New study shows long-lasting effects of bird flu on Gannet colonies - RSPB

Two of the world’s largest colonies may not recover from the impacts until 2041 at the earliest.

According to a new study led by the RSPB and Aarhus University, Gannet populations at two of the world’s largest colonies, Bass Rock in Scotland and Grassholm in Wales, are not expected to recover from the impact of bird flu until 2041 at the earliest.

The findings show bird flu was responsible for a fourfold increase in the deaths of adult Gannets. The UK is responsible for a high proportion of the global population.

A decimated population

In the 11 years prior to 2022, the average annual mortality rates were 6% at Bass Rock and 11% at Grassholm. During the outbreak, this rose to 33% and 47% respectively.

In 2023, a year after the outbreak, this led to a 26% decrease in the size of the colony at Bass Rock and a 38% decline at Grassholm.

A very slow recovery

Adult breeding birds drive the growth of population in seabird colonies. Therefore, the spike in deaths will have a profound negative impact on the overall population size, and future sustainability.

Population modelling forecasts that the colonies are unlikely to recover to the size they would have had until 2041, 19 years after the outbreak.  In reality, recovery could take even longer.