Here are the key events in the investigation:
March 25, 2014 – Police confirm they are investigating the deaths of five red kites and a buzzard
March 28, 2014 – The death tool rises to 13 and police say initial signs are that they were poisoned
March 31, 2014 – The RSPB put up a £5,000 reward for information.
April 1, 2014 – It is confirmed that 16 birds have been found dead.
April 3, 2014 – An anonymous donation doubles the reward to £10,000.
April 7, 2014 – A 17th raptor is discovered dead as RSPB officer Brian Etheridge calls for an amnesty for farmers and gamekeepers to hand over banned pesticides.
April 9, 2014 -Police teams raid a series farms on the Black Isle as the death toll rises to 19. Police reveal tests have shown at least 12 of the birds were poisoned while local landowners donate £12,000 to the reward.
April 13, 2014 – Hundreds of people march through Inverness in protest against the poisonings.
May 8, 2014 – Highland Council unanimously condemns the incident after death toll rises to 22.
October 24, 2014 – Police say they believe that the birds were not deliberately targeted but were the victim of pest control measures
October 29, 2014 – Senior police officers forced to defend inquiry in front of Scottish Parliament rural affairs committee
November 10, 2014 – Highland MSP Dave Thompson calls for review of police handling of the case.
August 2, 2015 – Police dismiss claims they have been secretive about the investigation and say they are still active
April 20, 2017 – Police confirm the investigation is closed after reaching three year time limit.