We compiled a dataset that reported on the numbers of dead birds from October 2021 to September 2023, including information from birdwatchers, government agencies and NGOs like the RSPB.

A total of 103,497 dead individuals (90,062 full grown and 13,435 chicks) of 155 species, plus another 3,976 individuals where the species could not be ascertained, were contained within 11,453 reports of dead birds received during the two-year period. Scotland and England accounted for most of the deaths, with the Great Skua, terns (Common Tern and Sandwich Tern), Gannet, Black-headed and Barnacle Goose among the most affected species. Over 7,500 bird carcasses were tested for HPAI, with 80 species testing positive. Mortality data closely matched the species testing positive, and there was a positive correlation between the seabird carcasses recorded and population changes observed in 2023.

The study demonstrated that mortality data can estimate disease impact, aid in real-time outbreak assessments and support better coordination during future events. Standardising data collection and linking to disease surveillance systems is recommended for an improved understanding of wild bird health.

We also looked for signals among data collected by volunteer ringers and birdwatchers. Analyses of ring recovery data can relatively rapidly detect excessive mortality in wild bird populations, including that arising from outbreaks of high pathogenicity avian influenza (HPAI). This is one way that we can first detect a major mortality event.

HPAI had such wide-ranging impacts that the effects were found in seawatching data on the eastern side of the UK from the Firth of Forth to Dungeness. We found evidence for changes in migration counts of four species with known HPAI mortality: Great Skua, Sandwich Tern, Black-headed Gull and Roseate Tern.

In terms of HPAI impacts, raptors have perhaps been the forgotten group as they tend to occur at low densities and in remote areas. Three papers from Scotland highlight the importance of long-term studies in helping to understand the impacts of HPAI. In Scotland, notable declines in breeding productivity among White-tailed Eagles and Golden Eagles were observed in2022, consistent with HPAI-related impacts. Common Buzzards in the Easter Ross Peninsula experienced a sudden reduction in occupied territories and fledging success during 2022 and 2023, coinciding with confirmed HPAI cases in nearby Pink-footed Geese. Peregrine Falcons in southern Scotland showed reduced productivity and increased breeding turnover post-outbreak, though population-level conclusions remained tentative. 

We carried out vulnerability assessments to identify the species and populations which are at greatest risk from the outbreak and used expert opinion to assess the likely effectiveness of conservation interventions in response to outbreaks of HPAI. 

No conservation interventions were identified as likely to result in a large reduction of the risk of high mortality in wild birds from avian influenza. The two most likely candidates, carcass removal and vaccination, both have significant practical challenges but may work in some circumstances and therefore warrant further testing. Restrictions on research activities, including ringing and tagging, may be counter-productive by reducing the evidence available to understand the impacts and inform wild bird conservation.

We have developed tools to inform future planning and decision-making.

Through a collaboration between EURING and EuroBirdPortal, funded by the European Food Safety Authority (EFSA), we have developed a migration mapping tool which can be used to predict the spread of avian influenza based on wild bird abundance and movements across Europe.

This process has identified a number of potential improvements in the way that data is collected, which will support more robust data collection in the future. Key recommendations are:

1. Enhance national and international wild bird population monitoring schemes, together with national disease surveillance schemes.  
2. Expand standardised carcass reporting and national testing of living and dead wild birds and integrate other data streams, such as ring recoveries, testing and population monitoring data for early detection.  
3. Invest in and continue to support long-term population studies, ideally multiple studies from across the range of species, to understand the mechanisms through which HPAI impacts wild birds.  
4. Develop spatial and temporal risk modelling for wildlife disease (e.g. BirdFlu Radar).  
5. Develop national rapid-response plans to deal with outbreaks, and establish networks of relevant stakeholders and communication pathways.  
6. Ensure that networks follow a One Health approach and include the relevant environmental, animal and health agencies and eNGOs, among the stakeholder groups.  
7. Ensure that pre-approved data collection methods and protocols are in place for future outbreaks.  
8. Prioritise high-risk species: apply vulnerability assessments to guide conservation action.  
9. Invest in research to better understand areas of uncertainty around impacts on wild birds, and the transmission interfaces between birds, their environment, livestock and humans within a OneHealth framework.  
10. Understand the different mechanisms behind population recovery (or otherwise) of wild birds after mass-mortality events.  
11. Take a global perspective, standardise data collection and coordinate across flyways and governments to align efforts. 

Now the emergency response is over BTO is looking to undertake some of the recommendations. In the Defra-funded project iPREPARE, together with APHA, we are expanding the live testing of seabirds for avian flu viruses and antibodies with the Universities of St Andrews, Liverpool and Essex.  Also, as part of this project, to better understand the interface between wild birds, poultry, other livestock and humans, we have started a GPS tracking project of Carrion Crows in landscapes with and without livestock. 

We continue to develop our predictive capabilities to predict future HPAI presence using the BirdFlu Radar and, together with Natural England are looking to develop more robust detection and monitoring of seabird wrecks.