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Rarities & Conservation: Bird Flu’s Devastating Toll on the UK’s Wild Birds​

27 June 2025
By James Hamilton
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Greylag Goose with HPAI by Hugh Insley / BTO

​Over the past three years, avian influenza has emerged as a rapidly escalating threat to wild bird populations around the world. Here in the UK, we have witnessed significant levels of mortality in our internationally important breeding seabirds and wintering waterfowl, as well as impacts on vulnerable bird of prey populations.

The British Trust for Ornithology (BTO), working with its publishing partner Taylor & Francis, has brought together a suite of scientific studies across two issues of its journal Bird Study. These studies both document the spread and impact of the disease on wild birds and assess the effectiveness of management responses. By doing this, BTO hopes that lessons learned from the recent outbreak will help ensure we are better prepared for future outbreaks of this, and other, diseases.

Collectively, the studies reveal the unprecedented scale and spread of avian influenza. It decimated seabird colonies in the UK and Europe before moving along multiple pathways through Africa, North and South America, and eventually reaching South Georgia and the South Sandwich Islands in the South Atlantic in September 2023.

Originating on a goose farm in China in 1996, the HPAI virus has caused global economic damage to poultry flocks and high levels of mortality in wild birds, especially migratory wildfowl. It is now endemic in wild birds, making them both the unintentional victims of a disease that evolved from the farming industry and global carriers of the virus.

Among the hardest hit species:
  • Great Skuas experienced an estimated 73% collapse in their UK breeding population, representing a loss of around 45% of the global population.
  • A third of Svalbard’s Barnacle Goose population, which winters on the UK’s Solway Estuary, was lost to the disease.
  • Approximately one-fifth of Northern Gannets were estimated to have died at some breeding colonies.
  • Breeding Terns and Gulls were severely affected across Europe, including at key UK colonies.
  • Notable declines in the breeding success of Scotland’s White-tailed Eagles and Golden Eagles were likely linked to contact with infected prey or carrion in coastal areas.
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Importantly, the editors overseeing these scientific papers have identified several recommendations to help conservation bodies, land managers, and others better monitor future mortality, respond to major outbreaks, and understand the scope, scale, and implications of this disease for wild bird populations.

“This was a conservation crisis unfolding in real time,” says Lead Editor Professor Phil Atkinson. “Being able to quickly bring together data and expertise from across BTO and its partner organisations enabled us to respond to a rapidly evolving situation, and then reflect on the lessons learned. Our collective findings call for urgent investment in long-term monitoring, improved approaches to disease response, and greater integration of wildlife disease surveillance into public health and environmental policy. This should be done under a ‘One Health’ framework, which considers human, livestock, and wildlife health together.”
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Professor James Pearce-Higgins, BTO Director of Science and contributor to the issue, added: “The last three years have shown the power of citizen science - birdwatchers, surveyors, and bird ringers - combined with BTO analysis, to track the spread of the disease and its impact on bird populations. It is essential that these long-term surveillance schemes are maintained and enhanced to monitor ongoing disease impacts and to support the recovery of vulnerable populations. We encourage birdwatchers to take part in our monitoring schemes and to report any sick or dead birds they find through our BirdTrack app.”

BTO warns that future bird flu outbreaks, along with other environmental pressures, could push vulnerable species beyond recovery. Without action, the disease also continues to pose a significant risk to poultry and an increasing risk to humans and livestock.
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The 20 studies, along with two editorial overviews, are available as a virtual collection online and can be accessed by researchers and practitioners. All papers in the collection are free to view for at least the next three months.
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