Gannet populations at two of the world’s largest colonies are not expected to recover from the impact of 2022’s bird flu outbreak for almost two decades.

A new study from the RSPB said seabirds on Bass Rock, off Scotland’s east coast, and Grassholm, off the Pembrokeshire coast in Wales, had suffered an “unprecedented deadly blow” during the outbreak.

It led to a fourfold increase in adult gannet deaths, resulting in a 26% decrease in the size of Bass Rock’s colony and a 38% fall at Grassholm.

While the outbreak was already known to have killed tens of thousands of birds, the study warned that the colonies would not fully recover from the impact until 2041 at the earliest.