The birds were last tracked over grouse moors in Inverness-shire and Aberdeenshire.
A wildlife charity is appealing for information after two young satellite-tagged white-tailed eagles disappeared in “highly suspicious” circumstances.
Transmissions from the tags of both birds stopped on 22 July, with one last recorded over a grouse moor in Inverness-shire, and the other over an Aberdeenshire grouse moor.
According to RSPB Scotland, the Inverness-shire moor is in an area with a history of bird of prey persecution, including numerous suspicious disappearances of tagged golden eagles over several years.
These incidents led the Scottish Government to commission a review into the fates of satellite-tagged golden eagles in Scotland, with the subsequent report finding that a third of these birds had most likely been illegally killed.
Illegal persecution led to white-tailed eagles becoming extinct in Scotland in 1918. The birds have returned to the eastern part of the country through a reintroduction project run by RSPB Scotland, Forestry Commission Scotland and Scottish Natural Heritage between 2007 and 2012.
The birds that disappeared in July were both from the first generation of chicks from breeding pairs in the tiny white-tailed eagle population of east Scotland.
Ian Thomson, RSPB Scotland’s head of investigations, said: “Yet again, rare, protected birds of prey have disappeared in highly suspicious circumstances, with their last known locations on grouse moors. And yet again, we can be almost certain that these birds have been killed, with those responsible destroying all the evidence.
“The disappearance of these two eagles is more than a loss of two birds; it means any future breeding success they might have had, helping to boost the numbers of these rare birds, has also been destroyed. Illegal persecution is seriously undermining the re-establishment of a white-tailed eagle population in this part of Scotland.”
Satellite tagging technology allows conservationists to monitor the eagles as they establish and develop a breeding population following the reintroduction. RSPB Scotland said that in both recent cases the tag suddenly stopped transmitting with no prior evidence of any technical problems.
The National Wildlife Crime Unit and Police Scotland have been notified of the birds’ disappearance. Follow-up investigations by the police, including searches of the final known locations of the birds, have yielded no further information.
Mr Thomson added: “In 1999, Donald Dewar, Scotland’s first First Minister, described raptor persecution as a ‘national disgrace’, but twenty years on, it continues unabated.
“It’s clear that current legal deterrents aren’t working and is long overdue that the stain of raptor persecution was removed from our nation’s reputation by the introduction of robust regulation of a driven grouse shooting industry that is blighting our country’s incredible wildlife and contributing to its biodiversity crisis.”
Anyone with information about either of the birds or any other wildlife crime is urged to contact Police Scotland on 101 or call the RSPB’s raptor crime hotline on 0300 999 0101.