Two recent arrivals at the Clyde home of the UK's nuclear deterrent, are to be closely monitored using satellite technology, not as a security measure but to protect Britain's most threatened bird of prey.

The young hen harrier chicks have been satellite tagged at the MoD base in Argyll as part of a national RSPB project to protect and conserve this red listed bird species, which is of highest conservation concern in Britain.

The pair came from a nest of four young in the Royal Navy's high security Coulport base, which is the storage and loading facility for the UK’s Trident nuclear warheads. All four chicks were ringed and two, a male and a female, were tagged.

Hen harriers nest on the ground on upland moors. Their diet can include red grouse, which brings them into conflict with intensive grouse rearing on shooting estates.

They had been persecuted to extinction as a breeding bird on mainland Britain by 1900, but managed to recover their population naturally. However, ongoing illegal killing and disturbance threatens to drive the birds to the brink once more.

In 2013, hen harriers failed to breed successfully in England for the first time in almost half a century and in Scotland, their numbers fell by 20% between 2004 and 2010.

In that year there were 662 breeding hen harrier pairs in the UK, 505 of which were in Scotland.

The satellite tagging at Coulport was conducted as part of the RSPB’s part EU-funded Hen Harrier LIFE+ Project, a five year programme of nest protection, monitoring, community engagement and investigations.

The data gathered from the tags will be monitored, to see where the birds go and identify where they are most at risk.

Blánaid Denman, the RSPB's project manager said "According to an independent government report, Scotland should be able to support up to 1,790 pairs of harriers, but they are still being blighted by illegal killing and disturbance. As a result, these iconic birds are now missing from huge swathes of our landscape, when they should be an integral part of Scotland’s natural beauty. That’s why this type of work is so important, and why it’s so positive to see a large landowner like the MoD leading by example and championing these birds."

This Sunday will mark the third annual Hen Harrier Day with events across Scotland and England.