Anonymous donors have raised the stakes in the hunt for the killers of two golden eagles in separate incidents this year.

Both were found poisoned within the Cairngorms National Park. Police inquiries have failed to nail the culprits and the Royal Society for the Protection of Birds in Scotland (RSPB Scotland) put up a reward of £1,000 for information leading to the arrest and conviction of the killers in each event.

Now, two anonymous donors have upped the stakes and raised the cash on offer to a total of £10,000.

One of the donors offered to cover the RSPB Scotland’s original offer and a businessman has put up an additional £8,000, which means a reward of £5,000 is being offered for information on each killing.

The first bird was found on the Dinnet and Kinnord Estate near Ballater on 13 May and the second at the Glenfeshie Estate in the Cairngorms on 10 June. Analysis of the bodies of both eagles revealed they had been killed by the banned pesticide carbofuran.

Under the Wildlife and Countryside Act 1981 it is an offence for any person to intentionally or recklessly kill or injure a wild bird.  It is also an offence to possess carbofuran poison.

Duncan Orr Ewing, of RSPB Scotland said: “The fact that two people, both of whom were previously unknown to the RSPB and are not members, have been motivated to approach us and offer £10,000 to help the appeal to catch these criminals is indicative of the public outrage at these crimes.

“We are grateful for their support and hope it leads to convictions in these deplorable cases.”

The donor of the £8,000 told RSPB Scotland: “‘I simply cannot believe that anyone would wish to kill such a magnificent and awe-inspiring creature as a golden eagle.

“It is a sad and shameful state of affairs that some people judge it acceptable to carry out this practice in our society today. It is my hope that this donation will serve as a reminder how abhorrent the vast majority of right thinking people view this activity, and help to stamp it out altogether.”

RSPB Scotland says outraged bird lovers have flooded RSPB Scotland with messages of support since the charity offered rewards for information leading to the prosecution of those responsible for poisoning two protected golden eagles.

Police say anyone who finds a dead bird or a carcass they suspect may have been left there as poisonous baits should not to touch anything and report their finding to the police immediately.

Officers further advise the public to avoid touching the area as potential evidence may be destroyed. Branches or grass and turf should be thrown over the bait to prevent it being seen and consumed by animals and birds.