The poisoning of two golden eagles has seen RSPB Scotland offer a reward for the first time in its history to help catch the culprits.
RSPB Scotland said it was determined to catch the culprits
The deaths in the Glenfeshie Estate in the Cairngorms and Dinnet and Kinnord Estate near Ballater, in Aberdeenshire, are being investigated.
RSPB Scotland is now offering £1,000 for information on each death which leads to arrest and conviction.
It said the deaths, which took place in May and June, were "dreadful crimes".
The Ballater death being probed by Grampian Police happened on 13 May, and Northern Constabulary is investigating a similar incident in the Cairngorms from 10 June.
It is the first time RSPB Scotland has offered a financial reward for information in relation to the death of a bird.
It hopes the move will highlight the serious nature of this type of crime, as well as underlining the RSPB Scotland and police determination to detect those responsible and bring them to justice.
It is understood that both birds were poisoned using illegal carbofuran poison. Possession of this substance is in itself a crime.
Stuart Housden, director of RSPB Scotland, said: "Golden eagles are magnificent icons of the Scottish uplands.
"We should be proud that Scotland supports some 442 pairs of these awe-inspiring birds that attract tourists from all over the world.
"Yet some in our country selfishly persecute these birds, through the use of poisoned baits or other means. In the space of just three months, two dead eagles have been found - killed illegally."
Police hope the RSPB Scotland reward will help the appeal
Grampian Police wildlife officer Dave MacKinnon: "We look forward to developing our partnership with the RSPB Scotland in relation to what is a very serious offence.
"Hopefully, the reward will stimulate the public to come forward with information and we can trace those responsible."
And Northern Constabulary wildlife crime co-ordinator John Bryden said: "The force takes any type of crime against wildlife very seriously and we are continuing our inquiries into this incident.
"Obviously we are delighted that the RSPB Scotland has opted to put up a reward in relation to this crime and we hope that someone with information will come forward."
Anyone with information can contact either Northern or Grampian, or Crimestoppers, or the Campaign Against Illegal Poisoning of Wildlife on 0800 321 600.