Avian Influenza in UK Raptors

EXPERTS fear bird flu in seabirds could cause problems for coast-dwelling Scottish birds of prey.

A report from the Royal Society for the Protection of Birds last week revealed that avian influenza had taken a huge toll on Scotland’s seabird populations.

Scotland’s population of great skuas – colloquially known as “bonxies” – have declined by 76% since 2021.

Gannets and roseate terns have also been seriously impacted by bird flu.

Hannah Sloan, a falconer, says problems may arise as raptors usually take the opportunity to scavenge on the dead to conserve energy.

“Bird flu transfers really quickly and can transfer even if the infected animal is dead,” she said.

“So, if a bird of prey eats the seabird that has avian influenza, it then gets influenza and dies.

“It can also happen if a mammal predator eats a seabird and then dies of avian influenza and is then scavenged on by a bird of prey so it’s basically through the food chain usually.”

She says less is known about the impact of avian influenza on birds of prey as their reclusive nature makes it difficult to study how the disease affects them.

“They’re solitary,” she explained. “If they get bird flu and they die in the wild, they would most likely never be found as they would be in woodland areas or outwith where people really frequent and if they were to die it’s most likely that there’s another scavenger around that would eat it anyway.”

Sloan says it is important that further research that is tailored to the bird’s behaviour is conducted in the future.

“Seabirds are colony birds, meaning they die en masse, so that’s a bit hard to not notice when you’ve got hundreds of birds lying on a beach dead – they’re obviously going to be tested, but if a bird no-one knows dies, it isn’t going to be tested,” she said.

“It’s definitely something that needs to be looked into before there is another outbreak of avian influenza and it does affect conservation of birds of prey.”

NatureScot published a report in June revealing that the breeding success of birds of prey – particularly eagles – may be impacted by avian flu.

White-tailed eagles seemed to have been the most impacted in coastal areas, which suggests a potential link between infected seabirds and the eagles that may have scavenged upon them.

The organisation now says it is working on repeat analysis of its previous report to see whether there are any continuing issues.

Duncan Orr-Ewing, head of species and land management at RSPB Scotland said: “In the past couple of years – certainly last year – there were quite a lot of records of young sea eagles – birds at the point of fledging – dying in the nest and these birds were tested and confirmed to be positive for avian influenza.

“So, it doesn’t appear to affect the adult sea eagles but it’s affecting the young birds in the nest and of course, for the young birds in the nest, one of the main prey items of sea eagles is seabirds, meaning there may be a transmission issue there.”

He says that birds of prey tend to die within a day or so of contracting avian influenza due to how debilitating it is for them – especially chicks.

Orr-Ewing added: “We have 170 breeding pairs of sea eagles in Scotland and last year – less so inland but more on the West Coast areas where the birds are feeding on seabirds – there was big mortality in chicks, so, effectively, there was very little productivity in that year.

“So, we’ve lost a year’s productivity to a large extent, and large parts of the sea eagle West Coast range, which is where most of the pairs are, so that will delay the expansion of the population of sea eagles – which is one of our rarest breeding raptor species.”