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

Old blue eyes? A gannet with its usual blue iris coloration (above) and one in which the iris has turned black. Photograph: Jude Lane

The vivid blue irises of northern gannets turn black if they survive avian flu, according to a 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.