The sound of a seabird colony is overwhelming. The air is thick with kittiwakes, ??guillemots, razorbills and shags. Shrieks and calls ricochet down the cliffs and the rhythmic flap-flap of wings cuts the air like -stadium applause. Birds ride the wind in spirals, dive to the waves, burrow into shelves in the cliff face or settle on rocky promontories.

The summer breeding season is coming to an end for many of the species at St Abb’s Head nature reserve in Scotland’s East Lothian, 50 miles east of Edinburgh. Adult guillemots and their chicks have already migrated to their wintering grounds. I’m sitting on a grassy verge at the cliff’s edge, overlooking the rocky bay that houses the colony, with Ciaran Hatsell, a National Trust of Scotland ranger. “I get empty nest syndrome at the end of the season,” Hatsell says, half smiling. “It’s like 60,000 of your kids leaving all at once.”

Hatsell knows about loss. On June 5, he discovered the first signs of avian influenza in one of the gannets. Since then it has wiped out thousands of birds on the reserve. The flu is a highly pathogenic strain of the H5N1 virus. Since its early detections in poultry and wild birds in the spring of 2021, this new strain has killed more than 86 million birds in the US and Europe alone, predominantly through poultry culling, the mass slaughter of birds at sites where cases have been found. The European Food Safety Authority said the 2021-2022 -epidemic season was the largest ever recorded on the continent.