 14 in 2018 to 31 in 2021. In terms of brood management itself, 21 out of 22 hen harriers taken and reared in captivity have survived to be released - a greater number than would have been expected to fledge successfully in the wild.
A number of the brood managed birds have also gone on to breed successfully in the wild themselves. As of February 2022, 4 of the 7 satellite-tagged birds from the 2021 cohort were still being tracked. We will be working with gamekeepers and partners such as RSPB to keep a close eye on the fortunes of these birds over the coming breeding season and providing further updates later this year.
Following the completion of the trial, a formal assessment and evaluation will be undertaken, with support from a dedicated Scientific Advisory Group. The results of this evaluation will inform a decision on the future role of brood management alongside other techniques aimed at the recovery of hen harriers such as diversionary feeding.
As well as being the licensing authority for the trial, Natural England is also a member of the partnership involved in delivering the trial, with representatives on the Brood Management Trial Project Board. However, as in previous years, a strict separation has been maintained between staff involved in the trial and staff involved in the licence application assessment process.
Natural England licensing staff will monitor the actions taken by the project over the coming months to ensure that all licence conditions are complied with for the remainder of the trial. A further update will be provided later this year when we report on the results of the 2022 breeding season.
A continued close collaboration between public bodies, land managers and conservation organisations, backed up by good science and evidence is vital if we are to see a sustained population increase.
For more information on the work we are doing with hen harriers see my most recent blogs on diversionary feeding, on monitoring, tracking and tagging, and on the actions taken when a tagged bird is lost.