Observations at north-west Scottish Gannet colonies in 2023 in the context of an outbreak of Highly Pathogenic Avian Influenza in 2022

Opportunistic photos taken in 2023 (mainly in August) at the six poorly monitored gannetries in the north and west of Scotland of Sule Skerry, Sule Stack, Sula Sgeir, the Flannan Isles, Ailsa Craig and Scar Rocks were used to help understand the status of these colonies following the 2022 outbreak of Highly Pathogenic Avian Influenza. Our observations suggest that all except Scar Rocks may have undergone population declines since they were last surveyed 5–9 years ago and that this is most likely due to the 2022 HPAI outbreak. Only a few dead birds were observed which was in line with the virus having a much-reduced impact in 2023. Productivity appeared to be reasonable, although some chicks appeared to be unattended. The median hatch date (derived from chick plumage characteristics) was earlier at the northernmost compared to southernmost colonies, which was opposite to what was expected based on previous work, though this may be unrelated to HPAI.