Population-level impact and geographic spread of highly pathogenic avian influenza virus H5N1 outbreak in gannets

For some unfortunate observers, the summer of 2022 will be remembered for an outbreak of highly pathogenic avian influenza (HPAI), which led to the death and suffering of many thousands of seabirds at colonies across the North Atlantic. These internationally important populations were already under intense pressure from anthropogenic change; therefore, we need to know urgently not only the impact of this outbreak but how it might be spreading. We propose using detailed individual-based data to estimate the impact of HPAI on a species particularly severely impacted in the recent outbreak, the northern gannet. Using capture-mark-recapture techniques we will estimate adult survival probability, a much more robust measure than conventional population censuses or counts of dead birds, at two large UK colonies - one which has been severely impacted by HPAI (Bass rock in Scotland), while the other remains virus free (Grassholm in Wales). We will also track inter-colony movements using bird-borne GPS devices which transmit via the mobile phone network. This will provide vital information on which components of the population are most likely to spread the virus (by comparing the usually colony-faithful breeders with the more itinerant immature birds) and inform our metapopulation model for gannets in the northeast Atlantic. This model will enable us to predict the impact of HPAI across virtually the entire gannet breeding range, under the realistic scenario of inter-connected colonies. Finally, we will be able to identify populations particularly vulnerable to the combined effects of viral outbreaks and other anthropogenic stressors such as the construction of offshore wind farms.