Majestic and rare, white-tailed eagles boast an immense wingspan and are one of Scotland’s great wildlife reintroduction success stories.

But fears are now growing for Scotland’s most impressive raptors after one of a breeding pair found dead on the Isle of Skye tested positive for deadly avian influenza.

It’s thought the adult bird may have fed on the infected corpse of a goose that had migrated to west coast of Scotland for winter.

The discovery marks the first time that avian influenza has been confirmed in the species, which was reintroduced in the mid-1970s after having been hunted to extinction by Victorian pleasure seekers.

There is now deep concern that the extremely infectious virus is spreading at an alarming rate among migrating geese, posing a potentially deadly risk both to their numbers and the highly protected white-tailed eagle population which is known to scavage on carrion.

Bird flu has already swept through colonies of barnacle geese on the Solway Firth where the bulk of the birds which have travelled south from Svarlbard in Norway, spend their winters.

It’s estimated that 3,000 birds among the 35,000 strong Solway populations have already died, with distressing reports of sick and dying birds in distress on both north and south banks, and others seen plunging from the sky in mid-flight.

Most are barnacle geese but there have also been reports of dead whooper swans and pink-footed geese, both of which migrate from Iceland to spend milder winters in the area, and a kestrel.

The intensity of the virus has shocked birdwatchers: within a week of one dead swan being identified with bird flu in the Solway area in November, birds were said to be dying at the rate of dozens every day.

The sight of scores of carcasses and sick birds has alarmed visitors to the RSPB Mersehead Nature Reserve near Dalbeattie and Caerlaverock National Nature Reserve in Dumfries and Galloway. A major biosecure clear-up operation is being carried out to remove the infected carcases.

Avian influenza has emerged in both wild and farmed birds across the UK over the past year, however cases are spiking as migratory species arrive for winter.

The UK’s chief veterinary officer Dr Christine Middlemiss has described the outbreak as at a “phenomenal level” and confirmed that lessons from the foot and mouth outbreak are being used to try to contain the outbreak.

The UK Government’s Animal and Plant Health Authority (APHA) has imposed disease control zones in affected areas stretching from Essex to Gretna, where last week a flock of free-range hens at a poultry facility around 20 miles from the Caerlaverock and Mersehead reserves - was ordered to be culled after testing positive for avian flu.

Tight restrictions have been imposed on the premises at Raeburnhead, Kirkpatrick-Fleming, and in the area around it, but it is impossible to control the movement of wild birds.

Paul Walton of RSPB warned: “We are in unchartered territory.

“It’s not unusual for there to be a few cases of bird flu each year. But the avian influenza outbreak we have at the moment is easily the biggest I can recall by a long way.

“It’s a real worry, this is a big outbreak and we don’t know how this is going to play out.”

The dead white-tailed sea eagle was found by a walker in north Skye last month. Its body was retrieved by the local RSPB and post-mortem tests confirmed avian influenza.

White-tailed eagles were declared extinct in the UK in the 1920s after years of persecution, however a reintroduction programme saw birds from Norway released on the isle of Rum in the mid-1980s.

There are around 150 pairs, mostly located on the western seaboard.

The birds’ successful reintroduction recently led to it being the only bird to be removed from this year’s Birds of Conservation Concern’s ‘red’ list of most threatened species.

However, because white-tailed eagles do not begin to breed until they are five or six years old, increasing the population is a slow process meaning the loss of any bird is blow.

Skye-based bird enthusiast, Bob McMillan, said: “This loss is significant.

“We have a population of 20 plus breeding pairs of white-tailed eagles, with a lot of sub-adult birds, and they will feed on carrion in wintertime and take live geese.

“Greylag geese breed extensively on some of the islands and there’s a wide population of barnacle geese. So if there are greylag or barnacle geese which are easy for them to take because they’re weak and ill, they will pick them off.”

“There’s been a huge investment in the ongoing monitoring of white-tailed eagles, and it does feel like this poses a significant risk.”

Concerns for the white-tailed eagles comes after the virus seriously affected populations of great skua, also known as bonxies, in the northern isles in late August.

At least 65 dead birds were discovered on Fair Isle, and more than 30 located on St. Kilda and other areas of Shetland and the Orkneys. There were also reports that the outbreak appeared to have decimated the breeding season, with far fewer chicks than would normally have been expected.

Mr Walton said the origins of the outbreak remains a mystery, while its spread and the risks it poses is “beginning to cause real concern”.

He added that people encountering sick or dead birds – particularly wild fowl, geese and birds of prey – should not touch them and suggested cleaning garden wild bird feeders and bird tables regularly with mild disinfectant.

“We ask everyone to stay vigilant. We can’t say how this will go, it’s pretty unusual situation and really hard to see what will happen,” he added. “One would hope it’s going to slowly start to ease off but we just don’t know.”

A Scottish Government spokesperson said: “Following a number of cases of avian influenza in both wild and kept birds in the UK, the Chief Veterinary Officers across the UK agreed to bring in new housing measures, which came into force on 29 November.

“These measures build on the strengthened biosecurity requirements that were brought in as part of the Avian Influenza Prevention Zone (AIPZ) on 3 November 2021. The AIPZ means all bird keepers (whether they have pet birds, commercial flocks or just a few birds in a backyard flock) are required by law to undertake a range of biosecurity precautions.

“Public health advice is that the risk to human health from the virus is very low. Food standards bodies advise that avian influenzas pose a very low food safety risk for UK consumers, and it does not affect the consumption of poultry products including eggs.

“As part of routine wildlife disease surveillance, post-mortem examinations of birds are undertaken where any ‘at risk’ species, in particular, any wild ducks, wild geese, swans, gulls, are found dead.

“We ask that the public remain vigilant and report any findings of dead wild birds and that they do not touch them or pick them up.”