Two hen harriers have disappeared in suspicious circumstances, prompting an appeal by police and conservationists.
The birds, named Saorsa and Finn, were fitted with satellite tags allowing experts to follow them.
Saorsa was tagged at a nest in Ross-shire in June 2017 which suddenly stopped transmissions in the Angus glens on February 16.
Data from the device showed she had been in the area since November 2017 but experts say she has not been seen or heard from since.
A spokesman for Balnagown estate, near Tain in Sutherland, said: “Saorsa hatched and fledged from Balnagown estate, and it was an honour and privilege to be able to follow her progress.
“Saorsa’s loss is deeply felt by all concerned as we strive hard to assist with conservation and protection of our wonderful wildlife.”
Finn was tagged on a nest in Northumberland in July 2016 and showed movements into southern Scotland until March 25 when transmissions stopped in Moffat, Dumfries and Galloway.
Duncan Orr-Ewing, RSPB Scotland’s head of species and land management, said: “The sudden disappearance of these protected rare birds shows that current legislation is not sufficient.
“We believe the introduction and enforcement of licensing of ‘driven’ grouse shooting is now vital to help protect the hen harrier, as well as asserting other public interests in the way large areas of our upland landscapes are managed both sustainably and within the law.”
A spokesman for the Scottish Gamekeepers Association said: “As an organisation, there are very few full-time gamekeepers in the Moffat area for us to make inquiries.
“The loss of tag transmission in Angus, like the tag in Moffat, merits further, independent, investigation.
“There has been a commitment in Angus over the last few years to changing past reputations.
“The high numbers of raptors on local moors are proof of that and the first harrier breeding attempt for some time, last year, in the region was a sign of progress.”
Anyone with information on the incidents has been asked to contact Police Scotland on 101.