THE number of northern gannets on the Bass Rock has dropped by more than a quarter in less than a decade.

Thousands of the birds have died since avian flu was discovered across Scotland two years ago.

Now, researchers have highlighted the impact on the number of birds, which has shown recent signs of recovery, since 2014.

The latest findings were a result of a partnership between the Scottish Seabird Centre, the University of Edinburgh’s School of Geosciences, and the UK Centre for Ecology & Hydrology.

The group collected imagery from a state-of-the-art drone, implemented automated counts and combined this data with traditional seabird counting methods to help them understand the impact that bird flu had had on the island’s gannet population.

Avian flu has been spreading through seabird colonies around Scotland since 2021, causing widespread mortalities.

The disease was confirmed on the Bass Rock – the largest northern gannet colony in the world – in June last year, at the height of the gannet breeding season.

Following the discovery, thousands of seabirds died on the island, resulting in an extremely disrupted breeding season.

A colony count undertaken in June this year indicates that the size of the gannet population has decreased from 75,000 sites to about 55,000 sites.

A ‘site’ in the colony is an area which is occupied by a single bird or pair.

Emily Burton, conservation officer at the Scottish Seabird Centre in North Berwick, said: “We were devastated to see the impacts of avian flu on the Bass Rock colony during the 2022 breeding season.

“While it has been reassuring to see signs that the colony is starting to recover, avian flu remains a significant concern.

“Many of our internationally important seabirds are already affected by a range of pressures, including the impacts of climate change, invasive species, exploitation of the marine environment and pollution.

“It is more important than ever for the Scottish Government to accelerate the production of a Scottish seabird conservation strategy and prioritise actions that will restore and protect marine habitats.

“Without urgent action, some of our most iconic seabirds could be extinct within 30 years.”

Despite this significant decline, the 2023 breeding season has shown some hopeful signs of recovery, with no evidence of widespread mortality this summer.

Advances in the technology now available to monitor breeding gannets and interpret survey results have brought with it opportunities to better understand the colony in the wake of the disease.

The research on the Bass Rock this year has included drone surveys and machine learning trials, led by the University of Edinburgh’s airborne research and innovation facility.

Professor Mike Harris and Professor Sarah Wanless, fellows at the UK Centre for Ecology & Hydrology, added: “Until the outbreak of avian flu in 2022, the Bass Rock colony had increased relentlessly for more than a hundred years, becoming the world’s largest gannet colony in 2014.

“Over this period, counting methods have improved dramatically but the development of new technologies couldn’t have come at a better time and will give us the best chance of documenting how the gannets respond to the unprecedented impacts of avian flu.”