Irish Hen Harrier Winter Survey (ICYMI)

Irish Raptor Study Group

Twitter @IrishRaptorSG @ihhws
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This Blog had a lot of interest when posted on 13/3/21.
In Case You Missed It (ICYMI) I have re-posted it again today!
Thank you for your support

The Irish Hen Harrier Winter Survey is one of Ireland’s longest running ecological studies. Ryan Wilson-Parr, provides here an overview, not only providing high-quality information to help protect the species, but also inspiring and giving opportunity to a whole new generation of harrier-philes and conservation scientists.

Ryan is currently undertaking his PhD on Hen Harriers at the Galway-Mayo Institute of Technology.

Thank you to Ryan for supplying this, my first guest blog, please take time to comment or ask any questions to Ryan who is happy to respond on this blog.

The Irish Hen Harrier Winter Survey (IHHWS) was established in 2004 to explore what was until then a relative mystery; what do Hen Harriers do outside of the breeding season?

A new venture

When I came to Ireland in September 2009, one of my first hopes was to get involved in Hen Harrier monitoring and conservation on the island. I had completed my Master’s on Hen Harriers in Scotland and was keen to get involved!
One name synonymous with Hen Harriers is Barry O’Donoghue. I made contact with Barry and immediately realised that this was a person who, from a very young age had been dedicating his life to these birds and the conservation of their landscape. Barry was very supportive and facilitating and I soon began to check out a few suitable spots in my new home county of Sligo and contribute to the Irish Hen Harrier Winter Survey which he co-ordinated in his own time.
This brought me to some of the quietest and most remote parts of Ireland, watching over bogs and reedbeds at dusk in winter. For much of the time, it was a case of trying to find new roosts. Even in the worst of elements, those winter mornings and evenings provided a unique perspective and connection with nature. When a roost was found, it was hugely rewarding and big lift for the survey! Not alone would we have harriers to watch during winter evenings, but it would be a giant step towards protecting that site and yet another piece in the jigsaw, bringing us a bit closer to a fuller understanding of their non-breeding ecology.
I was one of hundreds of contributors to this study, which is still going strong after 17 seasons. During this time, numerous roosts have been made known to National Parks & Wildlife Service and a clear picture has emerged as to the species’ ecology and conservation requirements. Urgent attention is now needed in terms of translating this knowledge into policy to help a declining national population during this crucial period which accounts for two thirds of its annual lifecycle!

The Findings

Through a massive effort involving thousands of hours of coordinated surveys and thousands of records, great insight has been gained on Hen Harriers during the non-breeding period. More than 200 roosts have been discovered all across the island. Almost half of the roosts are in ‘upland’ locations, which is interesting because of the general assumption that Hen Harriers simply disperse to lowland/coastal areas in winter. More than half of the roosts are communal i.e. occupied by multiple birds on consecutive nights. The maximum number of Hen Harriers recorded at a communal roost on the one evening was 16!
Reliably counting multiple harriers at roost takes experience and skill, given the harriers will often drop to roost and rise again, meaning inexperienced surveyors might ‘double-count’ individual birds. Mostly, roosts hold about 1-3 Hen Harriers. It is important to consider that many of these roosts are not just important habitats for Hen Harriers, but for a range of species including Short-eared Owls, Merlin, Kestrel and Barn Owl.

Data provided from satellite tracked birds has identified new roost sites. A number of new roosts have also been located from tagged young birds dispersing from Britain, with two or three tagged Hen Harriers visiting and wintering in Ireland from Britain. These birds set up core wintering ranges around clusters of regularly used roost sites for several months between November to March. Some individuals have returned to winter in Ireland in consecutive years, finding their way to the exact same patch of bog as the previous year! The sat-tagged British birds often head back over the Irish Channel before the breeding season to their natal regions, or occasionally find new areas to attempt to breed. Similarly, Irish born birds have previously been recorded by Barry O’Donoghue to travel to Britain. Clearly, our Hen Harrier meta-population deserves more linked up conservation efforts between agencies and eNGOs in Ireland and Britain.

One of the most striking findings of the research has been that over the 17 years so far, almost a third (31%) of roost sites have been lost. Pressures and threats include the disturbance/removal of roosts (e.g. through burning and wind farm development) and changes to the surrounding landscape (e.g. agricultural intensification and afforestation with conifers). In a number of cases, roosts have been planted with forestry, even when these locations were made known to Forest Service. As things stand, there is effectively little by way of protecting hen harrier outside the breeding season.
A recent Bird Study publication arising from the IHHWS provides some positive and appropriate recommendations by supporting landowners to maintain roost habitats and improve habitat quality and prey availability in the areas surrounding roosts. This in turn could help farm income and boost wider biodiversity in the countryside.

“One of the most striking findings of the research has been that over the 17 years so far, almost a third (31%) of roost sites have been lost”

What now?

The IHHWS provides a solid platform on which to base necessary conservation action for hen harriers in Ireland. A holistic approach to conserving the hen harrier is now possible. One cannot protect a species by looking only at a quarter of its lifecycle or dependencies. It is known that the national Hen Harrier population is suffering from poor over-winter survival. Now that we know where Hen Harriers are, what they need and what threats and pressures they face throughout the year, measures can be put in place to address these.

Furthermore, it has been inspiring to watch a whole new generation of people getting to survey and know more about Hen Harriers, building their skillsets while simultaneously contributing to one of Ireland’s largest ecological studies.
I, myself am also grateful to the hard work of all these individuals, as I analyse in detail, the data that this long-running study has generated. Ultimately, it is hoped that all of this can help save the species here in Ireland.

Further information

A review of the Irish Hen Harrier Winter Survey published in Bird Study can be found here (this link is to be added soon)

The website of the Irish Hen Harrier Winter Survey is
Ryan Wilson-Parr is Honorary Secretary of the Irish Raptor Study Group and PhD candidate studying with Galway-Mayo Institute of Technology (GMIT). The research aims to investigate the wintering ecology of Hen Harrier and ascertain the seasonally and biogeographically disparate ecological requirements of Hen Harrier in Ireland and the implications for progressing an effective conservation strategy for the recovery of this declining species.

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