The bird was found on Monday by a member of the public and it was subsequently reported to the police.
A Police Scotland spokesman said: “Following an examination of the buzzard, the death does not appear to be due to natural causes and a wildlife crime investigation is being carried out.
“Anyone who lives nearby or may have frequented the area during outdoor pursuits activities and may have information regarding this crime or any offences against birds of prey is asked to contact police.”
The death is the first recorded this year, and comes as the number of birds of prey illegally poisoned in Scotland has fallen to its lowest level since records began in 1989.
RSPB Scotland revealed that a total of seven birds of prey, including a golden eagle and two buzzards, were killed as result of deliberate poisoning in 2012 - less than half the death toll of 17 birds in 2011.
The total number of poisonings is the lowest number ever recorded by the RSPB in Scotland. Only four years ago, in 2009, a total of 45 birds were illegal poisoned north of the border.
The wildlife conservation charity welcomed the decrease, but stressed that the illegal killing of raptors was still continuing at “wholly unacceptable levels” in some parts of Scotland
In addition to the seven confirmed incidents of illegal poisoning, there were a further 13 confirmed incidents of other forms of killing of birds of prey, including a golden eagle found shot in Dumfries and Galloway and another golden eagle killed by a trap in Angus.
Two of the illegal poisoning cases were in the Borders, two in East Ayrshire and one each in Highland, Moray and Dumfries and Galloway.