An Argyll farm manager has pled guilty to possessing the banned pesticide carbofuran.
Tom McKellar, 50, kept the highly toxic poison at the Auch Estate, near Bridge of Orchy.
Police were first alerted when an adult golden eagle was found dead in the area after being poisoned with carbofuran.
Sentence on McKellar, who admitted setting out meat laced with the poison as bait for foxes, was deferred at Oban Sheriff Court.
A single grain of carbofuran can kill a bird, while a quarter teaspoon can be fatal to humans.
Following a search of his property by police on 17 June 2009, McKellar was found to have quantities of carbofuran in three separate containers and traces of it within a syringe.
A group of hillwalkers had telephoned RSPB Scotland 11 days earlier to report finding the body of a golden eagle on the slopes of Beinn Udlaidh, near Bridge of Orchy.
RSPB Scotland investigations staff, accompanied by a wildlife crime officer from Strathclyde Police, retrieved the body as evidence.
Tests by Scottish government laboratories revealed that the adult golden eagle had been poisoned with carbofuran, which has been illegal to possess or use in the UK since 2001.
A follow-up search of land and buildings on the Auch Estate revealed a dead fox, which had been poisoned, and a sheep carcass laced with carbofuran.
Sheriff Douglas Small deferred sentence on McKellar until social inquiry reports had been prepared.
Defence agents will outline the mitigation for the offence when the case resumes on 29 May.
Welcoming McKellar's conviction, Scottish SPCA Chief Superintendent Mike Flynn said: "The persecution of wildlife is of great concern to the Scottish SPCA and the possession of carbofuran is a serious offence that will not be tolerated.
"We are very pleased with this conviction, which demonstrates that when organisations work together perpetrators will be brought to justice."
Scottish Land & Estates, which represents 2,500 landowners across Scotland, said the conviction of McKellar underlined the need for "cool heads and hard facts" in the debate over wildlife crime.
Its chief executive, Douglas McAdam, said: "Our members are committed to the eradication of wildlife crime and the possession and use of illegal pesticides is to be condemned out of hand.
"This was a very high profile case and when it first emerged a golden eagle had been found poisoned there was a knee jerk response from some quarters trying to imply that landowners or country sports would most likely be involved in some way.
"This, of course, is not the case here and it demonstrates the need for cool heads and hard facts when these dreadful incidents occur".
At an earlier hearing in December 2010 at the High Court in Glasgow, McKellar pled guilty to various firearms offences and was sentenced to 300 hours community service.