Scientists have made the remarkable discovery that northern gannets can recover from avian flu and that the iris of those gannets which survive the infection turns from a normal vivid blue to black, an indicator of a previous infection.
A detailed study on the impact of avian flu was carried out on the Bass Rock in Scotland which is home to 150,000 gannets, the largest single gannet colony in the world that was impacted by an outbreak of avian flu last year.
Whilst the virus responsible for avian flu has been affecting both domestic and wild birds for decades, the current outbreak appears to have been severely impacting seabirds, especially gannets.
Researchers examined the numbers and breeding success of the Bass Rock gannets and whether they were potentially able to recover from an infection.
Black irises – instead of the vivid blue – were first seen in gannets breeding on the Bass Rock last June with colour varying from completely black to mottled.
The team took blood samples from 18 apparently healthy adult gannets with both normal and black irises which were tested for bird flu antibodies to determine whether the birds had been previously infected. Eight tested positive, of which seven had black irises.
Jude Lane, RSPB conservation scientist and lead author of the study says, “This has been a fascinating development and the discovery may prove a useful non-invasive diagnostic tool. The next steps are to understand its efficacy, if it applies to any other species and whether there are any detrimental impacts to the birds’ vision.”
Lane added that ophthalmology tests will be needed to determine what is causing the black colouration.
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A survey of the Bass Rock will take place later spring using a drone to make a detailed assessment of the current population of gannets.
The CEO of the Scottish Seabird Centre Susan Davies says, “For now, we have no obvious signs of avian flu in the colony and birds with signs of infection – the black eye – have returned which suggests some level of immunity may be present and gives us hope for the future.”
Main image: Northern gannet showing black iris, indicating exposure to avian flu © Emily Burton/Scottish Seabird Centre
