Inquiries are continuing into the fatal poisoning of an eagle, known as Fearnan, found after satellite tracking equipment showed she was static in the same place on Glen Lethnot, Angus, for several days last month.
Wildlife artist Keith Brockie, a member of Tayside Raptor Study Group who has been monitoring birds of prey since the mid-1970s, was part of the team that attached trackers to Fearnan near Loch Tay in June 2011. The bird spent much of its life in Badenoch before moving to the Angus glens only last month.
Mr Brockie said the grim discovery is another addition to a growing death toll of birds of prey on red grouse shooting estates.
He said: "Four golden eagles with satellite tags have died on Angus estates in the last five years. Given that less than 10 per cent of eagle chicks are tagged, you can easily speculate what has happened to another 36 golden eagles in Angus.
"Virtually all of the eagles that are found dead have been killed illegally. All of the estates are trying to maximize the number of red grouse that are on the moors, so they try to kill anything that impacts on that."
A Scottish Gamekeepers Association spokesman said "significant progress" had been made in recent years and described the incident as "terrible".