John Dodd, co-founder of Edinburgh-based firm Artemis, is reported to have sold the 10,000-acre Glenogil shooting moor in the Angus Braes to a German, Baron Ferdinand von Baumbach.
Glenogil is widely regarded as one of the country's leading grouse, partridge and pheasant shooting estates and has been at the centre of a number of alleged incidents of wildlife crimes.
A dead white-tailed sea eagle was found by RSPB staff on the estate boundary in 2009. The bird had been killed by the illegal pesticide carbofurin.
Mr Dodd, who has never been prosecuted for a wildlife offence, said in the past his staff felt they were "being constantly targeted". Sources close to the landowner say he sold for "personal reasons" and not because of the controversy.
Jennifer Dunn, a spokeswoman for the League Against Cruel Sports, said: "There have been a lot of problems around Glenogil and we hope the new owner will work very hard to protect wildlife in the area."
In 2008, Mr Dodd had his farming subsidy cut by £107,000 by the Scottish Government after poisoned baits were found on his estate. It was the largest civil penalty imposed under EU "cross-compliance" legislation, which makes protection of wildlife a condition of subsidy.
Mr Dodd denied any wrongdoing by him or his staff and said he was horrified by allegations of bird persecution. He bought Glenogil for £4.5 million in 2003 and is reported to have invested heavily in the area and renovated many buildings on the estate.
In 2007, Mr Dodd said the purchase was "a once-in-a- lifetime opportunity to be the caretaker of a very special bit of Scotland" and a wonderful place to bring up a family.
Glenogil's sale comes 15 months after ministers introduced a vicarious liability clause in the Wildlife and Natural Environment (Scotland) Act 2011, which means landowners can now be held criminally responsible for the actions of their employees.
The clause is thought to have cut fatal bird-of-prey poisonings from 28 in 2010 to three in 2012.