Irises of gannets that survive avian flu turn from black to blue, study finds

‘Fascinating’ discovery could prove a useful non-invasive diagnostic tool to apply to other species, say scientists

The vivid blue irises of northern gannets turn black if they survive avian flu, according to a new study which provides evidence that some wild birds are shaking off the deadly virus.

Avian flu has killed wild and domestic birds for decades but the current strain (H5N1) severely affected seabird populations across the North Atlantic last year, with particularly high death rates among gannets.