In today’s blog Dr Connie Tremlett, Conservation Scientist, updates on the progress of seabird surveys coordinated by the RSPB in 2023 to help us understand the impacts of Highly Pathogenic Avian Influenza (HPAI).
We are now coming to the end of a very busy field season of counting seabirds to better understand the impacts of the avian flu outbreak which began in north and west Scotland at the end of the 2021 breeding season and has since devastated seabird colonies throughout the UK and globally. Survey work has been underway across the UK, carried out by a range of conservation organisations, statutory bodies, volunteers and others (see previous blog by Linda Wilson).
This summer I have been focussed on managing a fantastic team of RSPB fieldworkers, who were specially recruited to fill anticipated gaps in seabird survey coverage across Scotland and Northern Ireland. After intense months of busy preparation at the beginning of the year, the fieldwork seems to have flown by!
The team worked extremely hard to complete their ambitious survey schedules, helped along by a lot of luck with the weather and with generous help from local staff and volunteers. The team covered hundreds of sites, focussing on counting Great Skua, Arctic Skua, Gannet, Guillemot, Kittiwake, large gulls, and terns; here I report on progress on Great Skuas and some of our cliff nesters.
The team (led by Matthew Marsh, Senior Research Assistant, and Adam Martin, Research Assistant, both covering sites on Orkney) counting cliff-nesters at Marwick Head. © Mike Pearce
Counting Great Skuas
Great Skuas (also known as Bonxies) nest on coastal moorland and were one of the species most severely impacted by HPAI in 2021/22, particularly concerning given Scotland hosts around 60% of the global population. The team surveyed approximately 250km2 of rough, hilly, boggy terrain, walking transects spaced 200-300m apart and recording the behaviour of all skuas encountered to work out whether birds were holding territories. You can watch the team in action on Lewis in the video below.
One sure way to identify a territorial Great Skua is dive-bombing behaviour - when the birds swoop low and fly at the head of the person intruding onto their territory to warn them off, it is a good sign that there is a nest or a chick somewhere nearby.
Areas surveyed by the team in 2023 had far fewer birds than were present before the outbreak, and sadly incidents of dive-bombing were much reduced compared to previous years. So, despite the inevitable discomfort when large birds fly directly at one’s head, these encounters were highly appreciated, showing that at least some birds had survived the outbreak and were holding territories in 2023. Thankfully, the team didn't come across any evidence of Great Skuas succumbing to the virus this year, with no fresh carcasses or sick birds found.
Nicola Morley (Senior Research Assistant covering sites on the Western Isles and west coast of Scotland), counting Guillemots on Handa Island. © Beth Thompson
Counting cliff-nesters
The team also spent hours staring closely at cliffs packed with dense colonies of seabirds, counting the number of Guillemot individuals, Kittiwake nests (as Guillemots lay their egg directly onto the rocky ledge, it isn’t easy to distinguish nest sites, whereas Kittiwakes build a structure from materials such as grass and seaweed) and breeding sites of Gannets. This was not an easy task! Especially when colonies were not visible from land and counts had to be done from a boat – looking through binoculars counting thousands of birds is a particularly good way to induce seasickness!
The picture so far looks much more variable for the cliff-nesters, with some sites showing increases in the number of birds compared to the last count, and some sites showing decreases – this video documents the changes seen by RSPB wardens at the Troup Head gannetry.
Avian flu comes on top of a long list of other threats faced by our seabirds, such as climate-change related changes in food availability and severe storms, and disentangling population change that can be attributed to avian flu will be difficult. The picture is further muddied by variable amounts of time elapsed since the last count, which we will also need to account for in our analysis.
Next steps
Once our own data are fully collated, our next step is to collate population counts done by other organisations and volunteers in 2023, which will be submitted to the Seabird Monitoring Programme (SMP). Seabird numbers and breeding success in Britain and Ireland are monitored by this scheme which is organised by the BTO in partnership with JNCC and RSPB.
Rebecca Jackson (Research Assistant covering Shetland sites) surveying for Skuas, complete with Skua deterrent stick attached to backpack (deflects divebombing Skuas which aim for the top of the stick instead of the head). © Joanne Monaghan
We will compare the numbers seen this year with previous count data, to try to understand what the impact of the avian flu outbreak in 2021-22 has been. The virus has behaved very differently this breeding season, not reaching Scotland until the end of June, and with a different dominant genotype that has had a greater impact on gulls.
At the time of our cliff surveys the team did not witness the scale of HPAI related mortality that occurred last year, unfortunately since then an increasing number of cliff-nesters have experienced further mortalities. This comes on top of the large outbreaks in black-headed gulls and terns that started earlier in the season. Sadly the avian influenza outbreak is far from over for many species and sites and further outbreaks in 2023 will have taken their additional toll.
Acknowledgements
Huge thanks to everyone who has undertaken seabird counts for this project, including the RSPB Conservation Science Department’s HPAI seabird surveyors: Liz Mackley, Matthew Marsh, Joanne Monaghan, Nicola Morley, Andrew Stronach, Hazel Watson, Samuel Healing, Rebecca Jackson, Adam Martin, Beth Thompson, Sophie Bennett, Miguel Hernandez Gonzalez, Lucy Williamson and Derren Fox.
We are grateful for funds provided by the ScotWind developers of the East and North East Plan areas, The Crown Estate (through the Offshore Wind Evidence and Change Programme), Scottish Government (via the ScotMer programme), Natural England, Department of Agriculture, Environment and Rural Affairs, and Natural Resources Wales.
This project is also supported by the RSPB Avian Flu Appeal. We are grateful for the additional support provided by BTO, NatureScot, Natural Resources Wales, Natural England, JNCC, National Trust for Scotland, National Trust, Scottish Wildlife Trust, Sea Mammal Research Unit, SOTEAG, Sarah Wanless, Mike Harris, and The Seabird Group. Our thanks go to all the SMP contributors who continue to submit annual data, many of them doing so as volunteers.
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