Officers from the Royal Society for the Protection of Birds in Scotland also suspect a third bird - an adult male - has been killed, although no remains have been found.

The dead eagles were found at a site in Kingussie, Strathspey, by a member of the Raptor Study Group, a network of volunteers which monitors birds of prey.

Poisoned bait

The incident was reported to the RSPB and a police inquiry was launched.

A post-mortem examination found the birds had been poisoned with the highly toxic insecticide Carbofuran.

The dead eagles were found at Kingussie

It is believed the male eagle picked up poisoned bait and carried it back to the nest where it was eaten by the other birds.

Carbofuran has been used in other poisonings and the eagles may have been the victims of the misuse of poisons directed at other birds of prey or wild animals, said an RSPB spokesman.

However, officers were not ruling out the possibility that the bait was deliberately laid for the eagles.

The RSPB said it had been 10 years since two golden eagles from the same nest were found poisoned, the only similar reported incident.

Senior investigation officer for the RSPB in Scotland, Dave Dick, said: "There are 430 pairs of golden eagles all over Scotland. Fortunately this is a rare event."

Charges unlikely

Officers at Northern Constabulary investigating the case say it is now unlikely anyone will be charged over the incident.

As the site where the birds were killed is remote there would have been few, if any, witnesses and the nature of the crime means offenders would be difficult to trace.